Error Monitoring for Builders
Console.log disappears the moment a tab closes. This course teaches you how to actually know when your production app breaks — capturing errors with full context, reading a stack trace through a minified bundle, setting up alerts that wake you up for the right things, and the triage workflow that turns a flood of errors into a manageable queue. By the end you will have a real error monitoring tool wired into a real app, catching a real bug.
What you'll learn
Course outline
Free — no account needed
Why Errors Need a Monitoring Tool
Your users do not file bug reports — they just leave
How Error Monitoring Tools Work
A small SDK, a global error handler, and a dashboard that groups the noise
Your First Error Capture
Install an SDK, throw a real error on purpose, and watch it land in a dashboard
Full course — $59 one-time
Choosing an Error Monitoring Tool
Sentry, Bugsnag, Rollbar, and the rest — what actually differs between them
Source Maps & Readable Stack Traces
Without this, your "detailed" error reports point at meaningless minified code
Alerting & Triage Workflow
A flood of error notifications trains everyone to ignore them — alert on the right things
Performance Monitoring & Session Replay
Beyond crashes — slow pages and silent failures that never throw an exception
The Production Error Monitoring Checklist
Source maps, sampling, PII scrubbing, and the details that turn noise into signal
Get the full course
8 lessons — from your first error capture to production-grade alerting, source maps, and triage.
About this course
Error monitoring tools capture uncaught exceptions and unhandled rejections in production, with the full stack trace, browser/OS context, and frequency that a plain log file never gives you. Learning error monitoring means understanding how SDKs hook into a language's global error handler, how identical errors get grouped into a single issue instead of flooding a dashboard, why source maps are required to read a minified production stack trace, and how to design an alerting and triage workflow that catches real regressions without training your team to ignore notifications.
This course is for developers shipping anything to production who currently find out about bugs from user complaints rather than a dashboard. After completing it you will be able to install and configure a real error monitoring tool (Sentry), set up source maps so stack traces are actually readable, choose between Sentry, Bugsnag, Rollbar, and self-hosted options, design alert rules that route by severity instead of one noisy firehose channel, and apply a production checklist covering sampling, PII scrubbing, and release tracking.
Frequently asked questions
Do I need error monitoring if I already have server logs?
Server logs typically only capture errors that happen on your server. Client-side JavaScript errors in a user's browser never reach your server logs at all — they disappear the moment the tab closes unless something is specifically capturing them. Error monitoring tools install a global error handler on both the client and server, so frontend and backend errors land in one place with full context, instead of being split across log files you may not even have access to.
Why does my stack trace show meaningless variable names like a, b, and t?
Production JavaScript is minified for performance, which shortens variable and function names and removes structure. Without uploading a source map — a file that maps the minified code back to your original source — your monitoring tool has no way to translate the stack trace back into readable file names and line numbers. Most bundlers can generate source maps automatically, and tools like Sentry have build plugins that upload them privately during your CI build.
How do I stop error monitoring from blowing through my free tier in one bad day?
Set a sample rate for performance traces and session replay rather than capturing 100% of everything — most teams sample 10-20% of sessions plus 100% of sessions that hit an error. For a known noisy error you cannot immediately fix, use the tool's rate limiting or fingerprinting rules so it stops consuming your event quota at full volume. Most providers also let you set a budget alert before you hit your plan's cap.
What is the difference between an error and a performance issue in monitoring tools?
An error is a thrown exception or unhandled rejection — code that broke. A performance issue is something that worked but was slow, like a page that took 8 seconds to load or an API call with a high p95 response time — these never throw an exception, so error capture alone misses them entirely. Most modern tools (Sentry, for example) bundle performance monitoring and session replay alongside error capture in the same product.
Is it safe to send user data to an error monitoring tool?
Only if you scrub it first. Most SDKs support a beforeSend hook that lets you strip emails, tokens, cookies, or form values out of the error payload before it leaves your app. Confirm this is configured — and test it by deliberately triggering an error with fake sensitive data in a form field and checking it does not appear in the dashboard — rather than assuming default settings are safe.