Reference version

Server-side API and runtime for Expo Router projects.

Server

expo-server is a server-side API and runtime library for Expo Router. It provides helpers you can use in your Expo Router API routes or other server code, and contains adapters to run Expo Router server exports.

Installation

Terminal
npx expo install expo-server

To use expo-server in your project, you need to configure your Expo Router project to export in server mode. Follow the instructions from Expo Router's API Routes guide:

API Routes

Learn how to create server endpoints with Expo Router.

Usage

expo-server's runtime APIs can only be used in server-side code and give you access to the server-side runtime environment. The runtime API exposes functions that can be called within the async context of request handlers and give you information about the current request or schedule tasks that run concurrently to the incoming request.

Accessing request metadata

import { origin, environment } from 'expo-server'; export async function GET() { return Response.json({ isProduction: environment() == null, isStating: environment() === 'staging', origin: origin(), }); }

Scheduling tasks

import { runTask, deferTask } from 'expo-server'; export async function GET() { runTask(async () => { console.log('will run immediately.'); }); deferTask(async () => { console.log('will run after the response resolved.'); }); return Response.json({ success: true }); }

Adapters

expo-server exposes adapters to run Expo Router server-side exports in different environments or on different cloud provider serverless functions. Typically, every runtime needs its own adapter to function with the expo-server runtime. Before deploying to these providers, it is good to be familiar with the basics of npx expo export command.

AdapterProvider
expo-server/adapter/bunBun
expo-server/adapter/expressExpress
expo-server/adapter/httpNode.js
expo-server/adapter/netlifyNetlify Functions
expo-server/adapter/vercelVercel Functions
expo-server/adapter/workerdCloudflare Workers

To learn how to host API routes on different third-party services, follow the instructions from Expo Router's API Routes guide:

API Routes

Learn how to host API Routes on third-party services.

By convention, all adapters export a createRequestHandler function that accepts a parameters object. This accepts a build parameter that must be set to the relative path to the dist/server output directory that npx expo export created. Some adapters may also accept more values to configure the runtime API.

import path from 'node:path'; import { createRequestHandler } from 'expo-server/adapter/http'; const onRequest = createRequestHandler({ build: path.join(process.cwd(), 'dist/server'), environment: process.env.NODE_ENV, });

API

Classes

StatusError

Server

Type: Class extends Error

An error response representation which can be thrown anywhere in server-side code.

A StatusError can be thrown by a request handler and will be caught by the expo-server runtime and replaced by a Response with the status and body that's been passed to the StatusError.

Example

import { StatusError } from 'expo-server'; export function GET(request, { postId }) { if (!postId) { throw new StatusError(400, 'postId parameter is required'); } }

StatusError Properties

body

Server
Type: string

status

Server
Type: number

Methods

deferTask(fn)

Server
ParameterTypeDescription
fn() => Promise<unknown>

A task function to execute after the request handler has finished.


Defers a task until after a response has been sent.

This only calls the task function once the request handler has finished resolving a Response and keeps the request handler alive until the task is completed. This is useful to run non-critical tasks after the request handler, for example to log analytics datapoints. If the request handler rejects with an error, deferred tasks won't be executed.

Returns:
void

environment()

Server

Returns the request's environment, if the server runtime supports this.

In EAS Hosting, the returned environment name is the alias or deployment identifier, but the value may differ for other providers.

Returns:
string | null

A request environment name, or null for production.

origin()

Server

Returns the current request's origin URL.

This typically returns the request's Origin header, which contains the request origin URL or defaults to null.

Returns:
string | null

A request origin

runTask(fn)

Server
ParameterTypeDescription
fn() => Promise<unknown>

A task function to execute. The request handler will be kept alive until this task finishes.


Runs a task immediately and instructs the runtime to complete the task.

A request handler may be terminated as soon as the client has finished the full Response and unhandled promise rejections may not be logged properly. To run tasks concurrently to a request handler and keep the request alive until the task is completed, pass a task function to runTask instead. The request handler will be kept alive until the task completes.

Returns:
void

Interfaces

ImmutableRequest

Server

Extends: _ImmutableRequest

An immutable version of the Fetch API's Request as received by middleware functions. It cannot be mutated or modified, its headers are immutable, and you won't have access to the request body.

PropertyTypeDescription
methodstring

The method read-only property of the POST, etc.) A String indicating the method of the request.

MDN Reference

urlstring

The url read-only property of the Request interface contains the URL of the request.

MDN Reference

MiddlewareMatcher

Server

Middleware matcher settings that restricts the middleware to run conditionally.

PropertyTypeDescription
methods(optional)string[]

Set this to a list of HTTP methods to conditionally run middleware on. By default, middleware will match all HTTP methods.

Example

['POST', 'PUT', 'DELETE']

patterns(optional)(string | RegExp)[]

Set this to a list of path patterns to conditionally run middleware on. This may be exact paths, paths containing parameter or catch-all segments ('/posts/[postId]' or '/blog/[...slug]'), or regular expressions matching paths.

Example

['/api', '/posts/[id]', '/blog/[...slug]']

MiddlewareSettings

Server

Exported from a +middleware.ts file to configure the server-side middleware function.

Example

import type { MiddlewareSettings } from 'expo-server'; export const unstable_settings: MiddlewareSettings = { matcher: { methods: ['GET'], patterns: ['/api', '/admin/[...path]'], }, };
PropertyTypeDescription
matcher(optional)MiddlewareMatcher

Matcher definition that restricts the middleware to run conditionally.

Types

MiddlewareFunction(request)

Server

Middleware function type. Middleware run for every request in your app, or on specified conditonally matched methods and path patterns, as per MiddlewareMatcher.

Example

import type { MiddlewareFunction } from 'expo-server'; const middleware: MiddlewareFunction = async (request) => { console.log(`Middleware executed for: ${request.url}`); }; export default middleware;
ParameterTypeDescription
requestImmutableRequest

An ImmutableRequest with read-only headers and no body access

Returns:

Promise<Response | void> | Response | void