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What Is Expo? A Comprehensive Guide for Mobile App Development

July 4, 2025

This guide provides a comprehensive overview of the Expo ecosystem, detailing its tools, workflows, and real-world use cases for building cross-platform mobile applications. Let our team of experts show you how we can integrate Expo into your product for accelerated growth and a superior user experience.

Chris Fitkin

Chris Fitkin

Founding Partner

What Is Expo? A Comprehensive Guide for Mobile App Development logo

Introduction to Expo

In the world of mobile app development, efficiency and reach are paramount. Developers constantly seek tools that can streamline the process of building high-quality applications that run seamlessly on multiple platforms. This is where Expo enters the picture. Expo is not a programming language, but rather a powerful, open-source platform and ecosystem of tools built around React Native. It is designed to help developers create universal native apps for Android, iOS, and the web using a single JavaScript and React codebase.

Expo is the home for developers aiming to build native apps across both major mobile operating systems with the flexibility and power of JavaScript. It functions as a complete ecosystem, providing a suite of tools that assist with every stage of the application lifecycle: from initializing a new project and writing code to building, deploying, updating, and monitoring the final product. Whether you are starting a new project from scratch or want to bring an existing React Native project into a more managed and efficient workflow, Expo provides the necessary tooling.

At its core, Expo is about accelerating development and simplifying complexity. It offers a free plan to get started, making it accessible to individual developers and large teams alike. With services and tools designed to help you ship faster, Expo handles many of the tedious and error-prone aspects of mobile development, allowing you to focus on what matters most: building a great user experience.

How Expo Works

To understand Expo, it’s essential to recognize that it’s not a monolithic entity. Instead, it is a collection of powerful tools and services that can be adopted independently or used together for a seamless development experience. An “Expo app” is simply a React Native app that leverages one or more of these tools, whether it’s the Expo CLI, the Expo Router for file-based routing, or the extensive Expo SDK.

The Two Pillars: Open-Source Tools and Expo Application Services (EAS)

The Expo ecosystem is built on two main pillars: its free, open-source tools and its hosted cloud services, known as Expo Application Services (EAS).

  • Expo Open-Source Tools: These are the foundational components that are free for everyone to use under the permissive MIT license. They give developers the power to build and maintain their React Native apps with greater ease. Key examples include:

    • Expo CLI: The command-line interface for creating, managing, and running Expo projects.
    • Expo Router: A powerful file-based routing library that simplifies navigation in your app.
    • Expo SDK: A collection of over 75 premade modules that provide access to device APIs like the camera, file system, and sensors, without needing to write native code.
  • Expo Application Services (EAS): EAS is a suite of hosted services designed to work with both Expo and standard React Native projects. While the open-source tools help you write your app, EAS helps you ship it. It solves complex problems that require physical resources, such as managing build servers or content delivery networks (CDNs). EAS can be used to:

    • Build your app in the cloud, creating store-ready binaries for Android and iOS.
    • Submit your app automatically to the Apple App Store and Google Play Store.
    • Update your app’s JavaScript code and assets over-the-air, allowing you to publish bug fixes in minutes without a full store review.
    • Collaborate with your team through shared credentials, roles, and build logs.
    • Automate your entire release process using Workflows.

While EAS provides a deeply integrated, managed experience, it also offers flexibility. For teams that require it, most EAS services can be run on your own infrastructure, and instructions are provided for self-hosting updates or running builds on your own CI.

The Development Workflow: Continuous Native Generation

One of the most innovative aspects of the Expo workflow is a process called Continuous Native Generation (CNG). When you initialize a new app with the command npx create-expo-app, you’ll notice that the android and ios directories, which contain the native project code, are not created by default.

This is intentional. CNG is a process where the native projects are generated on-demand directly from your project’s configuration, primarily the app.json (or app.config.js) and package.json files. This is conceptually similar to how your project’s node_modules directory is generated from the dependencies listed in package.json. You don’t commit node_modules to your version control; you simply run npm install to generate it.

With CNG, you can treat your native project folders the same way. You can add them to your .gitignore, delete them at any time, and regenerate them perfectly by running npx expo prebuild. This approach has several major advantages:

  • Easier Upgrades: Upgrading to new versions of React Native becomes much simpler, as you are not managing complex native code changes directly.
  • Simplified Maintenance: Your project’s “source of truth” is your JavaScript code and configuration files, not brittle native project files.
  • Complex Feature Setup: CNG, powered by “config plugins,” facilitates the setup of complex native features like push notifications, share extensions, and App Clips by automating the necessary native configuration.

Of course, developers still have the option to “eject” from this managed workflow. You can run npx expo prebuild once and then begin modifying the android and ios directories directly. However, doing so means you can no longer safely re-generate the projects, as prebuild would overwrite your manual changes.

Prototyping and Full Development

Expo provides different tools for different stages of development.

  • Expo Go: For learning, rapid prototyping, and experimentation, Expo Go is an invaluable tool. It’s a client app that you install on your phone or simulator. Paired with Snack, a web-based playground, you can spin up a React Native project and run it on a real device in seconds just by scanning a QR code. However, Expo Go is not intended for building production apps, as it has limitations on which native libraries you can use.

  • Development Builds: For full-featured development, you will create a development build. This is a debug version of your actual app that contains the expo-dev-client library. A development build provides a more flexible, reliable, and complete environment. It allows you to:

    • Install and use any third-party native library.
    • Write your own custom native code.
    • Iterate quickly with features like fast refresh.
    • Apply custom native configurations using config plugins.

You can create development builds either locally on your machine or in the cloud using EAS Build.

How to Use Expo

The Expo ecosystem is designed to be flexible, supporting developers whether they prefer a cloud-based or a local development workflow. Here’s a conceptual overview of the journey from project creation to app store release.

1. Project Initialization and Setup

The journey begins with a single command:

npx create-expo-app my-app

This scaffolds a new, universal React Native project. Immediately after creation, you can launch the project in Expo Go on your device or an emulator for initial experimentation. For most real-world projects, the next step is to create a development build by installing the expo-dev-client library.

2. Choosing a Compilation Workflow: Cloud vs. Local

A key decision in the Expo workflow is whether to compile your app’s native code in the cloud or on your local machine. This is a choice you can make each time you run a build.

  • Cloud Compilation with EAS Build: By running a single command in your terminal, you can send your project to Expo’s servers, which will compile and sign your app. This approach is powerful because it requires no installation of Android Studio or Xcode on your machine. It also makes sharing builds with teammates or stakeholders for review incredibly easy.

  • Local Compilation: To compile locally, you need the standard mobile development toolchains installed (Android Studio for Android, Xcode for macOS/iOS). You can then build and run your app using commands like npx expo run:android or npx expo run:ios. This method is particularly useful for debugging issues that require native debugging tools on a physical device or simulator.

3. The Core Development Loop

Once your development environment is set up, the core loop of building your app involves several key activities:

  • Writing JavaScript: You’ll spend most of your time writing React components and application logic in JavaScript or TypeScript. Expo offers fast refresh, so changes are reflected in your development build almost instantly.
  • Updating App Configuration: You can easily update your app’s name, icon, splash screen, version number, and other metadata through the central app.json or app.config.js file.
  • Installing Libraries: The React Native ecosystem is vast. With a development build, you can use any library or SDK. If a library requires native code modifications, it will typically come with a config plugin that automatically handles the setup when you rebuild.
  • Writing Native Code: If your app requires functionality not available in an existing module, Expo allows you to write your own native code. You can access every device API and build truly custom features.

4. Building, Reviewing, and Submitting

When you’re ready to move beyond development, Expo and EAS streamline the release process.

  • Create App Store-Ready Builds: Using EAS Build, you can create signed, optimized builds for production.
  • Team Review: Invite your team members with adjustable roles to contribute, test, and view the state of deployments. You can upgrade PR reviews with ad-hoc builds that can be installed directly on a device. EAS also supports running automated end-to-end tests with Maestro.
  • Automatic Submission: EAS Submit can automatically upload your builds to the Apple App Store and Google Play Store, managing credentials and metadata for you.

5. Post-Launch Updates and Monitoring

The lifecycle of an app doesn’t end at launch. Expo provides powerful tools for maintenance and growth.

  • Over-the-Air (OTA) Updates: Using the expo-updates library and EAS Update, you can push JavaScript and asset updates directly to your users’ devices in minutes. This is perfect for shipping critical bug fixes or small feature changes without going through a full app store review process. EAS Update serves these updates from a global CDN for maximum speed and reliability.
  • Monitoring and Rollbacks: Web dashboards keep your team on track by providing a clear view of all builds, submissions, and deployments. If an update introduces a problem, you have the ability to roll it back in seconds, ensuring a stable experience for your users.

Use Cases for Expo

Expo is not just for small projects or simple apps. It is a production-grade platform trusted by some of the world’s leading companies to build and maintain their flagship mobile applications. Its versatility is demonstrated by its adoption across a wide range of industries. Below is a sample of well-known apps built with Expo, showcasing its capability to handle diverse and complex requirements.

CategoryExample Apps Built with Expo
Finance & BankingCoinbase, DailyPay On-Demand Pay, Chime – Mobile Banking, Mission Lane Card, Bloom – Learn to Invest, Novus World
Food & DeliveryBURGER KING® App, Pizza Hut – Delivery & Takeout, sweetgreen, Just Salad, Delicio: AI Chef, Food Recipes
SportsPikkit: Sports Betting Tracker, GoFan: Buy Tickets to Events, HotStreak Fantasy Sports, GolfPass, Juice Reel: Bet Tracker & Tips
ShoppingPUMA, GameStop, Cameo – Personal Celeb Videos, Goody – Easy Gifting, Dupe.com
BusinessAmazon A to Z, Shipt Shopper: Shop for Pay, Brex, Mystro Driver: Drive & Deliver, NetConnect for Clean Internet
Social NetworkingBluesky Social
EntertainmentStubHub: Event Tickets, Vivid Seats
NewsBusiness Insider, Newsrael, DP+
LifestylePartiful Invites, Testla
Medical & HealthMyBSWHealth, Solv: Easy Same-Day Healthcare, Carby Health, Cerebral – Mental Health
EducationBrightspace Pulse, Lingvano: Sign Language – ASL, BoldVoice: Accent Training, Prodigy Math Game, British Museum Audio

As this list demonstrates, Expo is a robust choice for building everything from complex financial trading platforms and high-traffic e-commerce storefronts to engaging social networks and critical healthcare applications. Its ability to provide a consistent user experience across Android and iOS while accelerating development cycles makes it an attractive option for businesses of all sizes.

Similar Services and Products in the Ecosystem

While Expo provides a comprehensive, all-in-one ecosystem, it’s helpful to understand how it fits within the broader landscape of mobile app development. The tools below are not necessarily direct competitors but are part of the same world and can sometimes be used in conjunction with or as alternatives to parts of the Expo workflow.

React Native CLI

React Native is the foundational technology that Expo is built upon. You can build a React Native app without using any of Expo’s tools, a workflow often referred to as “vanilla” or “bare” React Native. This involves using the standard React Native CLI. In this scenario, you are responsible for managing the android and ios native project files directly from the beginning. While this offers maximum control, it also requires deep knowledge of native development for both platforms and involves significantly more manual configuration for linking libraries, setting up build variants, and managing upgrades. Expo’s tools, especially Continuous Native Generation and config plugins, were created to abstract away much of this complexity.

Fastlane

Before services like EAS Submit existed, Fastlane was the go-to open-source tool for automating the build and release process for mobile apps. It provides a suite of tools to handle tasks like generating screenshots, dealing with code signing, and uploading builds to the app stores. An Expo project can still use Fastlane for these tasks. However, EAS Submit offers a more deeply integrated solution within the Expo ecosystem, managed via the cloud and a simple CLI, which can be simpler for teams that want an all-in-one solution.

Native IDEs: Android Studio and Xcode

As mentioned, local compilation of a React Native app requires the native Integrated Development Environments (IDEs): Android Studio for Android and Xcode for iOS. These powerful tools are the standard for native platform development and offer sophisticated debugging and performance profiling capabilities. Expo doesn’t replace them but offers a workflow (EAS Build) where developers may never need to install or open them. When you choose local compilation with npx expo run, Expo is effectively automating these tools for you. They remain essential for certain deep-level native debugging tasks.

The Challenges of Expo and Why a Partner Can Help

While Expo provides immense power and simplifies many aspects of mobile development, it is a sophisticated ecosystem that comes with its own set of challenges. One of the most prominent is the need for constant updates. Expo is a fast-moving project, and its SDK versions are deprecated on a regular basis. This requires developers to keep their Expo version, dependencies, and native configurations up to date to ensure security and compatibility.

This continuous need for updates can lead to significant overhead, especially for larger projects or applications that rely on custom native modules. An upgrade that seems simple on the surface can sometimes lead to a cascade of breaking changes that require careful navigation. This is where partnering with a specialized mobile app development agency like MetaCTO can be a strategic advantage.

As a team with over 20 years of app development experience and more than 120 successful projects under our belt, we have the expertise to navigate the complexities of the Expo ecosystem. When you work with us, you get access to a full team of experts, including UI/UX designers, front-end and back-end developers, project managers, and QA testers. We handle the technical strategy, design, user flows, and rigorous testing required for a successful app.

Our process ensures we build the right product from day one. We guide our clients through a discovery phase that includes market research, competitor analysis, and user journey mapping. This meticulous planning, managed by a dedicated project manager, ensures timely delivery and budget adherence. More importantly, we provide ongoing support and maintenance. We manage the crucial task of keeping your app aligned with Expo updates, security patches, and platform changes, saving you from costly downtimes and technical debt. Our expertise in mobile app development allows you to harness the speed and power of Expo without shouldering the maintenance burden.

Conclusion

Expo stands as a transformative force in the world of mobile app development. It provides an open-source platform and a rich ecosystem of tools that empower developers to build high-quality, universal native applications for iOS, Android, and the web from a single React codebase. We’ve explored how Expo works, from its foundational open-source tools and powerful EAS cloud services to its innovative Continuous Native Generation workflow. We’ve seen its real-world application in production apps for global brands like Coinbase, PUMA, and Burger King, proving its capability across nearly every industry.

However, leveraging this powerful platform effectively requires expertise. The fast-paced nature of Expo’s development and the complexities of managing a cross-platform project can present significant challenges. By partnering with an experienced agency, you can mitigate these risks and ensure your project’s success. An expert team can handle the technical intricacies of updates and integrations, allowing you to focus on your business goals.

To leverage the full power of Expo without the overhead, talk to one of our Expo experts at MetaCTO. We can help you integrate Expo into your product, whether you’re building a new MVP from scratch or bringing an existing project to the next level.

Last updated: 04 July 2025

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