Errors

The client counts errors; it does not ship stack traces, DOM snapshots or whole URLs.

field	meaning
e	number of error events on the window
r	number of unhandledrejection events
f	number of failed resource loads (scripts, images, stylesheets)
m	the first error or rejection message, truncated to 120 characters

e, r and f are inside the session payload in ext1, alongside the vitals. There are no separate error beacons: the counts ride the next page view, tracked event or session summary.

What counts

• A window error event with a message increments e and, if m is still empty, stores the message.
• A resource that fails to load also fires an error event on the element, but without a message; that increments f instead.
• An unhandledrejection increments r. If the reason is an Error, its message is used; otherwise the reason is stringified.
• Only the first message is kept, and it is cut at 120 characters. Later errors only change the counters.

What is not collected

• No stack traces.
• No DOM or form values.
• No request bodies or response bodies.
• No user identifiers.

If the page throws before the client is loaded, nothing is recorded; load the tag as early as you can without blocking rendering.