Caddyfile for Mastodon 3.x and 4.x that also maps @username@example.com -> @username@mastodon.example.com

Caddyfile

example.com {
  header /.well-known/host-meta Access-Control-Allow-Origin *
  respond /.well-known/host-meta `https://mastodon.example.com{uri}`
  @webfinger {
      path /.well-known/webfinger*
  }

  reverse_proxy @webfinger {
    to http://localhost:3000

    header_up X-Forwarded-Port 443
    header_up X-Forwarded-Proto https

    transport http {
      keepalive 5s
      keepalive_idle_conns 10
    }
  }
}

mastodon.example.com {
  @local {
    file
    not path /
  }
  @local_media {
    path_regexp /system/(.*)
  }
  @streaming {
    path /api/v1/streaming/*
  }
  @cache_control {
    path_regexp ^/(emoji|packs|/system/accounts/avatars|/system/media_attachments/files)
  }

  root * /var/www/mastodon/live/public

  log {
    output file /var/log/caddy/mastodon.log
  }

  encode zstd gzip

  handle_errors {
    rewrite 500.html
    file_server
  }

  header {
    Strict-Transport-Security "max-age=31536000"
  }
  header /sw.js Cache-Control "public, max-age=0"
  header @cache_control Cache-Control "public, max-age=31536000, immutable"

  handle @local {
    file_server
  }

  ## If you've been migrated media from local to object storage, this navigate old URL to new one.
  # redir @local_media https://yourobjectstorage.example.com/{http.regexp.1} permanent

  reverse_proxy @streaming {
    to http://localhost:4000

    transport http {
      keepalive 5s
      keepalive_idle_conns 10
    }
  }

  reverse_proxy  {
    to http://localhost:3000

    header_up X-Forwarded-Port 443
    header_up X-Forwarded-Proto https

    transport http {
      keepalive 5s
      keepalive_idle_conns 10
    }
  }
}