Skills

Chapter 4 of 23

Eas Hosting

EAS service (paid).

3 minutes · 682 words · 30 sections

EAS service - costs apply. EAS Hosting is a paid Expo Application Services product with free-tier limits; production deploys use your plan’s request and bandwidth allowance. See https://expo.dev/pricing (opens in a new tab). Authoring API routes and exporting the web bundle are free and open source, and you can self-host the exported server output instead of EAS Hosting.

EAS Hosting deploys your Expo web app and API routes to Expo’s managed edge (Cloudflare Workers). Export the web bundle with npx expo export -p web and ship it with eas deploy - the same command deploys any Expo Router API routes bundled alongside it. This skill covers deploying a website, authoring API routes, and the hosting runtime; see the Deployment section below for the deploy workflow.

When to Use API Routes

Use API routes when you need:

Server-side secrets — API keys, database credentials, or tokens that must never reach the client
Database operations — Direct database queries that shouldn’t be exposed
Third-party API proxies — Hide API keys when calling external services (OpenAI, Stripe, etc.)
Server-side validation — Validate data before database writes
Webhook endpoints — Receive callbacks from services like Stripe or GitHub
Rate limiting — Control access at the server level
Heavy computation — Offload processing that would be slow on mobile

When NOT to Use API Routes

Avoid API routes when:

Data is already public — Use direct fetch to public APIs instead
No secrets required — Static data or client-safe operations
Real-time updates needed — Use WebSockets or services like Supabase Realtime
Simple CRUD — Consider Firebase, Supabase, or Convex for managed backends
File uploads — Use direct-to-storage uploads (S3 presigned URLs, Cloudflare R2)
Authentication only — Use Clerk, Auth0, or Firebase Auth instead

File Structure

API routes live in the app directory with +api.ts suffix:

app/
  api/
    hello+api.ts          → GET /api/hello
    users+api.ts          → /api/users
    users/[id]+api.ts     → /api/users/:id
  (tabs)/
    index.tsx

Basic API Route

// app/api/hello+api.ts
export function GET(request: Request) {
  return Response.json({ message: "Hello from Expo!" });
}

HTTP Methods

Export named functions for each HTTP method:

// app/api/items+api.ts
export function GET(request: Request) {
  return Response.json({ items: [] });
}

export async function POST(request: Request) {
  const body = await request.json();
  return Response.json({ created: body }, { status: 201 });
}

export async function PUT(request: Request) {
  const body = await request.json();
  return Response.json({ updated: body });
}

export async function DELETE(request: Request) {
  return new Response(null, { status: 204 });
}

Dynamic Routes

// app/api/users/[id]+api.ts
export function GET(request: Request, { id }: { id: string }) {
  return Response.json({ userId: id });
}

Request Handling

Query Parameters

export function GET(request: Request) {
  const url = new URL(request.url);
  const page = url.searchParams.get("page") ?? "1";
  const limit = url.searchParams.get("limit") ?? "10";

  return Response.json({ page, limit });
}

Headers

export function GET(request: Request) {
  const auth = request.headers.get("Authorization");

  if (!auth) {
    return Response.json({ error: "Unauthorized" }, { status: 401 });
  }

  return Response.json({ authenticated: true });
}

JSON Body

export async function POST(request: Request) {
  const { email, password } = await request.json();

  if (!email || !password) {
    return Response.json({ error: "Missing fields" }, { status: 400 });
  }

  return Response.json({ success: true });
}

Environment Variables

Use process.env for server-side secrets:

// app/api/ai+api.ts
export async function POST(request: Request) {
  const { prompt } = await request.json();

  const response = await fetch("https://api.openai.com/v1/chat/completions", {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      Authorization: `Bearer ${process.env.OPENAI_API_KEY}`,
    },
    body: JSON.stringify({
      model: "gpt-4",
      messages: [{ role: "user", content: prompt }],
    }),
  });

  const data = await response.json();
  return Response.json(data);
}

Set environment variables:

Local: Create .env file (never commit)
EAS Hosting: Use eas env:create or Expo dashboard

CORS Headers

Add CORS for web clients:

const corsHeaders = {
  "Access-Control-Allow-Origin": "*",
  "Access-Control-Allow-Methods": "GET, POST, PUT, DELETE, OPTIONS",
  "Access-Control-Allow-Headers": "Content-Type, Authorization",
};

export function OPTIONS() {
  return new Response(null, { headers: corsHeaders });
}

export function GET() {
  return Response.json({ data: "value" }, { headers: corsHeaders });
}

Error Handling

export async function POST(request: Request) {
  try {
    const body = await request.json();
    // Process...
    return Response.json({ success: true });
  } catch (error) {
    console.error("API error:", error);
    return Response.json({ error: "Internal server error" }, { status: 500 });
  }
}

Testing Locally

Start the development server with API routes:

npx expo serve

This starts a local server at http://localhost:8081 with full API route support.

Test with curl:

curl http://localhost:8081/api/hello
curl -X POST http://localhost:8081/api/users -H "Content-Type: application/json" -d '{"name":"Test"}'

Deployment to EAS Hosting

Prerequisites

npm install -g eas-cli
eas login

Deploy

Deploying ships your web bundle and any Expo Router API routes together - eas deploy handles both. The export runs whether you have a full website, an API-routes-only backend, or both.

# Export the web bundle (includes any API routes)
npx expo export -p web

# Deploy a preview (PR-style URL)
npx eas-cli@latest deploy

# Deploy to production
npx eas-cli@latest deploy --prod

Everything lands on EAS Hosting (Cloudflare Workers).

Environment Variables for Production

# Create a secret
eas env:create --name OPENAI_API_KEY --value sk-xxx --environment production

# Or use the Expo dashboard

Custom Domain

Configure in eas.json or Expo dashboard.

Automate with EAS Workflows

Deploy the website (and API routes) on every push to main with a type: deploy workflow:

.eas/workflows/deploy.yml

name: Deploy

on:
  push:
    branches:
      - main

# https://docs.expo.dev/eas/workflows/syntax/#deploy
jobs:
  deploy_web:
    type: deploy
    params:
      prod: true

Preview deploys for pull requests use the same job type with prod: false:

name: Web PR Preview

on:
  pull_request:
    types: [opened, synchronize]

jobs:
  preview:
    type: deploy
    params:
      prod: false

To author or validate workflow YAML beyond these examples, use the eas-workflows skill.

EAS Hosting Runtime (Cloudflare Workers)

API routes run on Cloudflare Workers. Key limitations:

Missing/Limited APIs

No Node.js filesystem — fs module unavailable
No native Node modules — Use Web APIs or polyfills
Limited execution time — 30 second timeout for CPU-intensive tasks
No persistent connections — WebSockets require Durable Objects
fetch is available — Use standard fetch for HTTP requests

Use Web APIs Instead

// Use Web Crypto instead of Node crypto
const hash = await crypto.subtle.digest(
  "SHA-256",
  new TextEncoder().encode("data")
);

// Use fetch instead of node-fetch
const response = await fetch("https://api.example.com");

// Use Response/Request (already available)
return new Response(JSON.stringify(data), {
  headers: { "Content-Type": "application/json" },
});

Database Options

Since filesystem is unavailable, use cloud databases:

Cloudflare D1 — SQLite at the edge
Turso — Distributed SQLite
PlanetScale — Serverless MySQL
Supabase — Postgres with REST API
Neon — Serverless Postgres

Example with Turso:

// app/api/users+api.ts
import { createClient } from "@libsql/client/web";

const db = createClient({
  url: process.env.TURSO_URL!,
  authToken: process.env.TURSO_AUTH_TOKEN!,
});

export async function GET() {
  const result = await db.execute("SELECT * FROM users");
  return Response.json(result.rows);
}

Calling API Routes from Client

// From React Native components
const response = await fetch("/api/hello");
const data = await response.json();

// With body
const response = await fetch("/api/users", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({ name: "John" }),
});

Common Patterns

Authentication Middleware

// utils/auth.ts
export async function requireAuth(request: Request) {
  const token = request.headers.get("Authorization")?.replace("Bearer ", "");

  if (!token) {
    throw new Response(JSON.stringify({ error: "Unauthorized" }), {
      status: 401,
      headers: { "Content-Type": "application/json" },
    });
  }

  // Verify token...
  return { userId: "123" };
}

// app/api/protected+api.ts
import { requireAuth } from "../../utils/auth";

export async function GET(request: Request) {
  const { userId } = await requireAuth(request);
  return Response.json({ userId });
}

Proxy External API

// app/api/weather+api.ts
export async function GET(request: Request) {
  const url = new URL(request.url);
  const city = url.searchParams.get("city");

  const response = await fetch(
    `https://api.weather.com/v1/current?city=${city}&key=${process.env.WEATHER_API_KEY}`
  );

  return Response.json(await response.json());
}

Rules

NEVER expose API keys or secrets in client code
ALWAYS validate and sanitize user input
Use proper HTTP status codes (200, 201, 400, 401, 404, 500)
Handle errors gracefully with try/catch
Keep API routes focused — one responsibility per endpoint
Use TypeScript for type safety
Log errors server-side for debugging

Submitting Feedback

If you encounter errors, misleading or outdated information in this skill, report it so Expo can improve:

npx --yes submit-expo-feedback@latest --category skills --subject "eas-hosting" "<actionable feedback>"

Only submit when you have something specific and actionable to report. Include as much relevant context as possible. If an AI agent repeatedly failed or the user had to take over an Expo task, load the expo-skill-feedback skill and follow its eval-candidate flow instead of reusing the command above.

Install this repository

$ npx skills add expo/skills

» /plugin marketplace add expo/skills

Skills install per repository, not per chapter — the CLI has no documented per-skill form, so we do not print one.

About this skill

Trigger

EAS service (paid). Deploy Expo websites and Expo Router API routes to EAS Hosting - export the web bundle, run eas deploy for production and PR preview URLs, manage environment secrets and custom domains, and work within the Cloudflare Workers runtime. Also covers authoring API routes (+api.ts handlers, HTTP methods, request handling, CORS). Use when deploying an Expo web app or API routes, setting up EAS Hosting, or configuring hosting environments and domains. Not for native builds or store releases - use the eas-app-stores skill for those.

The verbatim description from this skill’s front matter — the string an agent matches on to decide whether to load it.

Licence: MIT
Source: plugins/expo/skills/eas-hosting/SKILL.md

Colophon for this issue

Colophon

How this issue was made

Source

github.com/expo/skills, branch main, last pushed 7 August 2026.

Licence

MIT — the text of every chapter is reproduced unmodified, frontmatter included, under the upstream licence.

Discovery

23 chapters found by walking the repository tree for SKILL.md, not by matching a directory convention. 3 distinct layouts observed: .claude/skills/*/SKILL.md, plugins/expo-experiments/skills/*/SKILL.md, plugins/expo/skills/*/SKILL.md.

Issue colours

Resolved from the awesome-design-md registry — hue 276°, chroma 0.190. Two accent tones are generated per issue and each is proven against its own ground before it ships: a single accent that passes AA on both light and dark paper is arithmetically impossible.

Heading repairs

1 repair applied to this chapter so the document has one h1 and no skipped levels:

Removed “EAS Hosting”, a leading h1 that duplicated the chapter title.

Spec compliance

Every chapter satisfies the Agent Skills specification’s frontmatter rules.

Images

Images inside a chapter come from the upstream repository. Where the author gave no alternative text we mark the image decorative rather than inventing a description — a plausible caption we made up is worse than none for the reader who depends on it.

Marketplace

A plugin manifest is published at .claude-plugin/marketplace.json by Expo Team, declaring 5 plugins. It is read for editorial metadata only — never as the skill index, which is always the repository tree.

Signal

Install counts come from skills.sh. They measure downloads, not quality, and an unranked repository is not an unread one.

Agent surfaces

The whole issue is available as one markdown document at /expo/skills.md, and each chapter at its own .md URL.

Publication

Set by Skills Docs from the source repository. Body text is Literata at the reader’s chosen size and measure; code is Geist Mono. Nothing on this page was written by us except this paragraph.

EAS service - costs apply. EAS Hosting is a paid Expo Application Services product with free-tier limits; production deploys use your plan’s request and bandwidth allowance. See https://expo.dev/pricing (opens in a new tab). Authoring API routes and exporting the web bundle are free and open source, and you can self-host the exported server output instead of EAS Hosting.

When to Use API Routes

Use API routes when you need:

Server-side secrets — API keys, database credentials, or tokens that must never reach the client
Database operations — Direct database queries that shouldn’t be exposed
Third-party API proxies — Hide API keys when calling external services (OpenAI, Stripe, etc.)
Server-side validation — Validate data before database writes
Webhook endpoints — Receive callbacks from services like Stripe or GitHub
Rate limiting — Control access at the server level
Heavy computation — Offload processing that would be slow on mobile

When NOT to Use API Routes

Avoid API routes when:

Data is already public — Use direct fetch to public APIs instead
No secrets required — Static data or client-safe operations
Real-time updates needed — Use WebSockets or services like Supabase Realtime
Simple CRUD — Consider Firebase, Supabase, or Convex for managed backends
File uploads — Use direct-to-storage uploads (S3 presigned URLs, Cloudflare R2)
Authentication only — Use Clerk, Auth0, or Firebase Auth instead

File Structure

API routes live in the app directory with +api.ts suffix:

app/
  api/
    hello+api.ts          → GET /api/hello
    users+api.ts          → /api/users
    users/[id]+api.ts     → /api/users/:id
  (tabs)/
    index.tsx

Basic API Route

// app/api/hello+api.ts
export function GET(request: Request) {
  return Response.json({ message: "Hello from Expo!" });
}

HTTP Methods

Export named functions for each HTTP method:

// app/api/items+api.ts
export function GET(request: Request) {
  return Response.json({ items: [] });
}

export async function POST(request: Request) {
  const body = await request.json();
  return Response.json({ created: body }, { status: 201 });
}

export async function PUT(request: Request) {
  const body = await request.json();
  return Response.json({ updated: body });
}

export async function DELETE(request: Request) {
  return new Response(null, { status: 204 });
}

Dynamic Routes

// app/api/users/[id]+api.ts
export function GET(request: Request, { id }: { id: string }) {
  return Response.json({ userId: id });
}

Request Handling

Query Parameters

export function GET(request: Request) {
  const url = new URL(request.url);
  const page = url.searchParams.get("page") ?? "1";
  const limit = url.searchParams.get("limit") ?? "10";

  return Response.json({ page, limit });
}

Headers

export function GET(request: Request) {
  const auth = request.headers.get("Authorization");

  if (!auth) {
    return Response.json({ error: "Unauthorized" }, { status: 401 });
  }

  return Response.json({ authenticated: true });
}

JSON Body

export async function POST(request: Request) {
  const { email, password } = await request.json();

  if (!email || !password) {
    return Response.json({ error: "Missing fields" }, { status: 400 });
  }

  return Response.json({ success: true });
}

Environment Variables

Use process.env for server-side secrets:

// app/api/ai+api.ts
export async function POST(request: Request) {
  const { prompt } = await request.json();

  const response = await fetch("https://api.openai.com/v1/chat/completions", {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      Authorization: `Bearer ${process.env.OPENAI_API_KEY}`,
    },
    body: JSON.stringify({
      model: "gpt-4",
      messages: [{ role: "user", content: prompt }],
    }),
  });

  const data = await response.json();
  return Response.json(data);
}

Set environment variables:

Local: Create .env file (never commit)
EAS Hosting: Use eas env:create or Expo dashboard

CORS Headers

Add CORS for web clients:

const corsHeaders = {
  "Access-Control-Allow-Origin": "*",
  "Access-Control-Allow-Methods": "GET, POST, PUT, DELETE, OPTIONS",
  "Access-Control-Allow-Headers": "Content-Type, Authorization",
};

export function OPTIONS() {
  return new Response(null, { headers: corsHeaders });
}

export function GET() {
  return Response.json({ data: "value" }, { headers: corsHeaders });
}

Error Handling

export async function POST(request: Request) {
  try {
    const body = await request.json();
    // Process...
    return Response.json({ success: true });
  } catch (error) {
    console.error("API error:", error);
    return Response.json({ error: "Internal server error" }, { status: 500 });
  }
}

Testing Locally

Start the development server with API routes:

npx expo serve

This starts a local server at http://localhost:8081 with full API route support.

Test with curl:

curl http://localhost:8081/api/hello
curl -X POST http://localhost:8081/api/users -H "Content-Type: application/json" -d '{"name":"Test"}'

Deployment to EAS Hosting

Prerequisites

npm install -g eas-cli
eas login

Deploy

Deploying ships your web bundle and any Expo Router API routes together - eas deploy handles both. The export runs whether you have a full website, an API-routes-only backend, or both.

# Export the web bundle (includes any API routes)
npx expo export -p web

# Deploy a preview (PR-style URL)
npx eas-cli@latest deploy

# Deploy to production
npx eas-cli@latest deploy --prod

Everything lands on EAS Hosting (Cloudflare Workers).

Environment Variables for Production

# Create a secret
eas env:create --name OPENAI_API_KEY --value sk-xxx --environment production

# Or use the Expo dashboard

Custom Domain

Configure in eas.json or Expo dashboard.

Automate with EAS Workflows

Deploy the website (and API routes) on every push to main with a type: deploy workflow:

.eas/workflows/deploy.yml

name: Deploy

on:
  push:
    branches:
      - main

# https://docs.expo.dev/eas/workflows/syntax/#deploy
jobs:
  deploy_web:
    type: deploy
    params:
      prod: true

Preview deploys for pull requests use the same job type with prod: false:

name: Web PR Preview

on:
  pull_request:
    types: [opened, synchronize]

jobs:
  preview:
    type: deploy
    params:
      prod: false

To author or validate workflow YAML beyond these examples, use the eas-workflows skill.

EAS Hosting Runtime (Cloudflare Workers)

API routes run on Cloudflare Workers. Key limitations:

Missing/Limited APIs

No Node.js filesystem — fs module unavailable
No native Node modules — Use Web APIs or polyfills
Limited execution time — 30 second timeout for CPU-intensive tasks
No persistent connections — WebSockets require Durable Objects
fetch is available — Use standard fetch for HTTP requests

Use Web APIs Instead

// Use Web Crypto instead of Node crypto
const hash = await crypto.subtle.digest(
  "SHA-256",
  new TextEncoder().encode("data")
);

// Use fetch instead of node-fetch
const response = await fetch("https://api.example.com");

// Use Response/Request (already available)
return new Response(JSON.stringify(data), {
  headers: { "Content-Type": "application/json" },
});

Database Options

Since filesystem is unavailable, use cloud databases:

Cloudflare D1 — SQLite at the edge
Turso — Distributed SQLite
PlanetScale — Serverless MySQL
Supabase — Postgres with REST API
Neon — Serverless Postgres

Example with Turso:

// app/api/users+api.ts
import { createClient } from "@libsql/client/web";

const db = createClient({
  url: process.env.TURSO_URL!,
  authToken: process.env.TURSO_AUTH_TOKEN!,
});

export async function GET() {
  const result = await db.execute("SELECT * FROM users");
  return Response.json(result.rows);
}

Calling API Routes from Client

// From React Native components
const response = await fetch("/api/hello");
const data = await response.json();

// With body
const response = await fetch("/api/users", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({ name: "John" }),
});

Common Patterns

Authentication Middleware

// utils/auth.ts
export async function requireAuth(request: Request) {
  const token = request.headers.get("Authorization")?.replace("Bearer ", "");

  if (!token) {
    throw new Response(JSON.stringify({ error: "Unauthorized" }), {
      status: 401,
      headers: { "Content-Type": "application/json" },
    });
  }

  // Verify token...
  return { userId: "123" };
}

// app/api/protected+api.ts
import { requireAuth } from "../../utils/auth";

export async function GET(request: Request) {
  const { userId } = await requireAuth(request);
  return Response.json({ userId });
}

Proxy External API

// app/api/weather+api.ts
export async function GET(request: Request) {
  const url = new URL(request.url);
  const city = url.searchParams.get("city");

  const response = await fetch(
    `https://api.weather.com/v1/current?city=${city}&key=${process.env.WEATHER_API_KEY}`
  );

  return Response.json(await response.json());
}

Rules

NEVER expose API keys or secrets in client code
ALWAYS validate and sanitize user input
Use proper HTTP status codes (200, 201, 400, 401, 404, 500)
Handle errors gracefully with try/catch
Keep API routes focused — one responsibility per endpoint
Use TypeScript for type safety
Log errors server-side for debugging

Submitting Feedback

If you encounter errors, misleading or outdated information in this skill, report it so Expo can improve:

npx --yes submit-expo-feedback@latest --category skills --subject "eas-hosting" "<actionable feedback>"

About this skill

Trigger

Colophon

Appendix 4.1

Also bundledYAML · 1 file

About this skill

Trigger

Colophon

Appendix 4.1

Also bundledYAML · 1 file