1# Cloudflare Pages Functions
2 
3Serverless functions on Cloudflare Pages using Workers runtime. Full-stack dev with file-based routing.
4 
5## Quick Navigation
6 
7**Need to...**
8| Task | Go to |
9|------|-------|
10| Set up TypeScript types | [configuration.md](./configuration.md) - TypeScript Setup |
11| Configure bindings (KV, D1, R2) | [configuration.md](./configuration.md) - wrangler.jsonc |
12| Access request/env/params | [api.md](./api.md) - EventContext |
13| Add middleware or auth | [patterns.md](./patterns.md) - Middleware, Auth |
14| Background tasks (waitUntil) | [patterns.md](./patterns.md) - Background Tasks |
15| Debug errors or check limits | [gotchas.md](./gotchas.md) - Common Errors, Limits |
16 
17## Decision Tree: Is This Pages Functions?
18 
19```
20Need serverless backend? 
21├─ Yes, for a static site → Pages Functions
22├─ Yes, standalone API → Workers
23└─ Just static hosting → Pages (no functions)
24 
25Have existing Worker?
26├─ Complex routing logic → Use _worker.js (Advanced Mode)
27└─ Simple routes → Migrate to /functions (File-Based)
28 
29Framework-based?
30├─ Next.js/SvelteKit/Remix → Uses _worker.js automatically
31└─ Vanilla/HTML/React SPA → Use /functions
32```
33 
34## File-Based Routing
35 
36```
37/functions
38  ├── index.js              → /
39  ├── api.js                → /api
40  ├── users/
41  │   ├── index.js          → /users/
42  │   ├── [user].js         → /users/:user
43  │   └── [[catchall]].js   → /users/*
44  └── _middleware.js        → runs on all routes
45```
46 
47**Rules:**
48- `index.js` → directory root
49- Trailing slash optional
50- Specific routes precede catch-alls
51- Falls back to static if no match
52 
53## Dynamic Routes
54 
55**Single segment** `[param]` → string:
56```js
57// /functions/users/[user].js
58export function onRequest(context) {
59  return new Response(`Hello ${context.params.user}`);
60}
61// Matches: /users/nevi
62```
63 
64**Multi-segment** `[[param]]` → array:
65```js
66// /functions/users/[[catchall]].js
67export function onRequest(context) {
68  return new Response(JSON.stringify(context.params.catchall));
69}
70// Matches: /users/nevi/foobar → ["nevi", "foobar"]
71```
72 
73## Key Features
74 
75- **Method handlers:** `onRequestGet`, `onRequestPost`, etc.
76- **Middleware:** `_middleware.js` for cross-cutting concerns
77- **Bindings:** KV, D1, R2, Durable Objects, Workers AI, Service bindings
78- **TypeScript:** Full type support via `wrangler types` command
79- **Advanced mode:** Use `_worker.js` for custom routing logic
80 
81## Reading Order
82 
83**New to Pages Functions?** Start here:
841. [README.md](./README.md) - Overview, routing, decision tree (you are here)
852. [configuration.md](./configuration.md) - TypeScript setup, wrangler.jsonc, bindings
863. [api.md](./api.md) - EventContext, handlers, bindings reference
874. [patterns.md](./patterns.md) - Middleware, auth, CORS, rate limiting, caching
885. [gotchas.md](./gotchas.md) - Common errors, debugging, limits
89 
90**Quick reference lookup:**
91- Bindings table → [api.md](./api.md)
92- Error diagnosis → [gotchas.md](./gotchas.md)
93- TypeScript setup → [configuration.md](./configuration.md)
94 
95## See Also
96- [pages](../pages/) - Pages platform overview and static site deployment
97- [workers](../workers/) - Workers runtime API reference
98- [d1](../d1/) - D1 database integration with Pages Functions
99