Server Configuration

The Isso configuration file is an INI-style textfile. It reads integers, booleans, strings and lists. Here’s the default isso configuration: isso.cfg. A basic configuration from scratch looks like this:

 dbpath = /var/lib/isso/comments.db
 host = https://example.tld/
 listen = http://localhost:1234/

To use your configuration file with Isso, append -c /path/to/isso.cfg to the executable or run Isso with an environment variable:

(.venv) $ isso -c /path/to/isso.cfg
(.venv) $ env ISSO_SETTINGS=/path/to/isso.cfg$ isso

Sections covered in this document:


In this section, you configure most comment-related options such as database path, session key and hostname.

Here are the default values for this section:

dbpath = /tmp/comments.db
name =
host =
max-age = 15m
notify = stdout
log-file =
gravatar = false
gravatar-url ={}?d=identicon&s=55
latest-enabled = false

File location to the SQLite3 database, highly recommended to change this location to a non-temporary location!

Default: /tmp/comments.db


Required to dispatch multiple websites, not used otherwise.

Default: (empty)


Your website(s). If Isso is unable to connect to at least one site, you’ll get a warning during startup and comments are most likely non-functional.

You’ll need at least one host/website to run Isso. This is due to security reasons: Isso uses CORS to embed comments and to restrict comments only to your website, you have to “whitelist” your website(s).

I recommend the first value to be a non-SSL website that is used as fallback if Firefox users (and only those) supress their HTTP referer completely.

host =

Default: (empty)


Time range that allows users to edit/remove their own comments. See Appendum: Timedelta for valid values.

Default: 15m


Select notification backend(s) for new comments, separated by comma. Available backends:


Log to standard output. Default, if none selected. Note, this functionality is broken since a few releases.


Send notifications via SMTP on new comments with activation (if moderated) and deletion links.

Default: stdout


Allow users to request E-mail notifications for replies to their post.

It is highly recommended to also turn on moderation when enabling this setting, as Isso can otherwise be easily exploited for sending spam.

Default: false


Log console messages to file instead of standard out.

Default: (empty)


When set to true this will add the property “gravatar_image” containing the link to a gravatar image to every comment. If a comment does not contain an email address, gravatar will render a random icon. This is only true when using the default value for “gravatar-url” which contains the query string param d=identicon

Default: false


Url for gravatar images. The {} is where the email hash will be placed.



If true it will enable the /latest endpoint.

Default: false


Enable moderation queue and handling of comments still in moderation queue

enabled = false
approve-if-email-previously-approved = false
purge-after = 30d

Enable comment moderation queue. This option only affects new comments. Comments in moderation queue are not visible to other users until you activate them.

Default: false


Automatically approve comments by an email address if that address has had a comment approved within the last 6 months. No ownership verification is done on the entered email address. This means that if someone is able to guess correctly the email address used by a previously approved author, they will be able to have their new comment auto-approved.

Default: false


Remove unprocessed comments in moderation queue after given time.

Default: 30d


HTTP server configuration.

listen = http://localhost:8080
public-endpoint =
reload = false
profile = false
trusted-proxies =
samesite =

Interface to listen on. Isso supports TCP/IP and unix domain sockets:

; UNIX domain socket
listen = unix:///tmp/isso.sock
listen = http://localhost:1234/

When gevent is available, it is automatically used for http:// Currently, gevent can not handle http requests on unix domain socket (see #295 and #299 for details).

Does not apply for uWSGI.

Default: http://localhost:8080


Public URL that Isso is accessed from by end users. Should always be a http:// or https:// absolute address. If left blank, automatic detection is attempted. Normally only needs to be specified if different than the listen setting.

This URL must not end in a / slash, i.e. is forbidden but http://foo/bar:8080 is fine.

Default: (empty)

Changed in version 0.13: Trailing slash now forbidden.


Reload application, when the source code has changed. Useful for development. Only works with the internal webserver.

Default: false


Show 10 most time consuming function in Isso after each request. Do not use in production.

Default: false


An optional list of reverse proxies IPs behind which you have deployed your Isso web service (e.g. This allow for proper remote address resolution based on a X-Forwarded-For HTTP header, which is important for the mechanism forbiding several comment votes coming from the same subnet.

Default: (empty)


Override Set-Cookie header SameSite value. Needed for setups where isso is not hosted on the same domain, e.g. called from and hosted under By default, isso will set SameSite=None when served over https and SameSite=Lax when served over http (see MDM: SameSite and #682 for details).

Accepted values: None, Lax, Strict

Default: (empty)


Isso can notify you on new comments via SMTP. In the email notification, you also can moderate (=activate or delete) comments. Don’t forget to configure notify = smtp in the general section.

username =
password =
host = localhost
port = 587
security = starttls
to =
from =
timeout = 10

Self-explanatory, optional

Default: (empty)


self-explanatory (yes, plain text, create a dedicated account for notifications), optional.

Default: (empty)


SMTP server

Default: localhost


SMTP port

Default: 587


Use a secure connection to the server.

Accepted values: none, starttls, ssl

Default: starttls


Recipient address, e.g. your email address

Default: (empty)


Sender address, e.g. "Foo Bar" <isso@example.tld>

Default: (empty)


Specify a timeout in seconds for blocking operations like the connection attempt.

Default: 10


Enable basic spam protection features, e.g. rate-limit per IP address (/24 for IPv4, /48 for IPv6).

enabled = true
ratelimit = 2
direct-reply = 3
reply-to-self = false
require-author = false
require-email = false

Enable guard, recommended in production. Not useful for debugging purposes.

Default: true


Limit to N new comments per minute.

Default: 2


How many comments directly to the thread (prevent a simple while true; do curl …; done.

Default: 3


Allow commenters to reply to their own comments when they could still edit the comment. After the editing timeframe is gone, commenters can reply to their own comments anyways.

Default: false


Force commenters to enter a value into the author field. No validation is performed on the provided value.

Default: false


Force commenters to enter a value into the email field. No validation is performed on the provided value.

Default: false


Customize markup and sanitized HTML. Currently, only Markdown (via Misaka) is supported, but new languages are relatively easy to add. For a more detailed explanation, see Configure how comments are rendered.

options = strikethrough, superscript, autolink, fenced-code
flags =
allowed-elements =
allowed-attributes =

Misaka-specific Markdown extensions, all extension options can be used there, separated by comma, either by their name (fenced-code) or as EXT_FENCED_CODE.

Note: Use e.g. fenced-code (with a - dash) instead of fenced_code (underline) to refer to extension names.

For a more detailed explanation, see Markdown Configuration: Extensions

Default: strikethrough, superscript, autolink, fenced-code


Misaka-specific HTML rendering flags, all html rendering flags can be used here, separated by comma, either by their name (hard-wrap) or as e.g. HTML_HARD_WRAP.

For a more detailed explanation, see Configure how comments are rendered.

Default: (empty)

Added in version 0.12.4.


Additional HTML tags to allow in the generated output, comma-separated.

By default, only a, blockquote, br, code, del, em, h1, h2, h3, h4, h5, h6, hr, ins, li, ol, p, pre, strong, table, tbody, td, th, thead and ul are allowed.

For a more detailed explanation, see Configure how comments are rendered.


This option (together with allowed-attributes) is frequently misunderstood. Setting e.g. this list to only a, blockquote will mean that br, code, del, ... and all other default allowed tags are still allowed. You can only add additional elements here.

It is planned to change this behavior, see this issue.

Default: (empty)


Additional HTML attributes (independent from elements) to allow in the generated output, comma-separated.

By default, only align and href are allowed (same caveats as for allowed-elements above apply)

For a more detailed explanation, see Configure how comments are rendered.

Default: (empty)


To allow images in comments, you need to add allowed-elements = img and also allowed-attributes = src.


Customize used hash functions to hide the actual email addresses from commenters but still be able to generate an identicon.

salt = Eech7co8Ohloopo9Ol6baimi
algorithm = pbkdf2

A salt is used to protect against rainbow tables. Isso does not make use of pepper (yet). The default value has been in use since the release of Isso and generates the same identicons for same addresses across installations.

Default: Eech7co8Ohloopo9Ol6baimi


Hash algorithm to use – either from Python’s hashlib or PBKDF2 (a computational expensive hash function).

The actual identifier for PBKDF2 is pbkdf2:1000:6:sha1, which means 1000 iterations, 6 bytes to generate and SHA1 as pseudo-random family used for key strengthening. Arguments have to be in that order, but can be reduced to pbkdf2:4096 for example to override the iterations only.

Default: pbkdf2


Isso can provide an Atom feed for each comment thread. Users can use them to subscribe to comments and be notified of changes. Atom feeds are enabled as soon as there is a base URL defined in this section.

base =
limit = 100

Base URL to use to build complete URI to pages (by appending the URI from Isso)

Default: (empty)


number of most recent comments to return for a thread

Default: 100


Isso has an optional web administration interface that can be used to moderate comments. The interface is available under /admin on your isso URL.

enabled = true
password = please_choose_a_strong_password

Whether to enable the admin interface

Default: false


The plain text password to use for logging into the administration interface

Default: please_choose_a_strong_password



A human-friendly representation of a time range: 1m equals to 60 seconds. This works for years (y), weeks (w), days (d) and seconds (s), e.g. 30s equals 30 to seconds.

You can add different types: 1m30s equals to 90 seconds, 3h45m12s equals to 3 hours, 45 minutes and 12 seconds (12512 seconds).


Strings should not contain quotes, e.g. public-endpoint = is correct, = "" is wrong


For items that can be turned either on or off, acceptable values are (see getboolean):

  • For True, use 1, yes, true, or on

  • For False, use 0, no, false, or off