Edge Functions Examples / Long-running Edge Functions

Long-running Netlify Edge Functions

Edge Functions are limited to 50ms of CPU time, but this does not include time spent waiting or making network calls. As long as a function returns headers within 40 seconds it can run indefinitely. If you need to make API calls or perform other work that takes longer than this, you can return a stream from the function and write to it when you have the data.

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

export default (request: Request, context: Context) => {
  const body = new ReadableStream({
    async start(controller) {
      // this might be an API call or other slow external operation
      const response = await doSomethingSlow();
      controller.enqueue(new TextEncoder().encode(response));
  return new Response(body, {
    headers: {
      "Content-Type": "text/plain",

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Pro tip!

Need to send updates to the browser from a long-running edge function? Check out the server-sent events (SSE) example.

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What are Edge Functions?

Using JavaScript and TypeScript, Netlify Edge Functions give you the power to modify network requests to localize content, serve relevant ads, authenticate visitors, A/B test content, and much more! And this all happens at the Edge — directly from the worldwide location closest to each user.

To use Edge Functions on Netlify, add JavaScript or TypeScript files to an edge-functions directory in your project.

Learn more in the docs.

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