Cloudflare Snippets Skill Reference

Description

Expert 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).

What Are Snippets?

Snippets are JavaScript functions executed at the edge as part of Cloudflare's Ruleset Engine. Key characteristics:

Execution time: 5ms CPU limit per request
Size limit: 32KB per snippet
Runtime: V8 isolate (subset of Workers APIs)
Subrequests: 2-5 fetch calls depending on plan
Cost: Included with Pro/Business/Enterprise plans

Snippets vs Workers Decision Matrix

Factor	Choose Snippets If...	Choose Workers If...
Complexity	Simple request/response modifications	Complex business logic, routing, middleware
Execution time	<5ms sufficient	Need >5ms or variable time
Subrequests	2-5 fetch calls sufficient	Need >5 subrequests or complex orchestration
Code size	<32KB sufficient	Need >32KB or npm dependencies
Cost	Want zero additional cost	Can afford $5/mo + usage
APIs	Need basic fetch, headers, URL	Need KV, D1, R2, Durable Objects, cron triggers
Deployment	Need rule-based triggers	Want custom routing logic

Rule of thumb: Use Snippets for modifications, Workers for applications.

Execution Model

Request arrives at Cloudflare edge
Ruleset Engine evaluates snippet rules (filter expressions)
If rule matches, snippet executes within 5ms limit
Modified request/response continues through pipeline
Response returned to client

Snippets execute synchronously in the request path - performance is critical.

Reading Order

configuration.md - Start here: setup, deployment methods (Dashboard/API/Terraform)
api.md - Core APIs: Request, Response, headers, request.cf properties
patterns.md - Real-world examples: geo-routing, A/B tests, security headers
gotchas.md - Troubleshooting: common errors, performance tips, API limitations

In This Reference

configuration.md - Setup, deployment, configuration
api.md - API endpoints, methods, interfaces
patterns.md - Common patterns, use cases, examples
gotchas.md - Troubleshooting, best practices, limitations

Quick Start

// Snippet: Add security headers
export default {
  async fetch(request) {
    const response = await fetch(request);
    const newResponse = new Response(response.body, response);
    newResponse.headers.set("X-Frame-Options", "DENY");
    newResponse.headers.set("X-Content-Type-Options", "nosniff");
    return newResponse;
  }
}

Deploy via Dashboard (Rules → Snippets) or API/Terraform. See configuration.md for details.

README.md