Sentry

Sentry is an application monitoring platform focused on helping developers find, understand, and fix problems in code that is already running. When an error or crash happens, Sentry captures it with the stack trace, the local variables, the release and commit that introduced it, the affected users, breadcrumbs of what led up to it, and, on the web, a session replay showing exactly what the user did. Issues are grouped intelligently so a spike of one bug is one item to triage rather than thousands, with alerting into Slack and issue trackers and suspect-commit detection that points at the likely cause. Beyond errors, Sentry does performance monitoring and distributed tracing to surface slow transactions, database queries, and API calls, plus uptime checks, cron monitoring, logs, and profiling, and it has added AI features that summarize issues and propose fixes. It provides SDKs for essentially every major language and framework, and its core server is open source and self-hostable. Sentry is used by individual developers and large engineering teams across web, mobile, backend, and games. It offers a free tier with a monthly event quota and usage-based paid plans that scale with volume and retention.