<titledata-rh="true">Contributing | Puppeteer</title><metadata-rh="true"name="twitter:card"content="summary_large_image"><metadata-rh="true"property="og:url"content="https://pptr.dev/contributing"><metadata-rh="true"name="docusaurus_locale"content="en"><metadata-rh="true"name="docsearch:language"content="en"><metadata-rh="true"name="docusaurus_version"content="18.2.1"><metadata-rh="true"name="docusaurus_tag"content="docs-default-18.2.1"><metadata-rh="true"name="docsearch:version"content="18.2.1"><metadata-rh="true"name="docsearch:docusaurus_tag"content="docs-default-18.2.1"><metadata-rh="true"property="og:title"content="Contributing | Puppeteer"><metadata-rh="true"name="description"content="First of all, thank you for your interest in Puppeteer!"><metadata-rh="true"property="og:description"content="First of all, thank you for your interest in Puppeteer!"><linkdata-rh="true"rel="icon"href="/img/favicon.ico"><linkdata-rh="true"rel="canonical"href="https://pptr.dev/contributing"><linkdata-rh="true"rel="alternate"href="https://pptr.dev/contributing"hreflang="en"><linkdata-rh="true"rel="alternate"href="https://pptr.dev/contributing"hreflang="x-default"><linkrel="stylesheet"href="/assets/css/styles.121c39a6.css">
We'd love to accept your patches and contributions!</p><h2class="anchor anchorWithStickyNavbar_LWe7"id="contributor-license-agreement">Contributor License Agreement<aclass="hash-link"href="#contributor-license-agreement"title="Direct link to heading"></a></h2><p>Contributions to this project must be accompanied by a Contributor License
Agreement. You (or your employer) retain the copyright to your contribution,
this simply gives us permission to use and redistribute your contributions as
part of the project. Head over to <ahref="https://cla.developers.google.com/"target="_blank"rel="noopener noreferrer">https://cla.developers.google.com/</a> to see
your current agreements on file or to sign a new one.</p><p>You generally only need to submit a CLA once, so if you've already submitted one
(even if it was for a different project), you probably don't need to do it
used in production.</li><li><code>npm run build:test</code> - Builds Puppeteer, test runner, tests, and artifacts used in
production.</li></ul><h2class="anchor anchorWithStickyNavbar_LWe7"id="testing-puppeteer">Testing Puppeteer<aclass="hash-link"href="#testing-puppeteer"title="Direct link to heading"></a></h2><p>For browser testing, you can run</p><divclass="language-bash codeBlockContainer_Ckt0 theme-code-block"style="--prism-color:#393A34;--prism-background-color:#f6f8fa"><divclass="codeBlockContent_biex"><pretabindex="0"class="prism-code language-bash codeBlock_bY9V thin-scrollbar"><codeclass="codeBlockLines_e6Vv"><spanclass="token-line"style="color:#393A34"><spanclass="token function"style="color:#d73a49">npm</span><spanclass="token plain"> run build:test </span><spanclass="token operator"style="color:#393A34">&&</span><spanclass="token plain"></span><spanclass="token function"style="color:#d73a49">npm</span><spanclass="token plain"> run </span><spanclass="token builtin class-name">test</span><br></span></code></pre><divclass="buttonGroup__atx"><buttontype="button"aria-label="Copy code to clipboard"title="Copy"class="clean-btn"><spanclass="copyButtonIcons_eSgA"aria-hidden="true"><svgclass="copyButtonIcon_y97N"viewBox="0 0 24 24"><pathd="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svgclass="copyButtonSuccessIcon_LjdS"viewBox="0 0 24 24"><pathd="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>We also have other tests such as <code>test:types</code> that tests types and
(all prefixed with <code>test</code>).</p><p>Puppeteer is using a custom test runner on top of Mocha that consults
the <ahref="https://github.com/puppeteer/puppeteer/blob/main/test/TestExpectations.json"target="_blank"rel="noopener noreferrer">TestExpectations.json</a>
to see if a given test result is expected or not. See more info about the test runner in <ahref="https://github.com/puppeteer/puppeteer/tree/main/tools/mochaRunner"target="_blank"rel="noopener noreferrer"><code>tools/mochaRunner</code></a>.</p><h2class="anchor anchorWithStickyNavbar_LWe7"id="code-reviews">Code reviews<aclass="hash-link"href="#code-reviews"title="Direct link to heading"></a></h2><p>All submissions, including submissions by project members, require review. We
information on using pull requests.</p><h2class="anchor anchorWithStickyNavbar_LWe7"id="code-style">Code Style<aclass="hash-link"href="#code-style"title="Direct link to heading"></a></h2><p>Our coding style is fully defined in
manually by running:</p><divclass="language-bash codeBlockContainer_Ckt0 theme-code-block"style="--prism-color:#393A34;--prism-background-color:#f6f8fa"><divclass="codeBlockContent_biex"><pretabindex="0"class="prism-code language-bash codeBlock_bY9V thin-scrollbar"><codeclass="codeBlockLines_e6Vv"><spanclass="token-line"style="color:#393A34"><spanclass="token function"style="color:#d73a49">npm</span><spanclass="token plain"> run lint</span><br></span></code></pre><divclass="buttonGroup__atx"><buttontype="button"aria-label="Copy code to clipboard"title="Copy"class="clean-btn"><spanclass="copyButtonIcons_eSgA"aria-hidden="true"><svgclass="copyButtonIcon_y97N"viewBox="0 0 24 24"><pathd="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svgclass="copyButtonSuccessIcon_LjdS"viewBox="0 0 24 24"><pathd="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>If some errors are returned, you can attempt to fix them using:</p><divclass="language-bash codeBlockContainer_Ckt0 theme-code-block"style="--prism-color:#393A34;--prism-background-color:#f6f8fa"><divclass="codeBlockContent_biex"><pretabindex="0"class="prism-code language-bash codeBlock_bY9V thin-scrollbar"><codeclass="codeBlockLines_e6Vv"><spanclass="token-line"style="color:#393A34"><spanclass="token function"style="color:#d73a49">npm</span><spanclass="token plain"> run </span><spanclass="token function"style="color:#d73a49">format</span><br></span></code></pre><divclass="buttonGroup__atx"><buttontype="button"aria-label="Copy code to clipboard"title="Copy"class="clean-btn"><spanclass="copyButtonIcons_eSgA"aria-hidden="true"><svgclass="copyButtonIcon_y97N"viewBox="0 0 24 24"><pathd="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svgclass="copyButtonSuccessIcon_LjdS"viewBox="0 0 24 24"><pathd="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><h2class="anchor anchorWithStickyNavbar_LWe7"id="project-structure">Project structure<aclass="hash-link"href="#project-structure"title="Direct link to heading"></a></h2><p>The following is a description of the primary folders in Puppeteer:</p><ul><li><code>src</code> - contains the source code for Puppeteer.</li><li><code>test/src</code> - contains the source code for Puppeteer tests.</li><li><code>utils</code>/<code>scripts</code> - contains various scripts.</li><li><code>tools/testserver</code> - contains the source code for our test servers in testing.</li><li><code>tools/mochaRunner</code> - contains the source code for our test runner.</li><li><code>compat</code> - contains code separated by module import type. See <ahref="https://github.com/puppeteer/puppeteer/blob/main/compat/README.md"target="_blank"rel="noopener noreferrer"><code>compat/README.md</code></a> for details.</li><li><code>test-d</code> contains type tests using <ahref="https://github.com/SamVerschueren/tsd"target="_blank"rel="noopener noreferrer"><code>tsd</code></a>.</li><li><code>third_party</code> contains all dependencies that we vendor into the final build. See the <ahref="https://github.com/puppeteer/puppeteer/blob/main/third_party/README.md"target="_blank"rel="noopener noreferrer"><code>third_party/README.md</code></a> for details.</li></ul><h3class="anchor anchorWithStickyNavbar_LWe7"id="shipping-cjs-and-esm-bundles">Shipping CJS and ESM bundles<aclass="hash-link"href="#shipping-cjs-and-esm-bundles"title="Direct link to heading"></a></h3><p>Puppeteer ships both CommonJS and ES modules, therefore we maintain two <code>tsconfig</code> files for each project: <code>tsconfig.esm.json</code> and <code>tsconfig.cjs.json</code>. At build time we compile twice, once for CommonJS and once for ES modules.</p><p>We compile into the <code>lib</code> directory which is what we publish on the npm repository and it'
to reflect that. See more info about TestExpectations.json in <ahref="https://github.com/puppeteer/puppeteer/tree/main/tools/mochaRunner"target="_blank"rel="noopener noreferrer"><code>tools/mochaRunner</code></a>.</p><h2class="anchor anchorWithStickyNavbar_LWe7"id="api-coverage">API Coverage<aclass="hash-link"href="#api-coverage"title="Direct link to heading"></a></h2><p>Every public API method or event should be called at least once in tests. To ensure this, the main <code>test</code> command runs coverage during testing.</p><h2class="anchor anchorWithStickyNavbar_LWe7"id="debugging-puppeteer">Debugging Puppeteer<aclass="hash-link"href="#debugging-puppeteer"title="Direct link to heading"></a></h2><p>See <ahref="https://github.com/puppeteer/puppeteer/blob/main/README.md#debugging-tips"target="_blank"rel="noopener noreferrer">Debugging Tips</a> in the readme.</p><h1>For Project Maintainers</h1><h2class="anchor anchorWithStickyNavbar_LWe7"id="rolling-new-chromium-version">Rolling new Chromium version<aclass="hash-link"href="#rolling-new-chromium-version"title="Direct link to heading"></a></h2><p>The following steps are needed to update the Chromium version.</p><ol><li>Find a suitable Chromium revision
To do so, run <code>tools/check_availability.js -rd</code> to find the latest suitable <code>dev</code> Chromium revision (see <code>tools/check_availability.js -help</code> for more options).</li><li>Update <code>src/revisions.ts</code> with the found revision number.</li><li>Update <code>versions.js</code> with the new Chromium-to-Puppeteer version mapping and update <code>lastMaintainedChromiumVersion</code> with the latest stable Chrome version.</li><li>Run <code>npm run check:protocol-revision</code>.
If it fails, update <code>package.json</code> with the expected <code>devtools-protocol</code> version.</li><li>Run <code>npm run build && npm run build:test</code> and <code>npm install</code>.</li><li>Run <code>npm test</code> and ensure that all tests pass. If a test fails, <ahref="#bisecting-upstream-changes">bisect</a> the upstream cause of the failure, and either update the test expectations accordingly (if it was an intended change) or work around the changes in Puppeteer (if it’s not desirable to change Puppeteer’s observable behavior).</li><li>Commit and push your changes and open a pull request.
The commit message must contain the version in <code>Chromium <version> (<revision>)</code> format to ensure that <ahref="https://pptr.dev/"target="_blank"rel="noopener noreferrer">pptr.dev</a> can parse it correctly, e.g. <code>'feat(chromium): roll to Chromium 90.0.4427.0 (r856583)'</code>.</li></ol><h3class="anchor anchorWithStickyNavbar_LWe7"id="bisecting-upstream-changes">Bisecting upstream changes<aclass="hash-link"href="#bisecting-upstream-changes"title="Direct link to heading"></a></h3><p>Sometimes, performing a Chromium roll causes tests to fail. To figure out the cause, you need to bisect Chromium revisions to figure out the earliest possible revision that changed the behavior. The script in <code>tools/bisect.js</code> can be helpful here. Given a pattern for one or more unit tests, it will automatically bisect the current range:</p><divclass="language-sh codeBlockContainer_Ckt0 theme-code-block"style="--prism-color:#393A34;--prism-background-color:#f6f8fa"><divclass="codeBlockContent_biex"><pretabindex="0"class="prism-code language-sh codeBlock_bY9V thin-scrollbar"><codeclass="codeBlockLines_e6Vv"><spanclass="token-line"style="color:#393A34"><spanclass="token plain">node tools/bisect.js --good 686378 --bad 706915 script.js</span><br></span><spanclass="token-line"style="color:#393A34"><spanclass="token plain">node tools/bisect.js --unit-test Response.fromCache</span><br></span></code></pre><divclass="buttonGroup__atx"><buttontype="button"aria-label="Copy code to clipboard"title="Copy"class="clean-btn"><spanclass="copyButtonIcons_eSgA"aria-hidden="true"><svgclass="copyButtonIcon_y97N"viewBox="0 0 24 24"><pathd="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svgclass="copyButtonSuccessIcon_LjdS"viewBox="0 0 24 24"><pathd="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>By default, it will use the Chromium revision in <code>src/revisions.ts</code> from the <code>main</code> branch and from the working tree to determine the range to bisect.</p><h2class="anchor anchorWithStickyNavbar_LWe7"id="releasing-to-npm">Releasing to npm<aclass="hash-link"href="#releasing-to-npm"title="Direct link to heading"></a></h2><p>We use <ahref="https://github.com/googleapis/release-please"target="_blank"rel="noopener noreferrer">release-please</a> to automate releases. When a release should be done, check for the release PR in our <ahref="https://github.com/puppeteer/puppeteer/pulls"target="_blank"rel="noopener noreferrer">pull requests</a> and merge it.</p></div></article><navclass="pagination-nav docusaurus-mt-lg"aria-label="Docs pages navigation"><aclass="pagination-nav__link pagination-nav__link--prev"href="/troubleshooting"><divclass="pagination-nav__sublabel">Previous</div><divclass="pagination-nav__label">Troubleshooting</div></a><aclass="pagination-nav__link pagination-nav__link--next"href="/chromium-support"><divclass="pagination-nav__sublabel">Next</div><divclass="pagination-nav__label">Chromium Support</div></a></nav></div></div><divclass="col col--3"><divclass="tableOfContents_bqdL thin-scrollbar theme-doc-toc-desktop"><ulclass="table-of-contents table-of-contents__left-border"><li><ahref="#contributor-license-agreement"class="table-of-contents__link toc-highlight">Contributor License Agreement</a></li><li><ahref="#getting-code"class="table-of-contents__link toc-highlight">Getting Code</a></li><li><ahref="#building-puppeteer"class="table-of-contents__link toc-highlight">Building Puppeteer</a></li><li><ahref="#testing-puppeteer"class="table-of-contents__link toc-highlight">Testing Puppeteer</a></li><li><ahref="#code-reviews"class="table-of-contents__link toc-highlight">Code reviews</a></li><li><ahref="#code-style"class="table-of-contents__link toc-highlight">Code Style</a></li><li><ahref="#project-structure"class="table-of-contents__link toc-highlight">Project structure</a><ul><
