Cloudflare Bindings Skill Reference
Expert guidance on Cloudflare Workers Bindings - the runtime APIs that connect Workers to Cloudflare platform resources.
What Are Bindings?
Bindings 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.
Reading Order
- This file - Binding catalog and selection guide
- api.md - TypeScript types and env access patterns
- configuration.md - Complete wrangler.jsonc examples
- patterns.md - Best practices and common patterns
- gotchas.md - Critical pitfalls and troubleshooting
Binding Catalog
Storage Bindings
| Binding | Use Case | Access Pattern |
|---|---|---|
| KV | Key-value cache, CDN-backed reads | env.MY_KV.get(key) |
| R2 | Object storage (S3-compatible) | env.MY_BUCKET.get(key) |
| D1 | SQL database (SQLite) | env.DB.prepare(sql).all() |
| Durable Objects | Coordination, real-time state | env.MY_DO.get(id) |
| Vectorize | Vector embeddings search | env.VECTORIZE.query(vector) |
| Queues | Async message processing | env.MY_QUEUE.send(msg) |
Compute Bindings
| Binding | Use Case | Access Pattern |
|---|---|---|
| Service | Worker-to-Worker RPC | env.MY_SERVICE.fetch(req) |
| Workers AI | LLM inference | env.AI.run(model, input) |
| Browser Rendering | Headless Chrome | env.BROWSER.fetch(url) |
Platform Bindings
| Binding | Use Case | Access Pattern |
|---|---|---|
| Analytics Engine | Custom metrics | env.ANALYTICS.writeDataPoint(data) |
| mTLS | Client certificates | env.MY_CERT (string) |
| Hyperdrive | Database pooling | env.HYPERDRIVE.connectionString |
| Rate Limiting | Request throttling | env.RATE_LIMITER.limit(id) |
| Workflows | Long-running workflows | env.MY_WORKFLOW.create() |
Configuration Bindings
| Binding | Use Case | Access Pattern |
|---|---|---|
| Environment Variables | Non-sensitive config | env.API_URL (string) |
| Secrets | Sensitive values | env.API_KEY (string) |
| Text/Data Blobs | Static files | env.MY_BLOB (string) |
| WASM | WebAssembly modules | env.MY_WASM (WebAssembly.Module) |
Quick Selection Guide
Need persistent storage?
- Key-value < 25MB → KV
- Files/objects → R2
- Relational data → D1
- Real-time coordination → Durable Objects
Need AI/compute?
- LLM inference → Workers AI
- Scraping/PDFs → Browser Rendering
- Call another Worker → Service binding
Need async processing?
- Background jobs → Queues
Need config?
- Public values → Environment Variables
- Secrets → Secrets (never commit)
Quick Start
- Add binding to wrangler.jsonc:
{
"kv_namespaces": [
{ "binding": "MY_KV", "id": "your-kv-id" }
]
}- Generate types:
npx wrangler types- Access in Worker:
export default {
async fetch(request, env, ctx) {
await env.MY_KV.put('key', 'value');
return new Response('OK');
}
}Type Safety
Bindings are fully typed via wrangler types. See api.md for details.
Limits
- 64 bindings max per Worker (all types combined)
- See gotchas.md for per-binding limits
Key Concepts
Zero-overhead access: Bindings compiled into Worker, no network calls to access
Type-safe: Full TypeScript support via wrangler types
Per-environment: Different IDs for dev/staging/production
Secrets vs Vars: Secrets encrypted at rest, never in config files