Contributing to the Mozilla codebase

  • Revision slug: Introduction
  • Revision title: Contributing to the Mozilla codebase
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This page should guide you through the first steps of contributing to Mozilla. Welcome, we're delighted to see you :)

Need help?

The Mozilla community always welcomes newcomers to our midst. If you have any difficulties anywhere while joining us, you can ask questions in the #introduction chat room on irc.mozilla.org. If you're still having problems, please contact Kyle Huey at khuey@mozilla.com.

What skills do I need?

Mozilla is a large project and we are happy to receive contributors with very different skills.

  • If you know C++, for instance, you can contribute to the core layers of Firefox, Firefox OS and other Mozilla products.
  • If you know JavaScript or HTML/CSS, for instance, you can contribute to the front-end of Firefox, or to Gaia, the application layer of Firefox OS.
  • If you know Java, for instance, you can contribute to Firefox Mobile.
  • If you know Python, for instance, you can contribute to our web services, including Firefox Sync or Persona.
  • If you know Make, shell, Perl or Python, you can contribute to our build system.
  • If you know C, for instance, you can contribute to a number of low-level and third-party libraries that we use as part of the Mozilla codebase.
  • And there are also many ways to contribute to the Mozilla mission without programming. If you'd like to get involved in design, support, translation, testing, or other types of of contributions, see the Volunteer Opportunities page.

Perhaps you do not know programming yet but you want to start learning? That's great too, and the Webmaker program is for you!

Step 1 - Build Firefox, Thunderbird or another application

Follow our set of simple instructions to build Firefox, or to build Thunderbird. This is straightforward, but may take some time, so you may want to move on to the next steps while it builds.

More build instructions can be found here.

Step 2 - Understand how contributing to Mozilla works

See Mozilla Firefox: Development Process. Thunderbird operates a similar process.

Step 3 - Find something to work on

Fix your pet peeve

If there's something you'd like to fix about Firefox, Thunderbird or your other favourite Mozilla application, this can be a good place to start. There are a number of ways to do this:

Find a bug we've identified as being good for newcomers

Mozilla developers label certain bugs as being an easy bug to get newcomers acquainted with our processes:

  • Mentored bugs (or the alternative, less usable interface) have a mentor who commits to helping you every step of the way. Generally, there should be enough information in the bug to get started. Whenever you need help, contact the mentor over IRC, in the bug itself, or by email. When you've completed the bug, they will help you get your code into the tree.
  • "Good" first bugs may be a little stale, but at some point in their lives we considered that they would be a good first step for newcomers to Mozilla. We are in the process of migrating these bugs to mentored bugs, but more recent "good first bugs" may be good starting points if there are no appropriate mentored bugs.
  • Student projects are larger projects, such as might be suitable for a university student for credit. Of course, if you are not a student, you should still feel free to fix one of these bugs.

Step 4 - Fix the bug

We leave this in your capable hands. We have some resources to help you here too:

If the bug you're fixing is likely to require an update to developer documentation once it's fixed, be sure to add the dev-doc-needed keyword to the bug (or ask someone to do it, if you don't have editbugs privileges on Bugzilla). This puts the bug on the radar of our documentation team to ensure that once the bug is resolved, the documentation will be updated appropriately. If you don't mark the bug, your work might go unnoticed by the docs team! You can mark the bug with this keyword at any time; you don't need to wait until it's actually fixed.

Of course, our documentation is a wiki; you can really help by updating the documentation yourself. Even if you're not comfortable with your writing skills, keep in mind that our helpful, happy documentation gnomes will follow along behind you and clean up for you.

Step 5 - Get your code reviewed

Once you fix the bug, attach a patch to the bug, and ask for review. Do this by clicking the Details link on your attachment, then setting the review flag to ? and entering the reviewer's bugzilla ID in the text field that appears (either their email address of the :UniqueName they provide). It is very important to attach a bugzilla ID, or the request will be missed. So how do you figure out the right person to ask for a review?

  • If you have a mentored bug, ask your mentor, they will know or can find out easily.
  • Run hg blame and look at the people who have touched the function's you've worked on - they will be a good candidate.
  • The bug itself may contain a clear indication of the best person to ask for a review.
  • Are there related bugs on similar topics? In that case, the reviewer in those bugs might be a good choice.
  • We have an out of date list of modules which lists peers and owners for the module, some of whom will be a good reviewer. In the worst case, set the module owner as the reviewer, and ask them in the comment to pick someone better if they don't have time.

Step 5b - Follow it up

If you've asked for review, but the reviewer hasn't said anything for a few days, don't be afraid to ping them. Just add a comment to the bug saying 'review ping?', and another a few days later if they still haven't responded. If they don't respond after that, ask for help in #introduction or #developers.

Step 6 - Respond to the review

Often, a reviewer will ask for changes, perhaps minor, perhaps major. In either case, fix what the reviewer asks for; if you're unsure how, be sure to ask! Attach the new patch to the bug again, and ask for review again from the same reviewer. If they give you an r+ that means that your bug is accepted into the tree!

Step 7 - Actually get the code into the tree

Since you don't yet have the ability to push the code into the tree, you should ask somebody for help. If you have a mentor, ask them. If not, ask the reviewer. If the reviewer is too busy, mark that a commit is needed by adding the checkin-needed keyword. A friendly person should be along within a few days and push the code to the repository, and they will mark the bug as fixed.

Step 8 - Repeat

Congratulations, you've fixed your first bug. Now go back to step 3 and repeat. Now that you've got your first bug in, you should request level 1 access to the repository so that you can push to tryserver and get automated feedback about your changes on multiple platforms. After fixing a nontrivial number of bugs, you should request level 2/3 access (depending on the repository you're using) so that you can push your own code after it has been r+ed.

More information

We're in the process of improving information on this page for newcomers to the project. We'll be integrating some information from these pages soon, but until then you may find them interesting in their current form:

Revision Source

<p>This page should guide you through the first steps of contributing to Mozilla. Welcome, we're delighted to see you :)</p>
<h2 id="Need_help.3F">Need help?</h2>
<p>The Mozilla community always welcomes newcomers to our midst. If you have any difficulties anywhere while joining us, you can ask questions in the <a class="link-https" href="https://chat.mibbit.com/?url=irc%3A%2F%2Firc.mozilla.org%2F%23introduction">#introduction chat room on irc.mozilla.org</a>. If you're still having problems, please contact Kyle Huey at <a class="link-mailto" href="mailto:khuey@mozilla.com" rel="freelink">khuey@mozilla.com</a>.</p>
<h2 id="Not_C.2B.2B.3F">What skills do I need?</h2>
<p>Mozilla is a large project and we are happy to receive contributors with very different skills.</p>
<ul>
  <li>If you know C++, for instance, you can contribute to the core layers of Firefox, Firefox OS and other Mozilla products.</li>
  <li>If you know JavaScript or HTML/CSS, for instance, you can contribute to the front-end of Firefox, or to Gaia, the application layer of Firefox OS.</li>
  <li>If you know Java, for instance, you can contribute to Firefox Mobile.</li>
  <li>If you know Python, for instance, you can contribute to our web services, including Firefox Sync or Persona.</li>
  <li>If you know Make, shell, Perl or Python, you can contribute to our build system.</li>
  <li>If you know C, for instance, you can contribute to a number of low-level and third-party libraries that we use as part of the Mozilla codebase.</li>
  <li>And there are also many ways to contribute to the Mozilla mission without programming. If you'd like to get involved in design, support, translation, testing, or other types of of contributions, see the <a class="external link-https" href="https://www.mozilla.org/contribute/areas.html" title="https://www.mozilla.org/contribute/areas.html">Volunteer Opportunities page</a>.</li>
</ul>
<p>Perhaps you do not know programming yet but you want to start learning? That's great too, and <a href="https://webmaker.org" title="https://webmaker.org">the Webmaker program</a> is for you!</p>
<h2 id="Step_1_-_Build_Firefox.2C_Thunderbird_or_another_application">Step 1 - Build Firefox, Thunderbird or another application</h2>
<p>Follow our set of <a href="/en-US/docs/Simple_Firefox_build" title="Simple Firefox Build">simple instructions to build Firefox</a>, or to <a href="/en-US/docs/Simple_Thunderbird_build" title="Simple Thunderbird build">build Thunderbird</a>. This is straightforward, but may take some time, so you may want to move on to the next steps while it builds.</p>
<p>More build instructions can be <a href="/en-US/docs/Developer_Guide/Build_Instructions" title="Developer_Guide/Build_Instructions">found here</a>.</p>
<h2 id="Step_2_-_Understand_how_contributing_to_Mozilla_works">Step 2 - Understand how contributing to Mozilla works</h2>
<p>See <a class="external" href="http://mozilla.github.com/process-releases/draft/development_overview/" title="http://mozilla.github.com/process-releases/draft/development_overview/">Mozilla Firefox: Development Process</a>. Thunderbird operates a <a class="external" href="http://people.mozilla.org/~mbanner2/tbdevspecifics/" title="http://people.mozilla.org/~mbanner2/tbdevspecifics/">similar process</a>.</p>
<h2 id="Step_3_-_Find_something_to_work_on">Step 3 - Find something to work on</h2>
<h3 id="Fix_your_pet_peeve">Fix your pet peeve</h3>
<p>If there's something you'd like to fix about Firefox, Thunderbird or your other favourite Mozilla application, this can be a good place to start. There are a number of ways to do this:</p>
<ul>
  <li><a class="link-https" href="https://bugzilla.mozilla.org/query.cgi" title="https://bugzilla.mozilla.org/query.cgi">Search bugzilla</a> for relevant keywords,</li>
  <li>Figure out the <a class="link-https" href="https://bugzilla.mozilla.org/describecomponents.cgi" title="https://bugzilla.mozilla.org/describecomponents.cgi">bugzilla component</a> in which your pet peeve is implemented, using the components list. Browse that component on bugzilla for related bugs.</li>
  <li>Ask in <a class="link-https" href="https://chat.mibbit.com/?url=irc%3A%2F%2Firc.mozilla.org%2F%23introduction">#introduction</a> or <a class="link-https" href="https://chat.mibbit.com/?url=irc%3A%2F%2Firc.mozilla.org%2F%23developers">#developers</a> on irc.mozilla.org.</li>
</ul>
<h3 id="Find_a_bug_we've_identified_as_being_good_for_newcomers">Find a bug we've identified as being good for newcomers</h3>
<p>Mozilla developers label certain bugs as being an easy bug to get newcomers acquainted with our processes:</p>
<ul>
  <li><a class="external" href="http://www.joshmatthews.net/bugsahoy/" title="http://www.joshmatthews.net/bugsahoy/">Mentored bugs</a> (or the alternative, <a class="link-https" href="https://bugzil.la/sw:%5Bmentor=" title="https://bugzil.la/sw:%5Bmentor=">less usable interface</a>) have a mentor who commits to helping you every step of the way. Generally, there should be enough information in the bug to get started. Whenever you need help, contact the mentor over IRC, in the bug itself, or by email. When you've completed the bug, they will help you get your code into the tree.</li>
  <li><a class="link-https" href="https://bugzil.la/sw:%5Bgood%20first%20bug%5D" title="https://bugzil.la/sw:[good first bug]">"Good" first bugs</a> may be a little stale, but at some point in their lives we considered that they would be a good first step for newcomers to Mozilla. We are in the process of migrating these bugs to mentored bugs, but more recent "good first bugs" may be good starting points if there are no appropriate mentored bugs.</li>
  <li><a class="link-https" href="https://bugzil.la/kw:student-project" title="https://bugzil.la/kw:student-project">Student projects</a> are larger projects, such as might be suitable for a university student for credit. Of course, if you are not a student, you should still feel free to fix one of these bugs.</li>
</ul>
<h2 id="Step_4_-_Fix_the_bug">Step 4 - Fix the bug</h2>
<p>We leave this in your capable hands. We have some resources to help you here too:</p>
<ul>
  <li>Check out <a href="/en-US/docs/Developer_Guide" title="En/Developer_Guide">https://developer.mozilla.org/En/Developer_Guide</a>,</li>
  <li>Ask for help in a comment on the bug, or in <a class="link-https" href="https://chat.mibbit.com/?url=irc%3A%2F%2Firc.mozilla.org%2F%23introduction">#introduction</a> or <a class="link-https" href="https://chat.mibbit.com/?url=irc%3A%2F%2Firc.mozilla.org%2F%23developers">#developers</a>.</li>
</ul>
<p>If the bug you're fixing is likely to require an update to developer documentation once it's fixed, be sure to add the <code>dev-doc-needed</code> keyword to the bug (or ask someone to do it, if you don't have editbugs privileges on Bugzilla). This puts the bug on the radar of our documentation team to ensure that once the bug is resolved, the documentation will be updated appropriately. If you don't mark the bug, your work might go unnoticed by the docs team! You can mark the bug with this keyword at any time; you don't need to wait until it's actually fixed.</p>
<p>Of course, our documentation is a wiki; you can really help by updating the documentation yourself. Even if you're not comfortable with your writing skills, keep in mind that our helpful, happy documentation gnomes will follow along behind you and clean up for you.</p>
<h2 id="Step_5_-_Get_your_code_reviewed">Step 5 - Get your code reviewed</h2>
<p>Once you fix the bug, <a href="/en-US/docs/Developer_Guide/How_to_Submit_a_Patch" title="How to Submit a Patch">attach a patch to the bug</a>, and ask for review. Do this by clicking the <strong>Details</strong> link on your attachment, then setting the <strong>review</strong> flag to <strong>?</strong> and entering the reviewer's bugzilla ID in the text field that appears (either their email address of the :UniqueName they provide). It is very important to attach a bugzilla ID, or the request will be missed. So how do you figure out the right person to ask for a review?</p>
<ul>
  <li>If you have a mentored bug, ask your mentor, they will know or can find out easily.</li>
  <li>Run <code>hg blame</code> and look at the people who have touched the function's you've worked on - they will be a good candidate.</li>
  <li>The bug itself may contain a clear indication of the best person to ask for a review.</li>
  <li>Are there related bugs on similar topics? In that case, the reviewer in those bugs might be a good choice.</li>
  <li>We have an out of date <a class="link-https" href="https://wiki.mozilla.org/Modules">list of modules</a> which lists peers and owners for the module, some of whom will be a good reviewer. In the worst case, set the module owner as the reviewer, and ask them in the comment to pick someone better if they don't have time.</li>
</ul>
<h3 id="Step_5b_-_Follow_it_up">Step 5b - Follow it up</h3>
<p>If you've asked for review, but the reviewer hasn't said anything for a few days, don't be afraid to ping them. Just add a comment to the bug saying 'review ping?', and another a few days later if they still haven't responded. If they don't respond after that, ask for help in <a class="link-https" href="https://chat.mibbit.com/?url=irc%3A%2F%2Firc.mozilla.org%2F%23introduction">#introduction</a> or <a class="link-https" href="https://chat.mibbit.com/?url=irc%3A%2F%2Firc.mozilla.org%2F%23developers">#developers</a>.</p>
<h2 id="Step_6_-_Respond_to_the_review">Step 6 - Respond to the review</h2>
<p>Often, a reviewer will ask for changes, perhaps minor, perhaps major. In either case, fix what the reviewer asks for; if you're unsure how, be sure to ask! Attach the new patch to the bug again, and ask for review again from the same reviewer. If they give you an <strong>r+</strong> that means that your bug is accepted into the tree!</p>
<h2 id="Step_7_-_Actually_get_the_code_into_the_tree">Step 7 - Actually get the code into the tree</h2>
<p>Since you don't yet have the ability to push the code into the tree, you should ask somebody for help. If you have a mentor, ask them. If not, ask the reviewer. If the reviewer is too busy, mark that a commit is needed by adding the <em>checkin-needed</em> keyword. A friendly person should be along within a few days and push the code to the repository, and they will mark the bug as fixed.</p>
<h2 id="Step_8_-_Repeat">Step 8 - Repeat</h2>
<p>Congratulations, you've fixed your first bug. Now go back to step 3 and repeat. Now that you've got your first bug in, you should request level 1 access to the repository so that you can push to tryserver and get automated feedback about your changes on multiple platforms. After fixing a nontrivial number of bugs, you should request level 2/3 access (depending on the repository you're using) so that you can push your own code after it has been <strong>r+</strong>ed.</p>
<h2 id="More_information">More information</h2>
<p>We're in the process of improving information on this page for newcomers to the project. We'll be integrating some information from these pages soon, but until then you may find them interesting in their current form:</p>
<ul>
  <li><a class="external" href="http://www.joshmatthews.net/blog/2010/03/getting-involve-with-mozilla/">A guide to learning the mozilla codebase</a>.</li>
  <li><a class="link-https" href="https://wiki.mozilla.org/JavaScript:New_to_SpiderMonkey">A beginner's guide to SpiderMonkey, Mozilla's Javascript engine.</a></li>
  <li><a class="external" href="http://www.brianbondy.com/mozilla/cheatsheet/" title="http://www.brianbondy.com/mozilla/cheatsheet/">Mozilla platform development cheatsheet.</a></li>
</ul>
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