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Configuring the ntfy server

The ntfy server can be configured in three ways: using a config file (typically at /etc/ntfy/server.yml, see server.yml), via command line arguments or using environment variables.

Quick start

By default, simply running ntfy serve will start the server at port 80. No configuration needed. Batteries included 😀. If everything works as it should, you'll see something like this:

$ ntfy serve
2021/11/30 19:59:08 Listening on :80

You can immediately start publishing messages, or subscribe via the Android app, the web UI, or simply via curl or your favorite HTTP client. To configure the server further, check out the config options table or simply type ntfy serve --help to get a list of command line options.

Example config

!!! info Definitely check out the server.yml file. It contains examples and detailed descriptions of all the settings.

The most basic settings are base-url (the external URL of the ntfy server), the HTTP/HTTPS listen address (listen-http and listen-https), and socket path (listen-unix). All the other things are additional features.

Here are a few working sample configs:

=== "server.yml (HTTP-only, with cache + attachments)" yaml base-url: "http://ntfy.example.com" cache-file: "/var/cache/ntfy/cache.db" attachment-cache-dir: "/var/cache/ntfy/attachments"

=== "server.yml (HTTP+HTTPS, with cache + attachments)" yaml base-url: "http://ntfy.example.com" listen-http: ":80" listen-https: ":443" key-file: "/etc/letsencrypt/live/ntfy.example.com.key" cert-file: "/etc/letsencrypt/live/ntfy.example.com.crt" cache-file: "/var/cache/ntfy/cache.db" attachment-cache-dir: "/var/cache/ntfy/attachments"

=== "server.yml (ntfy.sh config)" ``` yaml # All the things: Behind a proxy, Firebase, cache, attachments, # SMTP publishing & receiving

base-url: "https://ntfy.sh"
listen-http: "127.0.0.1:2586"
firebase-key-file: "/etc/ntfy/firebase.json"
cache-file: "/var/cache/ntfy/cache.db"
behind-proxy: true
attachment-cache-dir: "/var/cache/ntfy/attachments"
smtp-sender-addr: "email-smtp.us-east-2.amazonaws.com:587"
smtp-sender-user: "AKIDEADBEEFAFFE12345"
smtp-sender-pass: "Abd13Kf+sfAk2DzifjafldkThisIsNotARealKeyOMG."
smtp-sender-from: "ntfy@ntfy.sh"
smtp-server-listen: ":25"
smtp-server-domain: "ntfy.sh"
smtp-server-addr-prefix: "ntfy-"
keepalive-interval: "45s"
```

Message cache

If desired, ntfy can temporarily keep notifications in an in-memory or an on-disk cache. Caching messages for a short period of time is important to allow phones and other devices with brittle Internet connections to be able to retrieve notifications that they may have missed.

By default, ntfy keeps messages in-memory for 12 hours, which means that cached messages do not survive an application restart. You can override this behavior using the following config settings:

cache-file: if set, ntfy will store messages in a SQLite based cache (default is empty, which means in-memory cache). This is required if you'd like messages to be retained across restarts.
cache-duration: defines the duration for which messages are stored in the cache (default is 12h).

You can also entirely disable the cache by setting cache-duration to 0. When the cache is disabled, messages are only passed on to the connected subscribers, but never stored on disk or even kept in memory longer than is needed to forward the message to the subscribers.

Subscribers can retrieve cached messaging using the poll=1 parameter, as well as the since= parameter.

Attachments

If desired, you may allow users to upload and attach files to notifications. To enable this feature, you have to simply configure an attachment cache directory and a base URL (attachment-cache-dir, base-url). Once these options are set and the directory is writable by the server user, you can upload attachments via PUT.

By default, attachments are stored in the disk-cache for only 3 hours. The main reason for this is to avoid legal issues and such when hosting user controlled content. Typically, this is more than enough time for the user (or the auto download feature) to download the file. The following config options are relevant to attachments:

base-url is the root URL for the ntfy server; this is needed for the generated attachment URLs
attachment-cache-dir is the cache directory for attached files
attachment-total-size-limit is the size limit of the on-disk attachment cache (default: 5G)
attachment-file-size-limit is the per-file attachment size limit (e.g. 300k, 2M, 100M, default: 15M)
attachment-expiry-duration is the duration after which uploaded attachments will be deleted (e.g. 3h, 20h, default: 3h)

Here's an example config using mostly the defaults (except for the cache directory, which is empty by default):

=== "/etc/ntfy/server.yml (minimal)" yaml base-url: "https://ntfy.sh" attachment-cache-dir: "/var/cache/ntfy/attachments"

=== "/etc/ntfy/server.yml (all options)" yaml base-url: "https://ntfy.sh" attachment-cache-dir: "/var/cache/ntfy/attachments" attachment-total-size-limit: "5G" attachment-file-size-limit: "15M" attachment-expiry-duration: "3h" visitor-attachment-total-size-limit: "100M" visitor-attachment-daily-bandwidth-limit: "500M"

Please also refer to the rate limiting settings below, specifically visitor-attachment-total-size-limit and visitor-attachment-daily-bandwidth-limit. Setting these conservatively is necessary to avoid abuse.

Access control

By default, the ntfy server is open for everyone, meaning everyone can read and write to any topic (this is how ntfy.sh is configured). To restrict access to your own server, you can optionally configure authentication and authorization.

ntfy's auth is implemented with a simple SQLite-based backend. It implements two roles (user and admin) and per-topic read and write permissions using an access control list (ACL). Access control entries can be applied to users as well as the special everyone user (*), which represents anonymous API access.

To set up auth, simply configure the following two options:

auth-file is the user/access database; it is created automatically if it doesn't already exist; suggested location /var/lib/ntfy/user.db (easiest if deb/rpm package is used)
auth-default-access defines the default/fallback access if no access control entry is found; it can be set to read-write (default), read-only, write-only or deny-all.

Once configured, you can use the ntfy user command to add or modify users, and the ntfy access command lets you modify the access control list for specific users and topic patterns. Both of these commands directly edit the auth database (as defined in auth-file), so they only work on the server, and only if the user accessing them has the right permissions.

Users and roles

The ntfy user command allows you to add/remove/change users in the ntfy user database, as well as change passwords or roles (user or admin). In practice, you'll often just create one admin user with ntfy user add --role=admin ... and be done with all this (see example below).

Roles:

Role user (default): Users with this role have no special permissions. Manage access using ntfy access (see below).
Role admin: Users with this role can read/write to all topics. Granular access control is not necessary.

Example commands (type ntfy user --help or ntfy user COMMAND --help for more details):

ntfy user list                     # Shows list of users (alias: 'ntfy access')
ntfy user add phil                 # Add regular user phil  
ntfy user add --role=admin phil    # Add admin user phil
ntfy user del phil                 # Delete user phil
ntfy user change-pass phil         # Change password for user phil
ntfy user change-role phil admin   # Make user phil an admin

Access control list (ACL)

The access control list (ACL) manages access to topics for non-admin users, and for anonymous access (everyone/*). Each entry represents the access permissions for a user to a specific topic or topic pattern.

The ACL can be displayed or modified with the ntfy access command:

ntfy access                            # Shows access control list (alias: 'ntfy user list')
ntfy access USERNAME                   # Shows access control entries for USERNAME
ntfy access USERNAME TOPIC PERMISSION  # Allow/deny access for USERNAME to TOPIC

A USERNAME is an existing user, as created with ntfy user add (see users and roles), or the anonymous user everyone or *, which represents clients that access the API without username/password.

A TOPIC is either a specific topic name (e.g. mytopic, or phil_alerts), or a wildcard pattern that matches any number of topics (e.g. alerts_* or ben-*). Only the wildcard character * is supported. It stands for zero to any number of characters.

A PERMISSION is any of the following supported permissions:

read-write (alias: rw): Allows publishing messages to the given topic, as well as subscribing and reading messages
read-only (aliases: read, ro): Allows only subscribing and reading messages, but not publishing to the topic
write-only (aliases: write, wo): Allows only publishing to the topic, but not subscribing to it
deny (alias: none): Allows neither publishing nor subscribing to a topic

Example commands (type ntfy access --help for more details):

ntfy access                        # Shows entire access control list
ntfy access phil                   # Shows access for user phil
ntfy access phil mytopic rw        # Allow read-write access to mytopic for user phil
ntfy access everyone mytopic rw    # Allow anonymous read-write access to mytopic
ntfy access everyone "up*" write   # Allow anonymous write-only access to topics "up..."
ntfy access --reset                # Reset entire access control list
ntfy access --reset phil           # Reset all access for user phil
ntfy access --reset phil mytopic   # Reset access for user phil and topic mytopic

Example ACL:

$ ntfy access
user phil (admin)
- read-write access to all topics (admin role)
user ben (user)
- read-write access to topic garagedoor
- read-write access to topic alerts*
- read-only access to topic furnace
user * (anonymous)
- read-only access to topic announcements
- read-only access to topic server-stats
- no access to any (other) topics (server config)

In this example, phil has the role admin, so he has read-write access to all topics (no ACL entries are necessary). User ben has three topic-specific entries. He can read, but not write to topic furnace, and has read-write access to topic garagedoor and all topics starting with the word alerts (wildcards). Clients that are not authenticated (called */everyone) only have read access to the announcements and server-stats topics.

Example: Private instance

The easiest way to configure a private instance is to set auth-default-access to deny-all in the server.yml:

=== "/etc/ntfy/server.yml" yaml auth-file: "/var/lib/ntfy/user.db" auth-default-access: "deny-all"

After that, simply create an admin user:

$ ntfy user add --role=admin phil
password: mypass
confirm: mypass
user phil added with role admin

Once you've done that, you can publish and subscribe using Basic Auth with the given username/password. Be sure to use HTTPS to avoid eavesdropping and exposing your password. Here's a simple example:

=== "Command line (curl)" curl \ -u phil:mypass \ -d "Look ma, with auth" \ https://ntfy.example.com/mysecrets

=== "ntfy CLI" ntfy publish \ -u phil:mypass \ ntfy.example.com/mysecrets \ "Look ma, with auth"

=== "HTTP" ``` http POST /mysecrets HTTP/1.1 Host: ntfy.example.com Authorization: Basic cGhpbDpteXBhc3M=

Look ma, with auth
```

=== "JavaScript" javascript fetch('https://ntfy.example.com/mysecrets', { method: 'POST', // PUT works too body: 'Look ma, with auth', headers: { 'Authorization': 'Basic cGhpbDpteXBhc3M=' } })

=== "Go" go req, _ := http.NewRequest("POST", "https://ntfy.example.com/mysecrets", strings.NewReader("Look ma, with auth")) req.Header.Set("Authorization", "Basic cGhpbDpteXBhc3M=") http.DefaultClient.Do(req)

=== "Python" python requests.post("https://ntfy.example.com/mysecrets", data="Look ma, with auth", headers={ "Authorization": "Basic cGhpbDpteXBhc3M=" })

=== "PHP" php-inline file_get_contents('https://ntfy.example.com/mysecrets', false, stream_context_create([ 'http' => [ 'method' => 'POST', // PUT also works 'header' => 'Content-Type: text/plain\r\n' . 'Authorization: Basic cGhpbDpteXBhc3M=', 'content' => 'Look ma, with auth' ] ]));

E-mail notifications

To allow forwarding messages via e-mail, you can configure an SMTP server for outgoing messages. Once configured, you can set the X-Email header to send messages via e-mail (e.g. curl -d "hi there" -H "X-Email: phil@example.com" ntfy.sh/mytopic).

As of today, only SMTP servers with PLAIN auth and STARTLS are supported. To enable e-mail sending, you must set the following settings:

base-url is the root URL for the ntfy server; this is needed for e-mail footer
smtp-sender-addr is the hostname:port of the SMTP server
smtp-sender-user and smtp-sender-pass are the username and password of the SMTP user
smtp-sender-from is the e-mail address of the sender

Here's an example config using Amazon SES for outgoing mail (this is how it is configured for ntfy.sh):

=== "/etc/ntfy/server.yml" yaml base-url: "https://ntfy.sh" smtp-sender-addr: "email-smtp.us-east-2.amazonaws.com:587" smtp-sender-user: "AKIDEADBEEFAFFE12345" smtp-sender-pass: "Abd13Kf+sfAk2DzifjafldkThisIsNotARealKeyOMG." smtp-sender-from: "ntfy@ntfy.sh"

Please also refer to the rate limiting settings below, specifically visitor-email-limit-burst and visitor-email-limit-burst. Setting these conservatively is necessary to avoid abuse.

E-mail publishing

To allow publishing messages via e-mail, ntfy can run a lightweight SMTP server for incoming messages. Once configured, users can send emails to a topic e-mail address (e.g. mytopic@ntfy.sh or myprefix-mytopic@ntfy.sh) to publish messages to a topic. This is useful for e-mail based integrations such as for statuspage.io (though these days most services also support webhooks and HTTP calls).

To configure the SMTP server, you must at least set smtp-server-listen and smtp-server-domain:

smtp-server-listen defines the IP address and port the SMTP server will listen on, e.g. :25 or 1.2.3.4:25
smtp-server-domain is the e-mail domain, e.g. ntfy.sh (must be identical to MX record, see below)
smtp-server-addr-prefix is an optional prefix for the e-mail addresses to prevent spam. If set to ntfy-, for instance, only e-mails to ntfy-$topic@ntfy.sh will be accepted. If this is not set, all emails to $topic@ntfy.sh will be accepted (which may obviously be a spam problem).

Here's an example config (this is how it is configured for ntfy.sh):

=== "/etc/ntfy/server.yml" yaml smtp-server-listen: ":25" smtp-server-domain: "ntfy.sh" smtp-server-addr-prefix: "ntfy-"

In addition to configuring the ntfy server, you have to create two DNS records (an MX record and a corresponding A record), so incoming mail will find its way to your server. Here's an example of how ntfy.sh is configured (in Amazon Route 53):

![DNS records for incoming mail](static/img/screenshot-email-publishing-dns.png){ width=600 }

DNS records for incoming mail

You can check if everything is working correctly by sending an email as raw SMTP via nc. Create a text file, e.g. email.txt

EHLO example.com
MAIL FROM: phil@example.com
RCPT TO: ntfy-mytopic@ntfy.sh
DATA
Subject: Email for you
Content-Type: text/plain; charset="UTF-8"

Hello from 🇩🇪
.

And then send the mail via nc like this. If you see any lines starting with 451, those are errors from the ntfy server. Read them carefully.

$ cat email.txt | nc -N ntfy.sh 25
220 ntfy.sh ESMTP Service Ready
250-Hello example.com
...
250 2.0.0 Roger, accepting mail from <phil@example.com>
250 2.0.0 I'll make sure <ntfy-mytopic@ntfy.sh> gets this

As for the DNS setup, be sure to verify that dig MX and dig A are returning results similar to this:

$ dig MX ntfy.sh +short 
10 mx1.ntfy.sh.
$ dig A mx1.ntfy.sh +short 
3.139.215.220

Behind a proxy (TLS, etc.)

!!! warning If you are running ntfy behind a proxy, you must set the behind-proxy flag. Otherwise, all visitors are rate limited as if they are one.

It may be desirable to run ntfy behind a proxy (e.g. nginx, HAproxy or Apache), so you can provide TLS certificates using Let's Encrypt using certbot, or simply because you'd like to share the ports (80/443) with other services. Whatever your reasons may be, there are a few things to consider.

If you are running ntfy behind a proxy, you should set the behind-proxy flag. This will instruct the rate limiting logic to use the X-Forwarded-For header as the primary identifier for a visitor, as opposed to the remote IP address. If the behind-proxy flag is not set, all visitors will be counted as one, because from the perspective of the ntfy server, they all share the proxy's IP address.

=== "/etc/ntfy/server.yml" yaml # Tell ntfy to use "X-Forwarded-For" to identify visitors behind-proxy: true

TLS/SSL

ntfy supports HTTPS/TLS by setting the listen-https config option. However, if you are behind a proxy, it is recommended that TLS/SSL termination is done by the proxy itself (see below).

I highly recommend using certbot. I use it with the dns-route53 plugin, which lets you use AWS Route 53 as the challenge. That's much easier than using the HTTP challenge. I've found this guide to be incredibly helpful.

nginx/Apache2/caddy

For your convenience, here's a working config that'll help configure things behind a proxy. Be sure to enable WebSockets by forwarding the Connection and Upgrade headers accordingly.

In this example, ntfy runs on :2586 and we proxy traffic to it. We also redirect HTTP to HTTPS for GET requests against a topic or the root domain:

=== "nginx (/etc/nginx/sites-*/ntfy)" ``` server { listen 80; server_name ntfy.sh;

  location / {
    # Redirect HTTP to HTTPS, but only for GET topic addresses, since we want 
    # it to work with curl without the annoying https:// prefix
    set $redirect_https "";
    if ($request_method = GET) {
      set $redirect_https "yes";
    }
    if ($request_uri ~* "^/([-_a-z0-9]{0,64}$|docs/|static/)") {
      set $redirect_https "${redirect_https}yes";
    }
    if ($redirect_https = "yesyes") {
      return 302 https://$http_host$request_uri$is_args$query_string;
    }

    proxy_pass http://127.0.0.1:2586;
    proxy_http_version 1.1;

    proxy_buffering off;
    proxy_request_buffering off;
    proxy_redirect off;
 
    proxy_set_header Host $http_host;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

    proxy_connect_timeout 3m;
    proxy_send_timeout 3m;
    proxy_read_timeout 3m;

    client_max_body_size 20m; # Must be >= attachment-file-size-limit in /etc/ntfy/server.yml
  }
}

server {
  listen 443 ssl;
  server_name ntfy.sh;

  ssl_session_cache builtin:1000 shared:SSL:10m;
  ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
  ssl_ciphers HIGH:!aNULL:!eNULL:!EXPORT:!CAMELLIA:!DES:!MD5:!PSK:!RC4;
  ssl_prefer_server_ciphers on;

  ssl_certificate /etc/letsencrypt/live/ntfy.sh/fullchain.pem;
  ssl_certificate_key /etc/letsencrypt/live/ntfy.sh/privkey.pem;

  location / {
    proxy_pass http://127.0.0.1:2586;
    proxy_http_version 1.1;

    proxy_buffering off;
    proxy_request_buffering off;
    proxy_redirect off;
 
    proxy_set_header Host $http_host;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

    proxy_connect_timeout 3m;
    proxy_send_timeout 3m;
    proxy_read_timeout 3m;
    
    client_max_body_size 20m; # Must be >= attachment-file-size-limit in /etc/ntfy/server.yml
  }
}
```

=== "Apache2 (/etc/apache2/sites-*/ntfy.conf)" ``` <VirtualHost *:80> ServerName ntfy.sh

    # Proxy connections to ntfy (requires "a2enmod proxy")
    ProxyPass / http://127.0.0.1:2586/
    ProxyPassReverse / http://127.0.0.1:2586/

    SetEnv proxy-nokeepalive 1
    SetEnv proxy-sendchunked 1

    # Higher than the max message size of 4096 bytes
    LimitRequestBody 102400

    # Enable mod_rewrite (requires "a2enmod rewrite")
    RewriteEngine on

    # WebSockets support (requires "a2enmod rewrite proxy_wstunnel")
    RewriteCond %{HTTP:Upgrade} websocket [NC]
    RewriteCond %{HTTP:Connection} upgrade [NC]
    RewriteRule ^/?(.*) "ws://127.0.0.1:2586/$1" [P,L]
    
    # Redirect HTTP to HTTPS, but only for GET topic addresses, since we want 
    # it to work with curl without the annoying https:// prefix 
    RewriteCond %{REQUEST_METHOD} GET
    RewriteRule ^/([-_A-Za-z0-9]{0,64})$ https://%{SERVER_NAME}/$1 [R,L]
</VirtualHost>

<VirtualHost *:443>
    ServerName ntfy.sh
    
    SSLEngine on
    SSLCertificateFile /etc/letsencrypt/live/ntfy.sh/fullchain.pem
    SSLCertificateKeyFile /etc/letsencrypt/live/ntfy.sh/privkey.pem
    Include /etc/letsencrypt/options-ssl-apache.conf

    # Proxy connections to ntfy (requires "a2enmod proxy")
    ProxyPass / http://127.0.0.1:2586/
    ProxyPassReverse / http://127.0.0.1:2586/

    SetEnv proxy-nokeepalive 1
    SetEnv proxy-sendchunked 1

    # Higher than the max message size of 4096 bytes 
    LimitRequestBody 102400

    # Enable mod_rewrite (requires "a2enmod rewrite")
    RewriteEngine on

    # WebSockets support (requires "a2enmod rewrite proxy_wstunnel")
    RewriteCond %{HTTP:Upgrade} websocket [NC]
    RewriteCond %{HTTP:Connection} upgrade [NC]
    RewriteRule ^/?(.*) "ws://127.0.0.1:2586/$1" [P,L] 
</VirtualHost>
```

=== "caddy" ``` # Note that this config is most certainly incomplete. Please help out and let me know what's missing # via Discord/Matrix or in a GitHub issue.

ntfy.sh, http://nfty.sh {
    reverse_proxy 127.0.0.1:2586

    # Redirect HTTP to HTTPS, but only for GET topic addresses, since we want
    # it to work with curl without the annoying https:// prefix
    @httpget {
        protocol http
        method GET
        path_regexp ^/([-_a-z0-9]{0,64}$|docs/|static/)
    }
    redir @httpget https://{host}{uri}
}
```

Firebase (FCM)

!!! info Using Firebase is optional and only works if you modify and build your own Android .apk. For a self-hosted instance, it's easier to just not bother with FCM.

Firebase Cloud Messaging (FCM) is the Google approved way to send push messages to Android devices. FCM is the only method that an Android app can receive messages without having to run a foreground service.

For the main host ntfy.sh, the ntfy Android app uses Firebase to send messages to the device. For other hosts, instant delivery is used and FCM is not involved.

To configure FCM for your self-hosted instance of the ntfy server, follow these steps:

Sign up for a Firebase account
Create a Firebase app and download the key file (e.g. myapp-firebase-adminsdk-...json)
Place the key file in /etc/ntfy, set the firebase-key-file in server.yml accordingly and restart the ntfy server
Build your own Android .apk following these instructions

Example:

# If set, also publish messages to a Firebase Cloud Messaging (FCM) topic for your app.
# This is optional and only required to support Android apps (which don't allow background services anymore).
#
firebase-key-file: "/etc/ntfy/ntfy-sh-firebase-adminsdk-ahnce-9f4d6f14b5.json"

iOS instant notifications

Unlike Android, iOS heavily restricts background processing, which sadly makes it impossible to implement instant push notifications without a central server.

To still support instant notifications on iOS through your self-hosted ntfy server, you have to forward so called poll_request messages to the main ntfy.sh server (or any upstream server that's APNS/Firebase connected, if you build your own iOS app), which will then forward it to Firebase/APNS.

To configure it, simply set upstream-base-url like so:

upstream-base-url: "https://ntfy.sh"

If set, all incoming messages will publish a poll request to the configured upstream server, containing the message ID of the original message, instructing the iOS app to poll this server for the actual message contents.

If upstream-base-url is not set, notifications will still eventually get to your device, but delivery can take hours, depending on the state of the phone. If you are using your phone, it shouldn't take more than 20-30 minutes though.

In case you're curious, here's an example of the entire flow:

In the iOS app, you subscribe to https://ntfy.example.com/mytopic
The app subscribes to the Firebase topic 6de73be8dfb7d69e... (the SHA256 of the topic URL)
When you publish a message to https://ntfy.example.com/mytopic, your ntfy server will publish a poll request to https://ntfy.sh/6de73be8dfb7d69e... (passing the message ID in the X-Poll-ID header)
The ntfy.sh server publishes the message to Firebase, which forwards it to APNS, which forwards it to your iOS device
Your iOS device receives the poll request, and fetches the actual message from your server, and then displays it

Rate limiting

!!! info Be aware that if you are running ntfy behind a proxy, you must set the behind-proxy flag. Otherwise, all visitors are rate limited as if they are one.

By default, ntfy runs without authentication, so it is vitally important that we protect the server from abuse or overload. There are various limits and rate limits in place that you can use to configure the server:

Global limit: A global limit applies across all visitors (IPs, clients, users)
Visitor limit: A visitor limit only applies to a certain visitor. A visitor is identified by its IP address (or the X-Forwarded-For header if behind-proxy is set). All config options that start with the word visitor apply only on a per-visitor basis.

During normal usage, you shouldn't encounter these limits at all, and even if you burst a few requests or emails (e.g. when you reconnect after a connection drop), it shouldn't have any effect.

General limits

Let's do the easy limits first:

global-topic-limit defines the total number of topics before the server rejects new topics. It defaults to 15,000.
visitor-subscription-limit is the number of subscriptions (open connections) per visitor. This value defaults to 30.

Request limits

In addition to the limits above, there is a requests/second limit per visitor for all sensitive GET/PUT/POST requests. This limit uses a token bucket (using Go's rate package):

Each visitor has a bucket of 60 requests they can fire against the server (defined by visitor-request-limit-burst). After the 60, new requests will encounter a 429 Too Many Requests response. The visitor request bucket is refilled at a rate of one request every 5s (defined by visitor-request-limit-replenish)

visitor-request-limit-burst is the initial bucket of requests each visitor has. This defaults to 60.
visitor-request-limit-replenish is the rate at which the bucket is refilled (one request per x). Defaults to 5s.
visitor-request-limit-exempt-hosts is a comma-separated list of hostnames and IPs to be exempt from request rate limiting; hostnames are resolved at the time the server is started. Defaults to an empty list.

Attachment limits

Aside from the global file size and total attachment cache limits (see above), there are two relevant per-visitor limits:

visitor-attachment-total-size-limit is the total storage limit used for attachments per visitor. It defaults to 100M. The per-visitor storage is automatically decreased as attachments expire. External attachments (attached via X-Attach, see publishing docs) do not count here.
visitor-attachment-daily-bandwidth-limit is the total daily attachment download/upload bandwidth limit per visitor, including PUT and GET requests. This is to protect your precious bandwidth from abuse, since egress costs money in most cloud providers. This defaults to 500M.

E-mail limits

Similarly to the request limit, there is also an e-mail limit (only relevant if e-mail notifications are enabled):

visitor-email-limit-burst is the initial bucket of emails each visitor has. This defaults to 16.
visitor-email-limit-replenish is the rate at which the bucket is refilled (one email per x). Defaults to 1h.

Tuning for scale

If you're running ntfy for your home server, you probably don't need to worry about scale at all. In its default config, if it's not behind a proxy, the ntfy server can keep about as many connections as the open file limit allows. This limit is typically called nofile. Other than that, RAM and CPU are obviously relevant. You may also want to check out this discussion on Reddit.

Depending on how you run it, here are a few limits that are relevant:

For systemd services

If you're running ntfy in a systemd service (e.g. for .deb/.rpm packages), the main limiting factor is the LimitNOFILE setting in the systemd unit. The default open files limit for ntfy.service is 10,000. You can override it by creating a /etc/systemd/system/ntfy.service.d/override.conf file. As far as I can tell, /etc/security/limits.conf is not relevant.

=== "/etc/systemd/system/ntfy.service.d/override.conf" # Allow 20,000 ntfy connections (and give room for other file handles) [Service] LimitNOFILE=20500

Outside of systemd

If you're running outside systemd, you may want to adjust your /etc/security/limits.conf file to increase the nofile setting. Here's an example that increases the limit to 5,000. You can find out the current setting by running ulimit -n, or manually override it temporarily by running ulimit -n 50000.

=== "/etc/security/limits.conf" # Increase open files limit globally * hard nofile 20500

Proxy limits (nginx, Apache2)

If you are running behind a proxy (e.g. nginx, Apache), the open files limit of the proxy is also relevant. So if your proxy runs inside of systemd, increase the limits in systemd for the proxy. Typically, the proxy open files limit has to be double the number of how many connections you'd like to support, because the proxy has to maintain the client connection and the connection to ntfy.

=== "/etc/nginx/nginx.conf" events { # Allow 40,000 proxy connections (2x of the desired ntfy connection count; # and give room for other file handles) worker_connections 40500; }

=== "/etc/systemd/system/nginx.service.d/override.conf" # Allow 40,000 proxy connections (2x of the desired ntfy connection count; # and give room for other file handles) [Service] LimitNOFILE=40500

Banning bad actors (fail2ban)

If you put stuff on the Internet, bad actors will try to break them or break in. fail2ban and nginx's ngx_http_limit_req_module module can be used to ban client IPs if they misbehave. This is on top of the rate limiting inside the ntfy server.

Here's an example for how ntfy.sh is configured, following the instructions from two tutorials (here and here):

=== "/etc/nginx/nginx.conf" http { limit_req_zone $binary_remote_addr zone=one:10m rate=1r/s; }

=== "/etc/nginx/sites-enabled/ntfy.sh" # For each server/location block server { location / { limit_req zone=one burst=1000 nodelay; } }

=== "/etc/fail2ban/filter.d/nginx-req-limit.conf" [Definition] failregex = limiting requests, excess:.* by zone.*client: <HOST> ignoreregex =

=== "/etc/fail2ban/jail.local" [nginx-req-limit] enabled = true filter = nginx-req-limit action = iptables-multiport[name=ReqLimit, port="http,https", protocol=tcp] logpath = /var/log/nginx/error.log findtime = 600 bantime = 7200 maxretry = 10

Config options

Each config option can be set in the config file /etc/ntfy/server.yml (e.g. listen-http: :80) or as a CLI option (e.g. --listen-http :80. Here's a list of all available options. Alternatively, you can set an environment variable before running the ntfy command (e.g. export NTFY_LISTEN_HTTP=:80).

!!! info All config options can also be defined in the server.yml file using underscores instead of dashes, e.g. cache_duration and cache-duration are both supported. This is to support stricter YAML parsers that do not support dashes.

Config option	Env variable	Format	Default	Description
`base-url`	`NTFY_BASE_URL`	URL	-	Public facing base URL of the service (e.g. `https://ntfy.sh`)
`listen-http`	`NTFY_LISTEN_HTTP`	`[host]:port`	`:80`	Listen address for the HTTP web server
`listen-https`	`NTFY_LISTEN_HTTPS`	`[host]:port`	-	Listen address for the HTTPS web server. If set, you also need to set `key-file` and `cert-file`.
`listen-unix`	`NTFY_LISTEN_UNIX`	filename	-	Path to a Unix socket to listen on
`key-file`	`NTFY_KEY_FILE`	filename	-	HTTPS/TLS private key file, only used if `listen-https` is set.
`cert-file`	`NTFY_CERT_FILE`	filename	-	HTTPS/TLS certificate file, only used if `listen-https` is set.
`firebase-key-file`	`NTFY_FIREBASE_KEY_FILE`	filename	-	If set, also publish messages to a Firebase Cloud Messaging (FCM) topic for your app. This is optional and only required to save battery when using the Android app. See Firebase (FCM.
`cache-file`	`NTFY_CACHE_FILE`	filename	-	If set, messages are cached in a local SQLite database instead of only in-memory. This allows for service restarts without losing messages in support of the since= parameter. See message cache.
`cache-duration`	`NTFY_CACHE_DURATION`	duration	12h	Duration for which messages will be buffered before they are deleted. This is required to support the `since=...` and `poll=1` parameter. Set this to `0` to disable the cache entirely.
`auth-file`	`NTFY_AUTH_FILE`	filename	-	Auth database file used for access control. If set, enables authentication and access control. See access control.
`auth-default-access`	`NTFY_AUTH_DEFAULT_ACCESS`	`read-write`, `read-only`, `write-only`, `deny-all`	`read-write`	Default permissions if no matching entries in the auth database are found. Default is `read-write`.
`behind-proxy`	`NTFY_BEHIND_PROXY`	bool	false	If set, the X-Forwarded-For header is used to determine the visitor IP address instead of the remote address of the connection.
`attachment-cache-dir`	`NTFY_ATTACHMENT_CACHE_DIR`	directory	-	Cache directory for attached files. To enable attachments, this has to be set.
`attachment-total-size-limit`	`NTFY_ATTACHMENT_TOTAL_SIZE_LIMIT`	size	5G	Limit of the on-disk attachment cache directory. If the limits is exceeded, new attachments will be rejected.
`attachment-file-size-limit`	`NTFY_ATTACHMENT_FILE_SIZE_LIMIT`	size	15M	Per-file attachment size limit (e.g. 300k, 2M, 100M). Larger attachment will be rejected.
`attachment-expiry-duration`	`NTFY_ATTACHMENT_EXPIRY_DURATION`	duration	3h	Duration after which uploaded attachments will be deleted (e.g. 3h, 20h). Strongly affects `visitor-attachment-total-size-limit`.
`smtp-sender-addr`	`NTFY_SMTP_SENDER_ADDR`	`host:port`	-	SMTP server address to allow email sending
`smtp-sender-user`	`NTFY_SMTP_SENDER_USER`	string	-	SMTP user; only used if e-mail sending is enabled
`smtp-sender-pass`	`NTFY_SMTP_SENDER_PASS`	string	-	SMTP password; only used if e-mail sending is enabled
`smtp-sender-from`	`NTFY_SMTP_SENDER_FROM`	e-mail address	-	SMTP sender e-mail address; only used if e-mail sending is enabled
`smtp-server-listen`	`NTFY_SMTP_SERVER_LISTEN`	`[ip]:port`	-	Defines the IP address and port the SMTP server will listen on, e.g. `:25` or `1.2.3.4:25`
`smtp-server-domain`	`NTFY_SMTP_SERVER_DOMAIN`	domain name	-	SMTP server e-mail domain, e.g. `ntfy.sh`
`smtp-server-addr-prefix`	`NTFY_SMTP_SERVER_ADDR_PREFIX`	`[ip]:port`	-	Optional prefix for the e-mail addresses to prevent spam, e.g. `ntfy-`
`keepalive-interval`	`NTFY_KEEPALIVE_INTERVAL`	duration	45s	Interval in which keepalive messages are sent to the client. This is to prevent intermediaries closing the connection for inactivity. Note that the Android app has a hardcoded timeout at 77s, so it should be less than that.
`manager-interval`	`$NTFY_MANAGER_INTERVAL`	duration	1m	Interval in which the manager prunes old messages, deletes topics and prints the stats.
`web-root`	`NTFY_WEB_ROOT`	`app`, `home` or `disable`	`app`	Sets web root to landing page (home), web app (app) or disables the web app entirely (disable)
`global-topic-limit`	`NTFY_GLOBAL_TOPIC_LIMIT`	number	15,000	Rate limiting: Total number of topics before the server rejects new topics.
`visitor-subscription-limit`	`NTFY_VISITOR_SUBSCRIPTION_LIMIT`	number	30	Rate limiting: Number of subscriptions per visitor (IP address)
`visitor-attachment-total-size-limit`	`NTFY_VISITOR_ATTACHMENT_TOTAL_SIZE_LIMIT`	size	100M	Rate limiting: Total storage limit used for attachments per visitor, for all attachments combined. Storage is freed after attachments expire. See `attachment-expiry-duration`.
`visitor-attachment-daily-bandwidth-limit`	`NTFY_VISITOR_ATTACHMENT_DAILY_BANDWIDTH_LIMIT`	size	500M	Rate limiting: Total daily attachment download/upload traffic limit per visitor. This is to protect your bandwidth costs from exploding.
`visitor-request-limit-burst`	`NTFY_VISITOR_REQUEST_LIMIT_BURST`	number	60	Rate limiting: Allowed GET/PUT/POST requests per second, per visitor. This setting is the initial bucket of requests each visitor has
`visitor-request-limit-replenish`	`NTFY_VISITOR_REQUEST_LIMIT_REPLENISH`	duration	5s	Rate limiting: Strongly related to `visitor-request-limit-burst`: The rate at which the bucket is refilled
`visitor-request-limit-exempt-hosts`	`NTFY_VISITOR_REQUEST_LIMIT_EXEMPT_HOSTS`	comma-separated host/IP list	-	Rate limiting: List of hostnames and IPs to be exempt from request rate limiting
`visitor-email-limit-burst`	`NTFY_VISITOR_EMAIL_LIMIT_BURST`	number	16	Rate limiting:Initial limit of e-mails per visitor
`visitor-email-limit-replenish`	`NTFY_VISITOR_EMAIL_LIMIT_REPLENISH`	duration	1h	Rate limiting: Strongly related to `visitor-email-limit-burst`: The rate at which the bucket is refilled

The format for a duration is: <number>(smh), e.g. 30s, 20m or 1h.
The format for a size is: <number>(GMK), e.g. 1G, 200M or 4000k.

Command line options

$ ntfy serve --help
NAME:
   ntfy serve - Run the ntfy server

USAGE:
   ntfy serve [OPTIONS..]

CATEGORY:
   Server commands

DESCRIPTION:
   Run the ntfy server and listen for incoming requests
   
   The command will load the configuration from /etc/ntfy/server.yml. Config options can 
   be overridden using the command line options.
   
   Examples:
     ntfy serve                      # Starts server in the foreground (on port 80)
     ntfy serve --listen-http :8080  # Starts server with alternate port

OPTIONS:
   --config value, -c value                                                                            config file (default: /etc/ntfy/server.yml) [$NTFY_CONFIG_FILE]
   --base-url value, --base_url value, -B value                                                        externally visible base URL for this host (e.g. https://ntfy.sh) [$NTFY_BASE_URL]
   --listen-http value, --listen_http value, -l value                                                  ip:port used to as HTTP listen address (default: ":80") [$NTFY_LISTEN_HTTP]
   --listen-https value, --listen_https value, -L value                                                ip:port used to as HTTPS listen address [$NTFY_LISTEN_HTTPS]
   --listen-unix value, --listen_unix value, -U value                                                  listen on unix socket path [$NTFY_LISTEN_UNIX]
   --key-file value, --key_file value, -K value                                                        private key file, if listen-https is set [$NTFY_KEY_FILE]
   --cert-file value, --cert_file value, -E value                                                      certificate file, if listen-https is set [$NTFY_CERT_FILE]
   --firebase-key-file value, --firebase_key_file value, -F value                                      Firebase credentials file; if set additionally publish to FCM topic [$NTFY_FIREBASE_KEY_FILE]
   --cache-file value, --cache_file value, -C value                                                    cache file used for message caching [$NTFY_CACHE_FILE]
   --cache-duration since, --cache_duration since, -b since                                            buffer messages for this time to allow since requests (default: 12h0m0s) [$NTFY_CACHE_DURATION]
   --auth-file value, --auth_file value, -H value                                                      auth database file used for access control [$NTFY_AUTH_FILE]
   --auth-default-access value, --auth_default_access value, -p value                                  default permissions if no matching entries in the auth database are found (default: "read-write") [$NTFY_AUTH_DEFAULT_ACCESS]
   --attachment-cache-dir value, --attachment_cache_dir value                                          cache directory for attached files [$NTFY_ATTACHMENT_CACHE_DIR]
   --attachment-total-size-limit value, --attachment_total_size_limit value, -A value                  limit of the on-disk attachment cache (default: 5G) [$NTFY_ATTACHMENT_TOTAL_SIZE_LIMIT]
   --attachment-file-size-limit value, --attachment_file_size_limit value, -Y value                    per-file attachment size limit (e.g. 300k, 2M, 100M) (default: 15M) [$NTFY_ATTACHMENT_FILE_SIZE_LIMIT]
   --attachment-expiry-duration value, --attachment_expiry_duration value, -X value                    duration after which uploaded attachments will be deleted (e.g. 3h, 20h) (default: 3h) [$NTFY_ATTACHMENT_EXPIRY_DURATION]
   --keepalive-interval value, --keepalive_interval value, -k value                                    interval of keepalive messages (default: 45s) [$NTFY_KEEPALIVE_INTERVAL]
   --manager-interval value, --manager_interval value, -m value                                        interval of for message pruning and stats printing (default: 1m0s) [$NTFY_MANAGER_INTERVAL]
   --web-root value, --web_root value                                                                  sets web root to landing page (home), web app (app) or disabled (disable) (default: "app") [$NTFY_WEB_ROOT]
   --smtp-sender-addr value, --smtp_sender_addr value                                                  SMTP server address (host:port) for outgoing emails [$NTFY_SMTP_SENDER_ADDR]
   --smtp-sender-user value, --smtp_sender_user value                                                  SMTP user (if e-mail sending is enabled) [$NTFY_SMTP_SENDER_USER]
   --smtp-sender-pass value, --smtp_sender_pass value                                                  SMTP password (if e-mail sending is enabled) [$NTFY_SMTP_SENDER_PASS]
   --smtp-sender-from value, --smtp_sender_from value                                                  SMTP sender address (if e-mail sending is enabled) [$NTFY_SMTP_SENDER_FROM]
   --smtp-server-listen value, --smtp_server_listen value                                              SMTP server address (ip:port) for incoming emails, e.g. :25 [$NTFY_SMTP_SERVER_LISTEN]
   --smtp-server-domain value, --smtp_server_domain value                                              SMTP domain for incoming e-mail, e.g. ntfy.sh [$NTFY_SMTP_SERVER_DOMAIN]
   --smtp-server-addr-prefix value, --smtp_server_addr_prefix value                                    SMTP email address prefix for topics to prevent spam (e.g. 'ntfy-') [$NTFY_SMTP_SERVER_ADDR_PREFIX]
   --global-topic-limit value, --global_topic_limit value, -T value                                    total number of topics allowed (default: 15000) [$NTFY_GLOBAL_TOPIC_LIMIT]
   --visitor-subscription-limit value, --visitor_subscription_limit value                              number of subscriptions per visitor (default: 30) [$NTFY_VISITOR_SUBSCRIPTION_LIMIT]
   --visitor-attachment-total-size-limit value, --visitor_attachment_total_size_limit value            total storage limit used for attachments per visitor (default: "100M") [$NTFY_VISITOR_ATTACHMENT_TOTAL_SIZE_LIMIT]
   --visitor-attachment-daily-bandwidth-limit value, --visitor_attachment_daily_bandwidth_limit value  total daily attachment download/upload bandwidth limit per visitor (default: "500M") [$NTFY_VISITOR_ATTACHMENT_DAILY_BANDWIDTH_LIMIT]
   --visitor-request-limit-burst value, --visitor_request_limit_burst value                            initial limit of requests per visitor (default: 60) [$NTFY_VISITOR_REQUEST_LIMIT_BURST]
   --visitor-request-limit-replenish value, --visitor_request_limit_replenish value                    interval at which burst limit is replenished (one per x) (default: 5s) [$NTFY_VISITOR_REQUEST_LIMIT_REPLENISH]
   --visitor-request-limit-exempt-hosts value, --visitor_request_limit_exempt_hosts value              hostnames and/or IP addresses of hosts that will be exempt from the visitor request limit [$NTFY_VISITOR_REQUEST_LIMIT_EXEMPT_HOSTS]
   --visitor-email-limit-burst value, --visitor_email_limit_burst value                                initial limit of e-mails per visitor (default: 16) [$NTFY_VISITOR_EMAIL_LIMIT_BURST]
   --visitor-email-limit-replenish value, --visitor_email_limit_replenish value                        interval at which burst limit is replenished (one per x) (default: 1h0m0s) [$NTFY_VISITOR_EMAIL_LIMIT_REPLENISH]
   --behind-proxy, --behind_proxy, -P                                                                  if set, use X-Forwarded-For header to determine visitor IP address (for rate limiting) (default: false) [$NTFY_BEHIND_PROXY]
   --help, -h                                                                                          show help (default: false)

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