🔁 Hot Reload vs Hot Restart in Flutter

Flutter provides two powerful tools to speed up development: Hot Reload and Hot Restart. They may sound similar, but they serve different purposes.

🔥 Hot Reload

What it does:

Injects updated code into the running Dart Virtual Machine (VM)

Preserves the app's state (like entered text or current screen)

Applies code changes instantly, mostly for UI and minor logic changes

Use Hot Reload When:

You change UI elements

You tweak styles, layouts, or animations

You edit functions inside a widget

Shortcut:

In VS Code: Ctrl + \ or click the "Hot Reload" button

In terminal: Type r

Example:

You change a button color from blue to green → Use Hot Reload

✅ Pros:

Very fast

Keeps the app’s current screen and state

❌ Limitations:

Doesn’t apply changes to global variables, constructors, or state initializations

May not fix deep bugs or structural changes

🔄 Hot Restart

What it does:

Rebuilds the entire app from scratch

Resets all app state (like logged-in user or form input)

Runs main() again and reinitializes everything

Use Hot Restart When:

You change the app’s initial state

You modify main(), constructors, or global variables

You want to fully reset the app without closing it

Shortcut:

In VS Code: Ctrl + Shift + \ or click the "Hot Restart" button

In terminal: Type R

Example:

You change the default home screen widget → Use Hot Restart

✅ Pros:

Picks up changes Hot Reload can’t

Useful for fixing bugs related to initialization

❌ Limitations:

Slower than Hot Reload

You lose app state (e.g., filled forms, navigation history)

🧠 Summary Table

Feature Hot Reload Hot Restart

🔄 App Rebuild No (only updates widgets) Yes (full app restart)

💾 State Kept ✅ Yes ❌ No

⚡ Speed Super fast Slower than reload

🧩 Use For UI tweaks, minor logic Initialization, full reset

✅ When to Use Each?

Situation Use

Changing widget styles or layout Hot Reload

App acting buggy after a logic change Hot Restart

Modified global variables or main() Hot Restart

Iterating on UI quickly Hot Reload

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