Recording format

Each recording is a folder of the project’s data files. Read them over MCP with readGadgetFiles. The files can be large: read one at a time.

data/recordings/<id>/
  recording.json     what the recording is (written last)
  rrweb/NNNN.json    the page, as rrweb events, in order
  network/NNNN.json  the page's requests, as HAR 1.2
  assets/NNNN.json   the page's images, fonts and stylesheets

NNNN counts up from 0000. To get all of one kind, concatenate its files’ arrays in order (for network/, each file’s log.entries).

recording.json

interface Recording {
  id: string;
  title: string;
  url: string;               // the page the recording started on ("" if unknown)
  startedAt: number;         // milliseconds since the epoch (UTC)
  endedAt: number;
  eventCount: number;        // rrweb events, all rrweb/ files together
  rrwebShardCount: number;   // how many rrweb/ files
  networkEntryCount: number; // requests, all network/ files together
  networkShardCount: number;
  assetCount: number;
  assetShardCount: number;
  createdAt: number;         // when it was saved
  source: string;            // the extension and its version
}

recording.json is written after all the other files, so if it is there, the recording is complete.

rrweb/NNNN.json

Arrays of rrweb events. Every event has a timestamp in milliseconds since the epoch.

type	Event
4 Meta	The page’s address (data.href). A new href means a new page.
2 FullSnapshot	The whole page as a tree of nodes (data.node), each with an id.
3 IncrementalSnapshot	A change after it. data.source: 0 DOM change, 2 mouse, 3 scroll, 5 input.

Time zero of a recording is the first event’s timestamp. Requests and pins (a pin’s atMs, MCP server) count from it.

network/NNNN.json

HAR 1.2 files, { "log": { "entries": [...] } }, with these additions to each entry:

interface HarEntryExtras {
  _atMs: number | null;    // milliseconds from time zero; null before the first rrweb event
  _resourceType: string;   // "XHR", "Fetch", "Document", "Script", "Image", …
  _error?: string;         // set for a failed request
}
// On request.postData and response.content, a body over the size limit has no text,
// and instead: _truncated: true

• request.postData.text is what the page sent. response.content.text is the body, for API calls, documents and event streams whose body is text.
• A body is at most 256 KiB, and all bodies in a recording at most 8 MiB; past that, _truncated.
• What’s redacted: Recording.

To find the requests around a pin, compare _atMs with the pin’s atMs.

assets/NNNN.json

type Asset =
  | { url: string; kind: "file"; type: string; data: string } // data: base64
  | { url: string; kind: "css"; css: string };

The page’s look as recorded; replays use these copies. A file is kept if it’s at most 4 MB and the recording’s assets stay under 60 MB; otherwise only its address is in the rrweb events.