Contributing to Apache Tomcat

Firstly, thanks for your interest in contributing! I hope that this will be a pleasant first experience for you, and that you will return to continue contributing.

Please visit our Get Involved page for more information on how to contribute.

Code of Conduct

This project and everyone participating in it is governed by the Apache software Foundation's Code of Conduct. By participating, you are expected to adhere to this code. If you are aware of unacceptable behavior, please visit the Reporting Guidelines page and follow the instructions there.

How Can I Contribute?

Most of the contributions that we receive are code contributions, but you can also contribute to the documentation, wiki, etc., or simply report solid bugs for us to fix.

Reporting Bugs

Please review our guide on how to submit a bug report. This page also has links to other resources to assist you.

Your First Code Contribution

Trouble Deciding How to Contribute?

Unsure where to begin contributing to Tomcat? You can start by taking a look at the issues marked ‘Beginner’, link below. Please note that the Beginner keyword is pretty new to the project, so if there aren't any issues in the filter feel free to ask on the dev list.

  • Beginner issues - issues which should only require a few lines of code, and a test or two to resolve.

The list above shows all bugs that are marked ‘Beginner’ and are open in the currently supported Tomcat versions (7, 8, and 9).

If you prefer C over Java, you may also take a look at the tomcat-native and Tomcat Connectors products in Bugzilla.

How to Provide Your First Patch

Excited yet? This section will guide you through providing a patch to the committers of the project for review and acceptance.

Chose Your Method of Submission

You can provide a patch in one of the following ways (in order of preference):

  • Patch attachment to the Bugzilla issue
  • Github Pull Request

Note: Github is a mirror of the SVN repository that Tomcat is stored in and therefore it can't be merged outright. Your contribution will be converted into an SVN patch and committed with a mention of your name for credit.

  • Email the patch to the developer list. This is not preferred, but if no bug is associated with the patch, or you would like a developer review, an email may be appropriate.
Get the Sources

Now that you've chosen how you want to submit a patch, you need to get the source code.

Download The Source Distribution

This method works if you want to submit a patch (like you would do for SVN), but the difference in using the sources distribution and a VCS is that you have to manually generate the patch file by using diff. If this is what you want, you can download the sources from the “Source Code Distributions” section of the Download Page.


If you have chosen to attach a patch to the Bugzilla issue (or email one), then you'll need to checkout the SVN version. Instructions for new committers to learn how to do this are found here. However, in the interest of a fast ramp up, the short version is below. Note that the root of the SVN repository is tomcat/trunk, but you can clone specific versions too, such as tc8.5.x or even tags ( TOMCAT_8_5_15).

$ svn co

For Github, it‘s almost the same. Chose the major version that you want (for now they’re in different repositories), fork the repository, and then clone your fork to do that work.

$ git clone$USERNAME/tomcat.git

Submitting Your Patch!

After you‘ve chosen your method of submission, retrieved the sources, and fixed the issue it’s time to submit your work. At this point, just follow the method of submission you chose earlier.

  • Bugzilla attachment - attach the SVN patch to the Bugzilla issue
  • Github PR - after resolving the issue in your local fork and pushing to your copy of the repository, open a Github PR for review.
  • Email - again, not preferred, but you may send an email to the developer list with a patch attached for review.

Waiting For Feedback

It may take a while for committers to review. Please be patient during this time as all committers are volunteers on the project. If a significant amount of time has lapsed since your submission, such as a couple of months, feel free to either update your BZ, PR, or email the dev list with a message to bump your issue. Sometimes things get lost in all the work and we need a reminder :smile:

Style Guide

Apache Tomcat has very loosely defined coding conventions, but the following guidelines will be useful:

  • Use spaces for indenting, not tabs
  • 100 char line width for Java source, 80 char line width for documentation source (.txt, .xml)
  • Java source: { at end of line, 4 space indents
  • XML source: 2 space indents

Did we miss something?

Have you reviewed this guide and found it lacking? Or are you confused about some particular step? If so, please let us know! Or better yet, submit a PR to address the issue :wink: