Bugsnag

For mobile-specific crash reporting (iOS, Android, React Native, Flutter), Bugsnag has historically had an edge — it was purpose-built for mobile stability with better breadcrumb tracking, device context, and the stability score metric that product teams love. Sentry has significantly improved its mobile SDKs and now offers strong iOS and Android support with performance monitoring (launch time, slow renders). Sentry also has a more active community, better open-source/self-hosted option, and broader performance features. For pure mobile crash reporting, both are excellent — Bugsnag wins on mobile UX and stability metrics; Sentry wins on ecosystem breadth, price (free self-hosted), and full-stack coverage if you have backend services too.

Bugsnag's Lite plan is free: 7,500 error events per month, 1 user, basic error grouping, and 7-day retention. This is useful for personal projects and prototypes but limiting for production applications — even low-traffic apps can exceed 7,500 events quickly if multiple users hit errors. Team plan ($59/month) adds 25,000 events, 5 users, and 30-day retention. Business ($149/month) supports 50,000 events and 15 users. For comparison, Sentry's free tier allows 5,000 errors/month + 10,000 performance transactions with unlimited users — making Sentry more generous for small teams. Firebase Crashlytics is free with no event limits for mobile crash reporting.

Application stability monitoring tracks the percentage of user sessions or app launches that complete without encountering an error — the 'stability score.' Bugsnag popularized this metric: a stability score of 99.5% means 5 in 1,000 sessions hit an error. This frames reliability in business terms (user impact) rather than technical terms (error count). Stability monitoring differs from general error monitoring by focusing on trends over time, app version comparisons (did this release make stability worse?), and setting stability targets. When a new app version drops the stability score from 99.8% to 98.5%, that's a signal to investigate the release — even if raw error counts are low because the new version is on few devices yet.