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ntfy/docs/config.md

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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.

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.

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
  • 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

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. 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 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 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

    SetEnv proxy-nokeepalive 1
    SetEnv proxy-sendchunked 1
    
    ProxyPass / http://127.0.0.1:2586/
    ProxyPassReverse / http://127.0.0.1:2586/
    
    # Higher than the max message size of 4096 bytes
    LimitRequestBody 102400
    
    # Redirect HTTP to HTTPS, but only for GET topic addresses, since we want 
    # it to work with curl without the annoying https:// prefix 
    RewriteEngine on
    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
    
    SetEnv proxy-nokeepalive 1
    SetEnv proxy-sendchunked 1
    
    ProxyPass / http://127.0.0.1:2586/
    ProxyPassReverse / http://127.0.0.1:2586/
    
    # Higher than the max message size of 4096 bytes 
    LimitRequestBody 102400
    
    # Redirect HTTP to HTTPS, but only for GET topic addresses, since we want 
    # it to work with curl without the annoying https:// prefix 
    RewriteEngine on
    RewriteCond %{REQUEST_METHOD} GET
    RewriteRule ^/([-_A-Za-z0-9]{0,64})$ https://%{SERVER_NAME}/$1 [R,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 {
    reverse_proxy 127.0.0.1:2586
}
http://nfty.sh {
    reverse_proxy 127.0.0.1:2586
}
```

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:

  1. Sign up for a Firebase account
  2. Create a Firebase app and download the key file (e.g. myapp-firebase-adminsdk-...json)
  3. Place the key file in /etc/ntfy, set the firebase-key-file in server.yml accordingly and restart the ntfy server
  4. 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"

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 10s (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 10s.

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).

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.
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.
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 55s 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.
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 10s Rate limiting: Strongly related to visitor-request-limit-burst: The rate at which the bucket is refilled
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..]

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) [$NTFY_CONFIG_FILE]
   --base-url value, -B value                        externally visible base URL for this host (e.g. https://ntfy.sh) [$NTFY_BASE_URL]
   --listen-http value, -l value                     ip:port used to as HTTP listen address (default: ":80") [$NTFY_LISTEN_HTTP]
   --listen-https value, -L value                    ip:port used to as HTTPS listen address [$NTFY_LISTEN_HTTPS]
   --key-file value, -K value                        private key file, if listen-https is set [$NTFY_KEY_FILE]
   --cert-file value, -E value                       certificate file, if listen-https is set [$NTFY_CERT_FILE]
   --firebase-key-file value, -F value               Firebase credentials file; if set additionally publish to FCM topic [$NTFY_FIREBASE_KEY_FILE]
   --cache-file value, -C value                      cache file used for message caching [$NTFY_CACHE_FILE]
   --cache-duration since, -b since                  buffer messages for this time to allow since requests (default: 12h0m0s) [$NTFY_CACHE_DURATION]
   --attachment-cache-dir value                      cache directory for attached files [$NTFY_ATTACHMENT_CACHE_DIR]
   --attachment-total-size-limit value, -A value     limit of the on-disk attachment cache (default: 5G) [$NTFY_ATTACHMENT_TOTAL_SIZE_LIMIT]
   --attachment-file-size-limit value, -Y value      per-file attachment size limit (e.g. 300k, 2M, 100M) (default: 15M) [$NTFY_ATTACHMENT_FILE_SIZE_LIMIT]
   --attachment-expiry-duration value, -X value      duration after which uploaded attachments will be deleted (e.g. 3h, 20h) (default: 3h) [$NTFY_ATTACHMENT_EXPIRY_DURATION]
   --keepalive-interval value, -k value              interval of keepalive messages (default: 55s) [$NTFY_KEEPALIVE_INTERVAL]
   --manager-interval value, -m value                interval of for message pruning and stats printing (default: 1m0s) [$NTFY_MANAGER_INTERVAL]
   --smtp-sender-addr value                          SMTP server address (host:port) for outgoing emails [$NTFY_SMTP_SENDER_ADDR]
   --smtp-sender-user value                          SMTP user (if e-mail sending is enabled) [$NTFY_SMTP_SENDER_USER]
   --smtp-sender-pass value                          SMTP password (if e-mail sending is enabled) [$NTFY_SMTP_SENDER_PASS]
   --smtp-sender-from value                          SMTP sender address (if e-mail sending is enabled) [$NTFY_SMTP_SENDER_FROM]
   --smtp-server-listen value                        SMTP server address (ip:port) for incoming emails, e.g. :25 [$NTFY_SMTP_SERVER_LISTEN]
   --smtp-server-domain value                        SMTP domain for incoming e-mail, e.g. ntfy.sh [$NTFY_SMTP_SERVER_DOMAIN]
   --smtp-server-addr-prefix value                   SMTP email address prefix for topics to prevent spam (e.g. 'ntfy-') [$NTFY_SMTP_SERVER_ADDR_PREFIX]
   --global-topic-limit value, -T value              total number of topics allowed (default: 15000) [$NTFY_GLOBAL_TOPIC_LIMIT]
   --visitor-subscription-limit value                number of subscriptions per visitor (default: 30) [$NTFY_VISITOR_SUBSCRIPTION_LIMIT]
   --visitor-attachment-total-size-limit value       total storage limit used for attachments per visitor (default: "100M") [$NTFY_VISITOR_ATTACHMENT_TOTAL_SIZE_LIMIT]
   --visitor-attachment-daily-bandwidth-limit value  total daily attachment download/upload bandwidth limit per visitor (default: "500M") [$NTFY_VISITOR_ATTACHMENT_DAILY_BANDWIDTH_LIMIT]
   --visitor-request-limit-burst value               initial limit of requests per visitor (default: 60) [$NTFY_VISITOR_REQUEST_LIMIT_BURST]
   --visitor-request-limit-replenish value           interval at which burst limit is replenished (one per x) (default: 10s) [$NTFY_VISITOR_REQUEST_LIMIT_REPLENISH]
   --visitor-email-limit-burst value                 initial limit of e-mails per visitor (default: 16) [$NTFY_VISITOR_EMAIL_LIMIT_BURST]
   --visitor-email-limit-replenish value             interval at which burst limit is replenished (one per x) (default: 1h0m0s) [$NTFY_VISITOR_EMAIL_LIMIT_REPLENISH]
   --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)