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.
As explained on the
workflows overview page, the managed workflow is kind of like "
Rails" and "
Create React App" for React Native. If you use the tools we provide in the managed workflow to build your app, we try to handle as much of the complexity of building apps for you as we can. The tradeoff here is that this workflow won't be suitable for
every possible app.
There are plenty of cases where its current constraints may not be appropriate for your project. The following is a list of limitations that we are aware of that may influence your decision on whether the managed workflow is a good fit for your project.
Many device APIs are supported (check out the "SDK API Reference" in the sidebar), but
not all iOS and Android APIs are available yet: need Bluetooth? Sorry, we haven't built support for it yet. WebRTC? Not quite. One of the most frequent requests we get is for In-App Purchases and Apple and Google Pay integration. We haven't built this yet, but it's on the roadmap. We are constantly adding new APIs, so if we don't have something you need now, you can either use 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.
Background execution is the ability to run code when the app is not foregrounded or the device is sleeping. We support background geolocation (including geofencing), background fetch, and handling notifications in the background, but we do not yet support background audio with the operating-system playback controls. This is a work in progress.
The size for a managed Expo app on iOS is approximately 20mb (download), and Android is about 15mb. This is because "managed" includes a bunch of APIs regardless of whether or not you are using them — this lets you push over-the-air updates to 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. We will make this customizable in the future, so you can trim down the size of your binaries.
Read more about managing your app size here.
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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 the
bare workflow, and they can easily migrate to it by
ejecting.
If you want to use another third-party push notification service, such as OneSignal, instead of the
Expo Push Notification service/API, you will need to use the bare workflow.
If you need to support older versions, you will not be able to use the managed workflow.
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.
Expo's current update service supports updates around 50 MiB. Updates are published both for OTA updates and to build standalone apps, which embed updates. See more about
optimizing updates.
You also can use the
bare workflow with the
expo-updates library, which supports arbitrarily large updates that are self-hosted or embedded in apps compiled on your own computer.
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.
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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 to the limitations that exist around using Expo tools and services in the bare workflow.
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.
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.