1# Cloudflare Snippets Skill Reference
2 
3## Description
4Expert guidance for **Cloudflare Snippets ONLY** - a lightweight JavaScript-based edge logic platform for modifying HTTP requests and responses. Snippets run as part of the Ruleset Engine and are included at no additional cost on paid plans (Pro, Business, Enterprise).
5 
6## What Are Snippets?
7Snippets are JavaScript functions executed at the edge as part of Cloudflare's Ruleset Engine. Key characteristics:
8- **Execution time**: 5ms CPU limit per request
9- **Size limit**: 32KB per snippet
10- **Runtime**: V8 isolate (subset of Workers APIs)
11- **Subrequests**: 2-5 fetch calls depending on plan
12- **Cost**: Included with Pro/Business/Enterprise plans
13 
14## Snippets vs Workers Decision Matrix
15 
16| Factor | Choose Snippets If... | Choose Workers If... |
17|--------|----------------------|---------------------|
18| **Complexity** | Simple request/response modifications | Complex business logic, routing, middleware |
19| **Execution time** | <5ms sufficient | Need >5ms or variable time |
20| **Subrequests** | 2-5 fetch calls sufficient | Need >5 subrequests or complex orchestration |
21| **Code size** | <32KB sufficient | Need >32KB or npm dependencies |
22| **Cost** | Want zero additional cost | Can afford $5/mo + usage |
23| **APIs** | Need basic fetch, headers, URL | Need KV, D1, R2, Durable Objects, cron triggers |
24| **Deployment** | Need rule-based triggers | Want custom routing logic |
25 
26**Rule of thumb**: Use Snippets for modifications, Workers for applications.
27 
28## Execution Model
291. Request arrives at Cloudflare edge
302. Ruleset Engine evaluates snippet rules (filter expressions)
313. If rule matches, snippet executes within 5ms limit
324. Modified request/response continues through pipeline
335. Response returned to client
34 
35Snippets execute synchronously in the request path - performance is critical.
36 
37## Reading Order
381. **[configuration.md](configuration.md)** - Start here: setup, deployment methods (Dashboard/API/Terraform)
392. **[api.md](api.md)** - Core APIs: Request, Response, headers, `request.cf` properties
403. **[patterns.md](patterns.md)** - Real-world examples: geo-routing, A/B tests, security headers
414. **[gotchas.md](gotchas.md)** - Troubleshooting: common errors, performance tips, API limitations
42 
43## In This Reference
44 
45- **[configuration.md](configuration.md)** - Setup, deployment, configuration
46- **[api.md](api.md)** - API endpoints, methods, interfaces
47- **[patterns.md](patterns.md)** - Common patterns, use cases, examples
48- **[gotchas.md](gotchas.md)** - Troubleshooting, best practices, limitations
49 
50## Quick Start
51```javascript
52// Snippet: Add security headers
53export default {
54  async fetch(request) {
55    const response = await fetch(request);
56    const newResponse = new Response(response.body, response);
57    newResponse.headers.set("X-Frame-Options", "DENY");
58    newResponse.headers.set("X-Content-Type-Options", "nosniff");
59    return newResponse;
60  }
61}
62```
63 
64Deploy via Dashboard (Rules → Snippets) or API/Terraform. See configuration.md for details.
65 
66## See Also
67 
68- [Cloudflare Docs](https://developers.cloudflare.com/rules/snippets/)
69