[Home](./index.md) > [puppeteer](./puppeteer.md) > [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.
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:
```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 Coverage 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) | | |