[Home](./index.md) > [puppeteer](./puppeteer.md) > [Protocol](./puppeteer.protocol.md) > [BackgroundService](./puppeteer.protocol.backgroundservice.md) > [EventMetadata](./puppeteer.protocol.backgroundservice.eventmetadata.md) > [key](./puppeteer.protocol.backgroundservice.eventmetadata.key.md) ## Protocol.BackgroundService.EventMetadata.key property Signature: ```typescript key: string; ```