Server Configuration

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.conf <>. 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/cfg to the executable or run Isso with an environment variable:

~> isso -c path/to/isso.cfg
~> 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/isso.db
name =
host =
max-age = 15m
notify = stdout
log-file =
file location to the SQLite3 database, highly recommended to change this location to a non-temporary location!
required to dispatch multiple websites, not used otherwise.

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

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.

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.

Do not forget to configure the client accordingly.

Log console messages to file instead of standard out.
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
Url for gravatar images. The “{}” is where the email hash will be placed. Defaults to “{}?d=identicon”


Enable moderation queue and handling of comments still in moderation queue

enabled = 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.
remove unprocessed comments in moderation queue after given time.


HTTP server configuration.

listen = http://localhost:8080
reload = off
profile = off

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.

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.
reload application, when the source code has changed. Useful for development. Only works with the internal webserver.
show 10 most time consuming function in Isso after each request. Do not use in production.


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
self-explanatory (yes, plain text, create a dedicated account for notifications), optional.
SMTP server
SMTP port
use a secure connection to the server, possible values: none, starttls or ssl. Note, that there is no easy way for Python 2.7 and 3.3 to implement certification validation and thus the connection is vulnerable to Man-in-the-Middle attacks. You should definitely use a dedicated SMTP account for Isso in that case.
recipient address, e.g. your email address
sender address, e.g. “Foo Bar” <isso@example.tld>
specify a timeout in seconds for blocking operations like the connection attempt.


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.
limit to N new comments per minute.
how many comments directly to the thread (prevent a simple while true; do curl …; done.

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.

Do not forget to configure the client.


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

Do not forget to configure the client accordingly.


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

Do not forget to configure the client.


Customize markup and sanitized HTML. Currently, only Markdown (via Misaka) is supported, but new languages are relatively easy to add.

options = strikethrough, superscript, autolink
allowed-elements =
allowed-attributes =
Misaka-specific Markdown extensions, all flags starting with EXT_ can be used there, separated by comma.
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.
Additional HTML attributes (independent from elements) to allow in the generated output, comma-separated. By default, only align and href are allowed.

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

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.


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)
number of most recent comments to return for a thread


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 = secret
whether to enable the admin interface
the plain text pasword to use for logging into the administration interface



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).

Environment variables

Isso also support configuration through some environment variables:

By default, isso will use the Host or else the Referrer HTTP header of the request to defines a CORS Access-Control-Allow-Origin HTTP header in the response. This environent variable allows you to define a broader fixed value, in order for example to share a single Isso instance among serveral of your subdomains : ISSO_CORS_ORIGIN=*.example.test