Rollbar

Sentry is the better default choice for most teams — it has a larger community, better open-source/self-hosted option (free for self-hosting), richer performance monitoring features (transaction tracing, profiling), and a broader ecosystem of integrations. Sentry has also expanded into performance monitoring beyond just error tracking. Rollbar is a strong choice if you prioritize the RQL query language for advanced error analysis, telemetry breadcrumbs, or specific version/deploy tracking features. Rollbar's person tracking (associating errors with specific user IDs) is also well-implemented. For teams on a budget wanting to self-host, Sentry wins clearly.

Rollbar's free plan allows 5,000 events/month, 1 user, 30-day retention, and 30+ language SDKs — useful for personal projects and small side projects. The Essentials plan charges per 1,000 events for up to 10 users with longer retention and more features. Advanced adds unlimited users, SSO, custom grouping, and enhanced security. The main limitation of the free tier is the 5,000 event/month cap — a medium-traffic web application can easily exceed this. Sentry's free tier is more generous (5,000 errors/month + 10,000 performance transactions) and includes team collaboration.

Error monitoring captures exceptions and crashes in your production applications in real-time and surfaces them to developers with actionable context: stack traces, affected code lines, browser/OS details, user information, and request parameters. Without error monitoring, you learn about bugs from user complaints after the fact. With tools like Rollbar or Sentry, you're alerted the moment an error occurs, can see its frequency and impact (how many users affected), and get the context needed to reproduce and fix it. Error monitoring is especially critical for JavaScript frontends (where browser errors are invisible to server logs) and for correlating error spikes with code deployments.