Mobile Testing
Crash-free session rate
Also known as: crash-free sessions, crash-free users
Crash-free session rate is the percentage of app sessions that finish without a crash — the headline stability metric mobile teams gate releases on, reported by crash-reporting SDKs rather than by the test suite.
It is measured in production, not in CI: a crash-reporting SDK records each session and whether it ended in a crash, and the rate is crash-free sessions over total sessions for a release. A closely related variant, crash-free users, counts distinct users rather than sessions and is the kinder-looking of the two, since one user crashing repeatedly counts once.
The metric belongs beside test results rather than inside them. A suite can be entirely green and the release still be unshippable because a crash only reproduces on real hardware under real usage. Mobile release gates therefore tend to combine both signals — test pass rate and flakiness from CI, crash-free rate from the field — with a staged rollout in between so the field number can be observed before full exposure.
- Measured in production by a crash SDK, not by your test suite.
- Sessions vs users are different denominators — state which one a target refers to.
- Pairs with a staged rollout: ship to a slice, watch the rate, then widen.
Related terms
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Last reviewed September 10, 2026