Sentry captures exceptions and performance data from applications in production. When something breaks, you get a stack trace, the context around the error, and information about how many users were affected. It supports most languages and frameworks, including JavaScript, Python, Ruby, Java, Go, and PHP. Issues are grouped so the same error does not flood your dashboard.

It integrates with GitHub, GitLab, Slack, and Jira, so you can create tickets or notify channels directly from an error. The free tier covers small projects, with paid plans scaling by event volume. For teams that want to know about errors before users complain, it is one of the most widely used tools in the category.