1# Cloudflare Bindings Skill Reference
2 
3Expert guidance on Cloudflare Workers Bindings - the runtime APIs that connect Workers to Cloudflare platform resources.
4 
5## What Are Bindings?
6 
7Bindings are how Workers access Cloudflare resources (storage, compute, services) via the `env` object. They're configured in `wrangler.jsonc`, type-safe via TypeScript, and zero-overhead at runtime.
8 
9## Reading Order
10 
111. **This file** - Binding catalog and selection guide
122. **[api.md](api.md)** - TypeScript types and env access patterns
133. **[configuration.md](configuration.md)** - Complete wrangler.jsonc examples
144. **[patterns.md](patterns.md)** - Best practices and common patterns
155. **[gotchas.md](gotchas.md)** - Critical pitfalls and troubleshooting
16 
17## Binding Catalog
18 
19### Storage Bindings
20 
21| Binding | Use Case | Access Pattern |
22|---------|----------|----------------|
23| **KV** | Key-value cache, CDN-backed reads | `env.MY_KV.get(key)` |
24| **R2** | Object storage (S3-compatible) | `env.MY_BUCKET.get(key)` |
25| **D1** | SQL database (SQLite) | `env.DB.prepare(sql).all()` |
26| **Durable Objects** | Coordination, real-time state | `env.MY_DO.get(id)` |
27| **Vectorize** | Vector embeddings search | `env.VECTORIZE.query(vector)` |
28| **Queues** | Async message processing | `env.MY_QUEUE.send(msg)` |
29 
30### Compute Bindings
31 
32| Binding | Use Case | Access Pattern |
33|---------|----------|----------------|
34| **Service** | Worker-to-Worker RPC | `env.MY_SERVICE.fetch(req)` |
35| **Workers AI** | LLM inference | `env.AI.run(model, input)` |
36| **Browser Rendering** | Headless Chrome | `env.BROWSER.fetch(url)` |
37 
38### Platform Bindings
39 
40| Binding | Use Case | Access Pattern |
41|---------|----------|----------------|
42| **Analytics Engine** | Custom metrics | `env.ANALYTICS.writeDataPoint(data)` |
43| **mTLS** | Client certificates | `env.MY_CERT` (string) |
44| **Hyperdrive** | Database pooling | `env.HYPERDRIVE.connectionString` |
45| **Rate Limiting** | Request throttling | `env.RATE_LIMITER.limit(id)` |
46| **Workflows** | Long-running workflows | `env.MY_WORKFLOW.create()` |
47 
48### Configuration Bindings
49 
50| Binding | Use Case | Access Pattern |
51|---------|----------|----------------|
52| **Environment Variables** | Non-sensitive config | `env.API_URL` (string) |
53| **Secrets** | Sensitive values | `env.API_KEY` (string) |
54| **Text/Data Blobs** | Static files | `env.MY_BLOB` (string) |
55| **WASM** | WebAssembly modules | `env.MY_WASM` (WebAssembly.Module) |
56 
57## Quick Selection Guide
58 
59**Need persistent storage?**
60- Key-value < 25MB → **KV**
61- Files/objects → **R2**
62- Relational data → **D1**
63- Real-time coordination → **Durable Objects**
64 
65**Need AI/compute?**
66- LLM inference → **Workers AI**
67- Scraping/PDFs → **Browser Rendering**
68- Call another Worker → **Service binding**
69 
70**Need async processing?**
71- Background jobs → **Queues**
72 
73**Need config?**
74- Public values → **Environment Variables**
75- Secrets → **Secrets** (never commit)
76 
77## Quick Start
78 
791. **Add binding to wrangler.jsonc:**
80```jsonc
81{
82  "kv_namespaces": [
83    { "binding": "MY_KV", "id": "your-kv-id" }
84  ]
85}
86```
87 
882. **Generate types:**
89```bash
90npx wrangler types
91```
92 
933. **Access in Worker:**
94```typescript
95export default {
96  async fetch(request, env, ctx) {
97    await env.MY_KV.put('key', 'value');
98    return new Response('OK');
99  }
100}
101```
102 
103## Type Safety
104 
105Bindings are fully typed via `wrangler types`. See [api.md](api.md) for details.
106 
107## Limits
108 
109- 64 bindings max per Worker (all types combined)
110- See [gotchas.md](gotchas.md) for per-binding limits
111 
112## Key Concepts
113 
114**Zero-overhead access:** Bindings compiled into Worker, no network calls to access
115**Type-safe:** Full TypeScript support via `wrangler types`
116**Per-environment:** Different IDs for dev/staging/production
117**Secrets vs Vars:** Secrets encrypted at rest, never in config files
118 
119## See Also
120 
121- [Cloudflare Docs: Bindings](https://developers.cloudflare.com/workers/runtime-apis/bindings/)
122- [Wrangler Configuration](https://developers.cloudflare.com/workers/wrangler/configuration/)
123