I want to know why crash-free sessions and crash-free users look wrong for my browser extension even though I see errors in Sentry.

For browser extensions, Sentry's recommended setup does not automatically capture unhandled errors in the same way it does for a typical browser application. Instead, you capture errors manually, for example with scope.captureException.

These manually captured errors are considered handled. They appear in Issues, but they don't reduce your crash-free sessions or crash-free users percentages. Only crashes and other unhandled failures that end the session are counted when calculating those Release Health metrics.

For the recommended setup and configuration for browser extensions, see the shared environments / browser extensions guide. For more information about how crash-free sessions and users are calculated, see Release Health.