Gemini server
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This page is also available at gemini://

twins requires a configuration file to operate. It is loaded from ~/.config/twins/config.yaml by default. You may specify a different location via the --config argument.

Configuration options


Address to listen for connections on in the format of interface:port.

Listen on localhost


Listen on all interfaces



Content types may be defined by file extension. When a type is not defined for the requested file extension, content type is detected automatically.


Hosts are defined by their hostname followed by one or more paths to serve.

Paths may be defined as fixed strings or regular expressions (starting with ^).

Paths are matched in the order they are defined.

Fixed string paths will match with and without a trailing slash.

When accessing a directory the file index.gemini or index.gmi is served.

When a host is defined with the name default, other hosts and paths will use those values as the default configuration. It is not currently possible to enable an attribute by default and then disable it for individual paths.


A certificate and private key must be specified.

localhost certificate

Use openssl generate a certificate for localhost.

openssl req -x509 -out localhost.crt -keyout localhost.key \
  -newkey rsa:2048 -nodes -sha256 \
  -subj '/CN=localhost' -extensions EXT -config <( \
   printf "[dn]\nCN=localhost\n[req]\ndistinguished_name = dn\n[EXT]\nsubjectAltName=DNS:localhost\nkeyUsage=digitalSignature\nextendedKeyUsage=serverAuth")

Domain certificate

Use certbot to get a certificate from Let's Encrypt for a domain.

certbot certonly --config-dir /home/www/certs \
  --work-dir /home/www/certs \  
  --logs-dir /home/www/certs \
  --webroot \
  -w /home/www/ \
  -d \

Provide the path to the certificate file at certs/live/$DOMAIN/fullchain.pem and the private key file at certs/live/$DOMAIN/privkey.pem to twins.


Pages are also available via HTTPS on the same port by default. Set this option to true to disable this feature.

Pages are converted automatically by gmitohtml.


The size of the response body is included in the media type header by default. Set this option to true to disable this feature.

See for more information.



One resource must be defined for each path.


Serve static files from specified root directory.


Serve output of system command.

When input is requested from the user, it is available as a pseudo-variable $USERINPUT which does not require surrounding quotes. It may be used as an argument to the command, otherwise user input is passed via standard input.


Forward requests to Gemini server at specified URL.

Use the pseudo-scheme gemini-insecure:// to disable certificate verification.


Redirect requests to specified path or URL.


Any number of attributes may be defined for a path.


Cache duration (in seconds). Set to 0 to disable caching entirely. This is an out-of-spec feature. See for more information.


Forward requests to FastCGI server at specified address or path.

A Root attribute must also be specified.

Connect via Unix socket:


Connect via TCP:


When enabled, hidden files and directories may be accessed. This attribute is disabled by default.


Request text input from user.


Specifies content language. This is sent to clients via the MIME type lang parameter.


When enabled, directories without an index file will serve a list of their contents. This attribute is disabled by default.


Path to log file. Requests are logged in Apache format, excluding IP address and query.


Request sensitive text input from the user. Text will not be shown as it is entered.

When enabled, symbolic links may be accessed. This attribute is disabled by default.


Content type is normally detected automatically. This attribute forces a specific content type for a path.

End-of-line indicator

The Gemini protocol requires \r\n (CRLF) as the end-of-line indicator. This convention is carried over from protocol specifications first written in the 1970s. This requirement is antithetic to the spirit of Gemini (to improve upon the Finger and Gopher protocols), increasing the complexity of client and server implementations unnecessarily.

In anticipation of an improvement to the Gemini specification, administrators may configure twins to send standard \n (LF) line endings by setting SaneEOL to true.

References: 1 2 3 4

Example config.yaml

# Address to listen on
listen: :1965

# Custom content types
  .json: application/json; charset=UTF-8

# Hosts and paths to serve
  default: # Default host configuration
    paths: # Default path attributes
        lang: en
        log: /srv/log/gemini.log
        symlinks: true # Follow symbolic links
    cert: /srv/
    key: /srv/
        path: ^/.*\.php$
        root: /home/geminirocks/public_html
        fastcgi: unix:///var/run/php.sock
        path: /files
        root: /home/geminirocks/files
        cache: 604800 # Cache for 1 week
        list: true # Enable directory listing
        path: ^/(help|info)$
        root: /home/geminirocks/docs/help
        path: ^/proxy-example$
        proxy: gemini://localhost:1966
        path: ^/cmd-example$
        command: uname -a
        cache: 0 # Do not cache
        path: /
        root: /home/geminirocks/public_html
    cert: /srv/
    key: /srv/
        path: /redir-path-example
        redirect: /other-resource
        path: /redir-url-example
        redirect: gemini://
        path: /
        root: /home/twins/public_html