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From the Expo website

Expo lets web developers build truly native apps that work across both iOS and Android by writing them once in just JavaScript.

Isn't this what React Native does? What's the difference?

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When you write code in Expo you are writing React Native code. Expo has two main pieces:

  1. Expo CLI (expo-cli): a developer tool for creating projects, viewing logs, opening on your device, publishing, etc.

  2. Expo client: an app on your phone that lets you open your projects while you're working on them, without needing to go through XCode or Android Studio, and also lets other people view them too! And if you publish it through expo-cli, people can access it at any time through the Expo client on Android or on iOS if signed in to the same account it was published with. Lastly, we also make it possible to build standalone apps so people don't have to use the Expo client to open it, and you can distribute to the app store and play store if you like.

So Expo is a set of tools built on top of React Native. These tools depend on one key belief held at Expo: it's possible to build most apps without ever needing to write native code, provided that you have a comprehensive set of APIs exposed to JavaScript.

This is important because with React Native you can always drop down to native code. This is incredibly helpful sometimes but it comes at a cost: you need to send people your binaries if you want them to test them, someone on the other side of the world can't just tap a link to open it while you're working on it and you can't just publish it with one click for someone to access it similar to how you would in a browser.

With Expo, we suggest that try to avoid dropping down to native code, if you can. As I mentioned above, we think that with a comprehensive set of APIs available to JavaScript, this shouldn't be necessary for most apps. So, we aim to provide this comprehensive set of APIs, and then build all of the awesome tooling that can exist in a world where the native runtime is shared.

However, if you must find that you want to drop down to native, you can use eject and continue using the native APIs that Expo gives you while having the same level of control as you would in any native project.

Read more about ejecting

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    "With Exponent, you cannot drop down to native code". It's nice to know that you don't HAVE to drop down to native code, but what about if you need to, why would Exponent prevent you from doing it?
    – Otto
    Commented Aug 28, 2016 at 5:04
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    Ah I can see how that was unclear. So the Exponent client is completely open source (github.com/exponentjs/exponent) which means you can write native code if you like, but then you effectively are just treating the Exponent libraries as a collection of native modules in an otherwise typical React Native app. This is totally fine and was a motivator for us to open source the project. That said, if you want to be able to use our tooling (app binary builder, Exponent client on the app/play store to share test builds, built-in push notifications, etc.) then you can't write native code.
    – brentvatne
    Commented Aug 28, 2016 at 6:15
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    at the time of writing, Expo has gotten pretty good with integrating useful native plugins. However, they're lacking a MAJOR plugin integration for IAP and without it, you can't make money off of you app!!! And you ask, what's the point of making an app if I can't make profit!!
    – Adam
    Commented Jan 22, 2020 at 18:18
  • ExpoLink is now deprecated/will be deprecated soon, to be replaced by Expo Bare Workflow
    – bzr
    Commented Nov 19, 2020 at 21:05
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    I couldn't find a clear write-up of how the Expo build and push notification services work, but it appears that if you go with Expo you will be dependent their cloud-based build system and can only receive push notifications through their backend. I don't know what other services Expo apps depend on; I'm hoping someone else can explain it in more detail.
    – Sean O'Dell
    Commented Jan 17, 2021 at 21:20
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A summary of the documentation and answers from Expo employees:

React Native init:

Advantages

  • You can add native modules written in Java or Objective-C (probably the only but the strongest one)

Disadvantages

  • Needs Android Studio and Xcode to run the projects
  • You can't develop for iOS without having a Mac
  • Device has to be connected via USB to use it for testing
  • Fonts need to be imported manually in Xcode
  • If you want to share the app you need to send the whole .apk / .ipa file
  • Does not provide JavaScript APIs out of the box, e.g., Push-Notifications, Asset Manager, they need to be manually installed and linked with npm for example
  • Setting up a working project properly (including device configuration) is rather complicated and can take time

Expo

Advantages

  • Setting up a project is easy and can be done in minutes
  • You (and other people) can open the project while you're working on it
  • Sharing the app is easy (via a QR code or link), you don't have to send the whole .apk or .ipa file
  • No build necessary to run the app
  • Integrates some basic libraries in a standard project (Push Notifications, Asset Manager, etc.)
  • You can eject it to ExpoKit and integrate native code continuing using some of the Expo features, but not all of them
  • Expo can build .apk and .ipa files (distribution to stores possible with Expo)

Disadvantages

  • You can't add native modules (probably a game changer for some)
  • You can't use libraries that use native code in Objective-C/Java
  • The standard Hello World app is about 25MB big (because of the integrated libraries)
  • If you want to use: FaceDetector, ARKit, or Payments you need to eject it to ExpoKit
  • Ejecting it to ExpoKit has a trade-off of features of Expo, e.g. you cannot share via a QR code
  • When ejecting to ExpoKit you are limited to the react-native version that is supported by ExpoKit then
  • Debugging in ExpoKit (with native modules) is a lot more complicated, since it mixes two languages and different libraries (no official Expo support any more)

Sources:

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    Thank you @BenjaminHeinke for a clear picture of advantages and disadvantages. I am already experiencing disadvantage#2 with our decision to adopt expo for out react native app. We cannot integrate with Appsee because of this. Is there no workaround for this?
    – CoolDocMan
    Commented Jul 3, 2018 at 11:00
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    Device does not have to be connected to USB for tests, only the first compilation and install have to be done over USB. Later you can use Wi-Fi! Will need a recompilation if you make changes to native though.
    – rszalski
    Commented Nov 1, 2018 at 21:38
  • This should've been the accepted answer. It explains the differences, advantages and trade-offs really well
    – Miguel Jara
    Commented Oct 24, 2022 at 19:03
  • Just for reference, the expectation that you don't/won't need an iOS device or Mac to at least test your code is not a great one to have. I ended up needing a Mac with xcode (which also means latest mac OS must be installed) to run iOS simulator, simply because lots of CSS that works on web/android doesn't work with iOS, or even shows different results (though it mostly just crashes).
    – user8112809
    Commented Nov 15, 2022 at 18:35
  • Actually, you can add native modules in Expo by making use of their dev-client. You will then use EAS to build your dev-client to replace Expo Go which then can have whatever native modules you want added to it.
    – BruceHill
    Commented Mar 20 at 11:35
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The answer of Brent Vatne is fine, but I'd like to add some details.

Expo expands the API surface of React Native

React Native does not give you all the JavaScript APIs you need out of the box, but only most primitive features. React Native developers are expected to use Android Studio or Xcode to link additional native libraries.

Expo aims to enhance React Native and provide all the JavaScript APIs you need for the most common needs. It is basically a set of well-defined quality native libs already packaged for you in a single lib: ExpoKit. Sometimes these libraries are actually already existing in the React Native world, and integrated into ExpoKit.

It is also important to notice that the Expo team can't include every library out there into ExpoKit (which may create some frustration) because the Hello, World! app size would grow, as it would ship a lot of API's that wouldn't be used in most apps.

Expo provides over-the-air JavaScript updates

Like other systems (CodePush, etc.), Expo provides a system to update your app over the air. This means you upload your JavaScript bundle on a CDN and the mobile apps will automatically download and use the new JavaScript code on next startup (without requesting a publication/review from the stores).

Expo provides a CLI tool to upload/manage the JavaScript bundles on their CDN. For development you can also choose to become the CDN and host the JavaScript bundle on localhost. And Expo XDE is just a visual wrapper on the CLI.

Expo provides a generic client

The Expo client is a generic client that permits to load any app that is compatible with Expo. All the Expo apps do share the exact same native runtime (React Native + ExpoKit). The only difference is the JavaScript code that we give them. The Expo apps you publish to the app stores have your JavaScript bundle URL hardcoded in it. The Expo client is build in a specific way so that you can choose from which URL to load the JS, by scanning a QR code or providing a URL.

Note that this client can also load JavaScript bundles from localhost, and make your development experience easier: There isn't any need for Xcode or Android Studio, and it gets much faster to get your first Hello, World! app running on the phone (from hours to minutes). You can actually develop on an iPhone without a Mac and the setup takes two minutes.

Actually, as the Expo SDK can be upgraded, the Expo client includes a compatibility layer so that it is able to run the last five SDK versions.

Expo provides a build service

As all the Expo apps share the same native code, Expo is able to easily build these apps for you. They have created a cloud build service.

The major thing that differentiate two apps built by Expo is just the hardcoded URL to which the app is supposed to download the JavaScript bundle to run.

Expo does some other things for you, like providing a declarative way to setup app icons, orientations, permissions, API keys, helping you setup push notifications, provisioning profiles... many settings have to be hardcoded at build time in the app and can't be changed over the air.

Expo is to React Native what PhoneGap is to Cordova

React Native is similar Cordova. It is not the same view technology (native vs webview), but both allow you to control native features from JavaScript, and both offer a plugin system so that developers can easily add new JavaScript and native bindings.

PhoneGap is similar to Expo. They both try to enrich the raw API of the underlying platform they are built on with a predefined set of additional native plugins. PhoneGap also offers a build service and has a generic client that work as long as you use the approved plugins.

Conclusion

As you can see, Expo is a set of tools. At the end, it permits to easily develop, share and publish to the stores your mobile projects. It is quite similar to the PhoneGap experience (but a lot better and less confusing).

I will definitively recommend Expo for any new React Native greenfield project, except these two cases:

  • You already know you need API's that are not available in Expo and won't be anytime soon
  • You care a lot about your app size (Hello, World! is more than 25 MB due to the large size of ExpoKit, but after that it does not increase much as it is just JavaScript)
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    I'm trying to find a list of API's Expo does not support. Anyone knows where to find this?
    – ronnyrr
    Commented Mar 9, 2018 at 9:24
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    @ronnyrr I think this is what you’re looking for: expo.canny.io it’s a list of feature requests that you can sort by popularity
    – Evan Bacon
    Commented Jun 10, 2018 at 23:08
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It is explained in the official Expo documentation

What is the difference between Expo and React Native?

Expo is kind of like Rails for React Native. Lots of things are set up for you, so it’s quicker to get started and on the right path.

With Expo, you don’t need Xcode or Android Studio. You just write JavaScript using whatever text editor you are comfortable with (Atom, vim, emacs, Sublime, VS Code, whatever you like). You can run XDE (our desktop software) on Mac, Windows, and Linux.

Here are some of the things Expo gives you out of the box that work right away:

Support for iOS and Android

You can use apps written in Expo on both iOS and Android right out of the box. You don’t need to go through a separate build process for each one. Just open any Expo app in the Expo Client app from the App Store on either iOS or Android (or in a simulator or emulator on your computer).

Push Notifications

Push notifications work right out of the box across both iOS and Android, using a single, unified API. You don’t have to set up APNS and GCM/FCM or configure ZeroPush or anything like that. We think we’ve made this as easy as it can be right now.

Facebook Login

This can take a long time to get set up properly yourself, but you should be able to get it working in 10 minutes or less on Expo.

Instant Updating

All Expo apps can be updated in seconds by just clicking Publish in XDE. You don’t have to set anything up; it just works this way. If you aren’t using Expo, you’d either use Microsoft Code Push or roll your own solution for this problem

Asset Management

Images, videos, fonts, etc. are all distributed dynamically over the Internet with Expo. This means they work with instant updating and can be changed on the fly. The asset management system built-in to Expo takes care of uploading all the assets in your repo to a CDN so they’ll load quickly for anyone.

Without Expo, the normal thing to do is to bundle your assets into your app which means you can’t change them. Or you’d have to manage putting your assets on a CDN or similar yourself.

Easier Updating To New React Native Releases

We do new releases of Expo every few weeks. You can stay on an old version of React Native if you like, or upgrade to a new one, without worrying about rebuilding your app binary. You can worry about upgrading the JavaScript on your own time.

But no native modules…

The most limiting thing about Expo is that you can’t add in your own native modules without detaching and using ExpoKit.

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Expo CLI

Pros:

  1. No need to install Android Studio or Xcode to start building.
  2. Not a lot of configuration required.
  3. Mobile UI to easily view on both Android and iPhone using barcode scanning. Also easier to view with online iPhone and Android simulators.
  4. Faster setup and development.

Cons:

  1. Native dependencies cannot be added.
  2. Creating .apk and .ipa files is difficult.
  3. Size of apk/ipa is huge.

React Native CLI

Pros:

  1. Easily add native dependencies.
  2. Creating .apk and .ipa files is much easier than with Expo

Note: React Native CLI is the framework to use to work directly with the React Native framework.

Cons:

  1. High level of configuration required.
  2. Basic knowledge of Android and iOS folder structure required.

As you can see, both approaches have their pros and cons; you should always decide which to use based on your needs for the project.

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  • Concise and to-the-point explanation. Thanks!
    – Arundale Ramanathan
    Commented Jul 18, 2021 at 16:36
  • (At first glance it looks like plagiarism, but it isn't—user Sampson Crowley copy edited it!)
    – Peter Mortensen
    Commented May 23, 2022 at 14:50
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The answers about advantages and disadvantages of Expo and React Native CLI are complete. I want to mention another point as my personal experience.

Expo contains many modules by default in the project and it makes easier to work with it. But it has a big problem in the production phase, because the built Android and iOS versions have such a great size. For example, if you have a single page with a 'Hello, World!', the APK file size would be about 19 MB. Having a same project in React Native CLI will result in an app with the size of 6 MB.

So personally I do not recommend using Expo if you want to develop a commercial app.

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    I dont think this is a good enough reason for expo apps to not be production ready. Besides this has been thoroughly explained by previous answers
    – Dawoodjee
    Commented May 28, 2020 at 8:43
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Expo is a wrapper of React Native CLI, which does things under the hood for the ease of developers. The most common problem that Expo solves is that the developer doesn't have to worry about the linking issues of the libraries that often occur in React Native CLI. Expo comes up with tons of libraries now that are extremely helpful for robust development. One of the benefits of Expo is you can develop an app for Android and iOS without having a Mac through Expo mobile application.

As it has tons of benefits, there are some cons of using Expo:

  • App size increases like hell. A simple Hello, World! app size is more than 30 MB
  • At times when you need to implement some native functionality into your app, you will need to eject from Expo and go back to React Native CLI. And you can never revert it back to Expo CLI.
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I would make a note here that Expo is using an older version of React, 16.5, which would prohibit you from using the new hooks feature.

If you decide to go with Expo, be mindful to watch your version controls. Older versions of, say, react-navigation will need to be used with the 16.5 version if you are getting weird errors.

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  • expo update does a pretty good job of getting the compatible versions for most of the packages managed by Expo. As of right now, I don't think it updates React Navigation, but that library is actually sponsored by Expo. Personally, I rarely run into compatibility issues between React Navigation and Expo (I think I encountered a couple issues when using beta versions). However, you may see more compatibility issues with packages not managed by Expo.
    – Jon Doe
    Commented Apr 12, 2020 at 16:58
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I've experienced more than a year that works with Expo. If the size of the app is not important for you, use Expo because it's easy to implement Map and Push easier than React-native, but at the end of the project, if you want to publish app in Google Play or another store, you have a challenge removing some permissions in your APK.

In React Native you can change everything, but for importing some library, such as push notification or the map, it needs some challenges too, because you have to add these libraries manually to Android and iOS projects.

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  • What if you need to use a third-party SDK, but there is only an Android AAR available, can you integrate this AAR into your Expo-based project?
    – Zijian
    Commented Oct 17, 2021 at 5:54
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A summary of the documentation and answers from Expo employees:

React Native init: Advantages

You can add native modules written in Java or Objective-C (probably the only but the strongest one)

Disadvantages Needs Android Studio and Xcode to run the projects You can't develop for iOS without having a Mac Device has to be connected via USB to use it for testing Fonts need to be imported manually in Xcode If you want to share the app you need to send the whole .apk / .ipa file Does not provide JavaScript APIs out of the box, e.g., Push-Notifications, Asset Manager, they need to be manually installed and linked with npm for example Setting up a working project properly (including device configuration) is rather complicated and can take time

Expo Advantages

Setting up a project is easy and can be done in minutes You (and other people) can open the project while you're working on it Sharing the app is easy (via a QR code or link), you don't have to send the whole .apk or .ipa file No build necessary to run the app Integrates some basic libraries in a standard project (Push Notifications, Asset Manager, etc.) You can eject it to ExpoKit and integrate native code continuing using some of the Expo features, but not all of them Expo can build .apk and .ipa files (distribution to stores possible with Expo)

Disadvantages You can't add native modules (probably a game changer for some) You can't use libraries that use native code in Objective-C/Java The standard Hello World app is about 25MB big (because of the integrated libraries) If you want to use: FaceDetector, ARKit, or Payments you need to eject it to ExpoKit Ejecting it to ExpoKit has a trade-off of features of Expo, e.g. you cannot share via a QR code When ejecting to ExpoKit you are limited to the react-native version that is supported by ExpoKit then Debugging in ExpoKit (with native modules) is a lot more complicated, since it mixes two languages and different libraries (no official Expo support any more)

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React Native CLI

React Native CLI is a built-in feature that helps you take control over the management of the project locally. You can create and run your applications. You can create a project by simply using this command.

npx react-native init <ProjectName>

To run a project, you can run the following commands.

cd <Project Name> // or open via directory

// For Android 

npx react-native run-android 

// For IOS
npx react-native run-ios

Expo

Expo [https://docs.expo.dev/] CLI is built on top of React Native and it is the fastest way to set up your react native project in a zoom! You just create the project and start coding. You can install Expo CLI globally via npm:

// install expo-cli globally
   npm install -g expo-cli

Creating and running a React Native app with Expo is as simple as:

// create a project
expo init <Project Name>
cd <Project Name>
npm start # you can also use: expo start

The Verdict by React Native

React Native recommends using the React Native CLI if you are already familiar with Mobile App Development. However, if you are new to mobile app development and want to get the project quickly set up, Expo CLI is recommended.

Conclusion

So , these are comparison between Expo CLI and ReactNative

Given a detailed comparison of the perks and limitations of both frameworks, I would suggest screening through the requirements and choosing which one suits your application most.

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If you have a project requiring rapid development and have chosen React Native to build cross-platform applications, then Expo is for you. Through Expo, you can quickly develop and deploy React Native applications for iOS and Android.

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