Sentry.io - From error tracking to performance monitoring, developers can see what actually matters, solve quicker, and learn continuously about their applications - from the frontend to the backend.

TrackJS JavaScript Error Logging - JavaScript Error Monitoring from TrackJS gives you context about what's happening in your end-users' browsers.

Rollbar - Rollbar collects errors that happen in your application, notifies you, and analyzes them so you can debug and fix them. Ruby, Python, PHP, Node.js, JavaScript, and Flash libraries available.

Bugfender - Cloud logging for your apps, not only crashes matter

Raygun - Raygun gives developers meaningful insights into problems affecting their applications. Discover issues - Understand the problem - Fix things faster.

Bird Eats Bug - Saw a bug? Send an instant replay to engineers. It will come with console logs and everything. Developers will ❤️ you.