Two tools dominate post-deploy debugging: error tracking (Sentry, Bugsnag, Rollbar) and session replay (LogRocket, FullStory, Hotjar). Teams that buy them treat them as complementary, but they actually answer different questions.
Error tracking answers: what broke?
Error tracking captures uncaught exceptions and unhandled promise rejections, fingerprints them by stack trace, and shows you the top errors by frequency. It's the right tool when:
- You need to know what's breaking, in priority order, right now.
- You want to detect regressions ("this error appeared 30 minutes ago, after the v2.4 deploy").
- You want stack traces so an engineer can jump straight to the line.
Session replay answers: how did the user get there?
Session replay records the DOM state, every input, every interaction. It's the right tool when:
- A user reports a bug and you can't reproduce locally.
- You need to understand a UX problem (where do users abandon? what do they click that they shouldn't?).
- You want to see the steps before a crash, not just the crash itself.
The combination is the unlock
Error tracking alone tells you a TypeError happened in the checkout flow. Session replay alone shows you a user struggling with a checkout. Combined: you click the TypeError, watch the exact 30 seconds before it crashed, and immediately see that the user had pasted text with an emoji that the validation regex didn't anticipate. The fix takes 3 minutes instead of 3 hours.
That's why the two tools are almost always bought together. The question is whether you buy them as separate products (Sentry + LogRocket = ~$120/mo for a small team) or as a single unified product (Nevision Pro = $39/mo, both included).
When you only need one
If you're a marketing team optimizing landing-page conversion, you don't need error tracking — you need heatmaps and funnels (Hotjar, Microsoft Clarity). If you're a backend-only API with no browser surface, you don't need session replay — you need error tracking and logs. Most product teams need both.