GUI

The easiest way to use mozregression (at least on Windows) is via the GUI. This youtube video by Pascal Chevrel describes how to install and use it:

Command line

The command-line version of mozregression is good for power users or those using Linux or MacOS X.

Let’s say you just found a bug in the current nightly build and you know that bug didn’t exist in the nightly from a few weeks ago. You want to find the regression range of this bug (the window of commits the bug was introduced in).

To find the range run the mozregression command on the command-line and give it a known “good” date with the good argument:

mozregression --good 2014-12-25

You can also specify the most distant known “bad” nightly date with the bad argument.

mozregression --good 2014-12-25 --bad 2015-01-07

This will guide you through a bisection, automatically downloading and opening nightly builds from various dates (on new, clean profiles) and asking you whether the bug exists in them. After doing this a few times you’ll get the regression range, something like this:

Pushlog: https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=636498d041b5&tochange=2a193b7f395c

Then mozregression will go on and do the same things with integration builds to get you the smallest possible window range.

There is plenty of options for mozregression. See

mozregression -h

To list them all. Have a look at the documentation section to learn more!