puppeteer/docs/api/puppeteer.coverage.md

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---
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>
</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.
</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.
</td></tr>
</tbody></table>