Limitations
Your success will be limited if you don't know the limitations of your tools. A good software engineer strives to understand the tradeoffs in the decisions they make.
Used Expo before? Here are some recent changes to the managed workflow you should be aware of…
With the release of Expo Application Services, the managed workflow has far fewer limitations, and can be used for any project no matter the complexity:
- All libraries available to React Native apps are available to Expo managed workflow apps built with EAS Build, but some may require a Prebuild Config Plugin to be added. The addition of config plugins means:
- Any 3rd party push notification service can support managed workflow apps.
- Native libraries that integrate with proprietary services can support managed workflow apps.
- Apps built with EAS Build can be as small as you want since the entire Expo SDK is no longer bundled in by default.
- Apps built with EAS Build can target children under 13 years old.
These changes mean Expo can fit many more use cases than before.
If you're still using expo build:ios or expo build:android, or using Expo Go for development, it's important to be aware of the limitations that come with those features.
If you'd like to continue getting the same development experience that you have with Expo Go, but also use custom native libraries or custom native code, you should check out the
Expo Dev Client!
Expo Go comes with a pre-configured set of libraries, known as the Expo SDK. This makes development much faster, and essentially makes the mobile development experience much closer to the web development experience. However, additional native code cannot be added to Expo Go on the fly, so this means you are limited in terms of what dependencies you can add. This also applies to apps built with expo build:android and expo build:ios.
Not all iOS and Android APIs are available
Many device APIs are supported (check out the "SDK API Reference" in the sidebar), but
not all iOS and Android APIs are available yet. We are constantly adding new APIs, so if we don't have something you need now, you can either use
EAS Build, the
bare workflow, or follow
our blog to see the release notes for our SDK updates. Feature prioritization isn't strictly based off of popular vote, but it certainly helps us to gauge what is important to users.
If you need to keep your app size extremely lean, expo build:[android|ios] may not be the best choice
The size for an app built with
expo build on iOS is approximately 20mb (download), and Android is about 15mb. This is because a bunch of APIs are included regardless of whether or not you are using them — this lets you publish updates that use new APIs, but comes at the cost of binary size. Some of the APIs that are included are tied to services that you may not be using, for example, the Facebook Mobile SDK is included to support Facebook Login and Facebook Ads, along with the Google Mobile SDK for similar reasons.
Read more about managing your app size here.
If you'd like a smaller app size, you should use
EAS Build.
Native libraries to integrate with proprietary services are usually not included in the SDK
Related to the previous point, we typically avoid adding native modules to the SDK if they are tied to external, proprietary services — we can't add something to the SDK just because a few users need it for their app, we have to think of the broader userbase. In these cases developers will want to use
EAS Build, or the
bare workflow.
The only supported third-party push notification service is the Expo notification service
The minimum supported OS versions are Android 5+ and iOS 10+
If you need to support older versions, you will not be able to use expo build:ios or expo build:android.
Free builds can sometimes be queued
You can easily build your app for submission to stores without even installing Xcode or Android Studio by using the free
standalone build service, but it occasionally has a queue depending on how many other folks are building a binary at that time. You can have access to dedicated build infrastructure with a
"Priority" plan, or you can
run the builds on your own CI if you prefer.
Your app cannot target only children under 13 years old without customizing native dependencies
Both
Apple and
Google provide strict guidelines for any apps that specifically target children under a particular age. One of these guidelines states that certain ad libraries, such as Facebook's Audience Network, cannot be used in the app.
Apps built with
expo build:ios|android contain code for the entire Expo SDK, you cannot customize the native dependencies, including Facebook's Audience Network library, so if you build your app this way you cannot designated it as "designed primarily for children under 13" in the App Store or Play Store,
even though this code is never run unless you explicitly call it.
We are either actively working on or planning to build solutions to all of the limitations listed above, and if you think anything is missing, please bring it to our attention by posting to our
feature requests board or the
forums.
In the bare workflow, we have full access to the underlying native projects and any native code. It's a "bare" native project with React Native and one or more packages from the Expo SDK installed. Anything that you can do in a native project is possible here.
The following list is therefore specifically oriented towards the limitations that exist around using Expo tools and services in the bare workflow.
Build service only works in the managed workflow (✅ Resolved in December 2020)
To build your app binaries for distribution on the Apple App Store and Google Play Store you will need to follow the same steps that you would in any native project, the Expo build service can't handle it for you. We are working on bringing bare workflow support to the build service in the near future.
Configuration must be done on each native project rather than once with app.json
Configuring app icons, launch screen, and so on must be configured in the native projects for each platform using the standard native tooling, rather than once using a simple JSON object.
If you've been reading along each section of the introduction then you will have a pretty good high-level understanding of Expo tools.