What is hotreload?

Hot reload is a development feature that lets you change your code and see the results instantly in a running app, without having to stop the app, rebuild it, and start it again. The app’s state (like what screen you’re on or the data you’ve entered) stays the same while the new code is injected and applied.

Let's break it down

  • Write code - You edit a file (e.g., a UI component or a function).
  • Save - The development tool detects the change.
  • Inject - The new code is sent to the running app.
  • Update - The app replaces the old logic with the new one while keeping the current state alive.
  • See instantly - The screen updates right away, so you can verify the change immediately.

Why does it matter?

Hot reload speeds up the feedback loop for developers. Instead of waiting minutes for a full rebuild, you get results in seconds. This makes experimenting, debugging, and polishing UI/UX much faster, leading to higher productivity and fewer “it works on my machine” problems.

Where is it used?

  • Mobile frameworks: Flutter, React Native, Xamarin.
  • Web development: Vite, Snowpack, Next.js (fast refresh).
  • Desktop UI toolkits: Electron with hot module replacement, .NET MAUI.
  • Game engines: Unity’s Play Mode with script recompilation, Unreal Engine’s hot reload for C++ modules.
  • Server‑side: Node.js with nodemon or ts-node-dev, Django’s auto‑reload for development servers.

Good things about it

  • Speed - Immediate visual feedback cuts development time.
  • State preservation - Keeps the app’s current data, so you don’t have to navigate back to the same screen after each change.
  • Encourages experimentation - You can try ideas quickly without fear of long rebuilds.
  • Better debugging - Spot errors right after the change, making it easier to isolate problems.
  • Consistent workflow - Works the same across many platforms, so developers learn one pattern and apply it everywhere.

Not-so-good things

  • Limited to certain changes - Deep structural changes (e.g., adding new files, changing class hierarchies) may still require a full restart.
  • Potential for stale state - If the new code expects a different state shape, the app can behave oddly until you do a full reload.
  • Memory leaks - Repeated hot reloads can sometimes leave behind objects that aren’t cleaned up, leading to increased memory usage during a long session.
  • Debugging complexity - The hot‑reloaded code runs in a slightly different environment, which can hide issues that only appear after a full restart.
  • Tooling dependence - Not all libraries or frameworks support hot reload equally; some may need extra configuration.