By now, we’ve built slices, dispatched actions, and even fetched data from APIs using createAsyncThunk. But as your app grows, debugging becomes more and more important.

This is where Redux DevTools comes in — a powerful debugging tool that lets you see inside your Redux store in real time.

In this lesson, we’ll learn how to:

• Use Time-Travel Debugging
• Inspect actions and state changes step-by-step
• Debug issues like API errors and infinite re-renders

🔎 What is Redux DevTools?

Redux DevTools is a browser extension that helps you:

• See every action that gets dispatched
• Inspect how the state changes after each action
• Jump backward and forward through state history (time-travel)

Install It:

Chrome: https://chrome.google.com/webstore/detail/redux-devtools Firefox: https://addons.mozilla.org/en-US/firefox/addon/reduxdevtools/

Once installed, open your browser dev tools → you’ll see a Redux tab.

🕰 Time-Travel Debugging

Time-travel debugging allows you to go back to previous states to understand how they changed.

For example:

1. Click + three times on the counter app

2. You’ll see actions:

   • increment
   • increment
   • increment

3. Click on each action in the DevTools panel

4. The UI will update to show what the app looked like at that moment

This is extremely helpful for:

• Testing user flows
• Tracking UI bugs
• Understanding unexpected state changes

🔍 Inspecting Actions & State Changes

Every time you dispatch an action, Redux DevTools logs:

For example, when fetching Pokémon:

fetchPokemon/pending
fetchPokemon/fulfilled

You can inspect how status, items, and error changed at each step.

This makes debugging super clear.

🐞 Debugging Common Issues

1. API Not Working → Check Action Sequence

If the fetch fails, DevTools will show:

fetchPokemon/rejected

Click it → check error state → now you know what went wrong (e.g., wrong URL, CORS issue, API offline)

2. Infinite Re-Render Loop

If your component keeps re-rendering repeatedly:

• Check if you’re calling dispatch() inside render instead of useEffect.

❌ BAD:

dispatch(fetchPokemon());

✅ GOOD:

useEffect(() => {
  dispatch(fetchPokemon());
}, [dispatch]);

DevTools can show you hundreds of repeated actions → this is a red flag.

3. State Not Updating

If the UI doesn’t reflect assigned updates:

• Check your reducer logic in the slice
• Ensure you’re modifying the correct value
• Look at the Diff panel to confirm the state changed

🎯 Summary

Redux DevTools helps you:

Learning how to debug is just as important as learning how to code. Debug faster → Learn faster → Build better.

🚀 Next Lesson (Video 9): Performance Optimization with Selectors

In the next video, we’ll learn about:

• Memoized selectors with Reselect
• Preventing unnecessary re-renders
• Structuring slices efficiently

This will make your Redux app faster and smoother, especially as it grows.

If you’d like, I can now create:

✅ A YouTube narration script ✅ Visual slide images you can show in the video ✅ Thumbnail text ideas

Just tell me: Should your video tone be:

1. Beginner-friendly
2. Energetic YouTuber vibe
3. Serious / professional instructional style

Reply with 1, 2, or 3.