puppeteer/website/versioned_docs/version-10.0.0/puppeteer.coverage.md

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[Home](./index.md) &gt; [puppeteer](./puppeteer.md) &gt; [Coverage](./puppeteer.coverage.md)

## Coverage class

The Coverage class provides methods to gathers information about parts of JavaScript and CSS that were used by the page.

<b>Signature:</b>

```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:

```js
// 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

|  Constructor | Modifiers | Description |
|  --- | --- | --- |
|  [(constructor)(client)](./puppeteer.coverage._constructor_.md) |  | Constructs a new instance of the <code>Coverage</code> class |

## Methods

|  Method | Modifiers | Description |
|  --- | --- | --- |
|  [startCSSCoverage(options)](./puppeteer.coverage.startcsscoverage.md) |  |  |
|  [startJSCoverage(options)](./puppeteer.coverage.startjscoverage.md) |  |  |
|  [stopCSSCoverage()](./puppeteer.coverage.stopcsscoverage.md) |  |  |
|  [stopJSCoverage()](./puppeteer.coverage.stopjscoverage.md) |  |  |