2022-07-05 13:41:43 +00:00
---
sidebar_label: Coverage
---
# 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:
```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
| 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 ) | | |
