--- sidebar_label: Coverage --- # Coverage class The Coverage class provides methods to gather information about parts of JavaScript and CSS that were used by the page. #### Signature: ```typescript export declare class Coverage ``` ## Remarks To output coverage in a form consumable by [Istanbul](https://github.com/istanbuljs), see [puppeteer-to-istanbul](https://github.com/istanbuljs/puppeteer-to-istanbul). ## Example An example of using JavaScript and CSS coverage to get percentage of initially executed code: ```ts // Enable both JavaScript and CSS coverage await Promise.all([ page.coverage.startJSCoverage(), page.coverage.startCSSCoverage(), ]); // Navigate to page await page.goto('https://example.com'); // Disable both JavaScript and CSS coverage const [jsCoverage, cssCoverage] = await Promise.all([ page.coverage.stopJSCoverage(), page.coverage.stopCSSCoverage(), ]); let totalBytes = 0; let usedBytes = 0; const coverage = [...jsCoverage, ...cssCoverage]; for (const entry of coverage) { totalBytes += entry.text.length; for (const range of entry.ranges) usedBytes += range.end - range.start - 1; } console.log(`Bytes used: ${(usedBytes / totalBytes) * 100}%`); ``` ## Constructors <table><thead><tr><th> Constructor </th><th> Modifiers </th><th> Description </th></tr></thead> <tbody><tr><td> <span id="_constructor_">[(constructor)(client)](./puppeteer.coverage._constructor_.md)</span> </td><td> </td><td> Constructs a new instance of the `Coverage` class </td></tr> </tbody></table> ## Methods <table><thead><tr><th> Method </th><th> Modifiers </th><th> Description </th></tr></thead> <tbody><tr><td> <span id="startcsscoverage">[startCSSCoverage(options)](./puppeteer.coverage.startcsscoverage.md)</span> </td><td> </td><td> </td></tr> <tr><td> <span id="startjscoverage">[startJSCoverage(options)](./puppeteer.coverage.startjscoverage.md)</span> </td><td> </td><td> **Remarks:** Anonymous scripts are ones that don't have an associated url. These are scripts that are dynamically created on the page using `eval` or `new Function`. If `reportAnonymousScripts` is set to `true`, anonymous scripts URL will start with `debugger://VM` (unless a magic //\# sourceURL comment is present, in which case that will the be URL). </td></tr> <tr><td> <span id="stopcsscoverage">[stopCSSCoverage()](./puppeteer.coverage.stopcsscoverage.md)</span> </td><td> </td><td> Promise that resolves to the array of coverage reports for all stylesheets. **Remarks:** CSS Coverage doesn't include dynamically injected style tags without sourceURLs. </td></tr> <tr><td> <span id="stopjscoverage">[stopJSCoverage()](./puppeteer.coverage.stopjscoverage.md)</span> </td><td> </td><td> Promise that resolves to the array of coverage reports for all scripts. **Remarks:** JavaScript Coverage doesn't include anonymous scripts by default. However, scripts with sourceURLs are reported. </td></tr> </tbody></table>