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wtf is metro?

skevy/metro — explained in plain English

Analysis updated 2026-07-17 · repo last pushed 2019-03-21

★ 1JavaScriptAudience · developerComplexity · 2/5DormantSetup · easy

TL;DR

Metro is the JavaScript bundler that packages React Native app code into a format phones can run, with fast reloads while developing.

Mindmap

mindmap
  root((repo))
    What it does
      Bundles JS files
      Fast reload
      Watches for changes
    Tech stack
      JavaScript
      React Native
    Use cases
      Mobile app builds
      Large codebases
      Instant reload dev
    Audience
      Mobile developers
      Startup teams
    Notable
      Split from React Native
      Works with no config

Code map

Detail Auto

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filefunction / class

Why would anyone build with this?

REASON 1

Bundle a React Native app's JavaScript, dependencies, and assets so it can run on iOS or Android.

REASON 2

Get near-instant reloads while developing so you can see code changes on your phone immediately.

REASON 3

Scale a React Native project to thousands of files without slowing the bundler down.

REASON 4

Ship a mobile app using the default bundler that React Native projects use out of the box.

What's in the stack?

JavaScriptReact Native

How it stacks up

skevy/metro0xmukesh/docusaurus-tutoriala15n/andrewscheuermann
Stars111
LanguageJavaScriptJavaScriptJavaScript
Last pushed2019-03-212021-12-272015-01-11
MaintenanceDormantDormantDormant
Setup difficultyeasyeasymoderate
Complexity2/52/51/5
Audiencedeveloperdevelopergeneral

Figures from each repo's GitHub metadata at analysis time.

How do you spin it up?

Difficulty · easy Time to first run · 5min

Works out of the box as the default bundler for React Native, needing little to no configuration.

Yoink these prompts

Prompt 1
Explain why my React Native app is using Metro and what it's doing behind the scenes when I run the app.
Prompt 2
Help me speed up Metro's reload time for my React Native project.
Prompt 3
Show me how to configure Metro for a large React Native app with many files.
Prompt 4
Walk me through troubleshooting a Metro bundling error in my React Native project.

Frequently asked questions

wtf is metro?

Metro is the JavaScript bundler that packages React Native app code into a format phones can run, with fast reloads while developing.

What language is metro written in?

Mainly JavaScript. The stack also includes JavaScript, React Native.

Is metro actively maintained?

Dormant — no commits in 2+ years (last push 2019-03-21).

How hard is metro to set up?

Setup difficulty is rated easy, with roughly 5min to a first successful run.

Who is metro for?

Mainly developer.

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