openai/netlify-edge-functions

Netlify Edge Functions

Edge functions run on Netlify's globally distributed edge network (Deno runtime), providing low-latency responses close to users.

Syntax

import type { Config, Context } from "@netlify/edge-functions";

export default async (req: Request, context: Context) => {
  return new Response("Hello from the edge!");
};

export const config: Config = {
  path: "/hello",
};

Place files in netlify/edge-functions/. Uses .ts, .js, .tsx, or .jsx extensions.

Config Object

export const config: Config = {
  path: "/api/*",                    // URLPattern path(s)
  excludedPath: "/api/public/*",     // Exclusions
  method: ["GET", "POST"],           // HTTP methods
  onError: "bypass",                 // "fail" (default), "bypass", or "/error-page"
  cache: "manual",                   // Enable response caching
};

Middleware Pattern

Use context.next() to invoke the next handler in the chain and optionally modify the response:

export default async (req: Request, context: Context) => {
  // Before: modify request or short-circuit
  if (!isAuthenticated(req)) {
    return new Response("Unauthorized", { status: 401 });
  }

  // Continue to origin/next function
  const response = await context.next();

  // After: modify response
  response.headers.set("x-custom-header", "value");
  return response;
};

Return undefined to pass through without modification:

export default async (req: Request, context: Context) => {
  if (!shouldHandle(req)) return; // continues to next handler
  return new Response("Handled");
};

Geolocation and IP

export default async (req: Request, context: Context) => {
  const { city, country, subdivision, timezone } = context.geo;
  const ip = context.ip;

  if (country?.code === "DE") {
    return Response.redirect(new URL("/de", req.url));
  }
};

Local dev with mocked geo: netlify dev --geo=mock --country=US

Environment Variables

Use Netlify.env (not process.env or Deno.env):

const secret = Netlify.env.get("API_SECRET");

Module Support

• Node.js builtins: import { randomBytes } from "node:crypto";
• npm packages: Install via npm and import by name
• Deno modules: URL imports (e.g., import X from "https://esm.sh/package")

For URL imports, use an import map:

// import_map.json
{ "imports": { "html-rewriter": "https://ghuc.cc/worker-tools/html-rewriter/index.ts" } }

# netlify.toml
[functions]
  deno_import_map = "./import_map.json"

When to Use Edge vs Serverless

| Use Edge Functions for | Use Serverless Functions for | |---|---| | Low-latency responses | Long-running operations (up to 15 min) | | Request/response manipulation | Complex Node.js dependencies | | Geolocation-based logic | Database-heavy operations | | Auth checks and redirects | Background/scheduled tasks | | A/B testing, personalization | Tasks needing > 512 MB memory |

Limits

| Resource | Limit | |---|---| | CPU time | 50 ms per request | | Memory | 512 MB per deployed set | | Response header timeout | 40 seconds | | Code size | 20 MB compressed |