[Home](./index.md) > [puppeteer](./puppeteer.md) > [Protocol](./puppeteer.protocol.md) > [Tracing](./puppeteer.protocol.tracing.md) > [StartRequest](./puppeteer.protocol.tracing.startrequest.md) > [streamFormat](./puppeteer.protocol.tracing.startrequest.streamformat.md) ## Protocol.Tracing.StartRequest.streamFormat property Trace data format to use. This only applies when using `ReturnAsStream` transfer mode (defaults to `json`). Signature: ```typescript streamFormat?: StreamFormat; ```