--- title: Scheduler description: Use the scheduler.wait() API to delay execution in Workers. image: https://developers.cloudflare.com/dev-products-preview.png --- > Documentation Index > Fetch the complete documentation index at: https://developers.cloudflare.com/workers/llms.txt > Use this file to discover all available pages before exploring further. [Skip to content](#%5Ftop) # Scheduler ## Background The `scheduler` global provides task scheduling APIs based on the [WICG Scheduling APIs proposal ↗](https://github.com/WICG/scheduling-apis). Workers currently implement the `scheduler.wait()` method. `scheduler.wait()` returns a Promise that resolves after a given number of milliseconds. It is an `await`\-able alternative to `setTimeout()` that does not require a callback. Like other [timers in Workers](https://developers.cloudflare.com/workers/runtime-apis/web-standards/#timers), `scheduler.wait()` does not advance during CPU execution when deployed to Cloudflare. This is a [security measure to mitigate against Spectre attacks](https://developers.cloudflare.com/workers/reference/security-model/#step-1-disallow-timers-and-multi-threading). In local development, timers advance regardless of whether I/O occurs. ## Syntax JavaScript ``` await scheduler.wait(delay);await scheduler.wait(delay, options); ``` ## Parameters * `delay` number * The number of milliseconds to wait before the returned Promise resolves. * `options` object optional * Optional configuration for the wait operation. * `signal` AbortSignal optional * An [AbortSignal](https://developers.cloudflare.com/workers/runtime-apis/web-standards/#abortcontroller-and-abortsignal) that cancels the wait. When the signal is aborted, the returned Promise rejects with an `AbortError`. ## Return value A `Promise` that resolves after `delay` milliseconds. If an `AbortSignal` is provided and aborted before the delay elapses, the Promise rejects with an `AbortError`. ## Examples ### Basic delay Use `scheduler.wait()` to pause execution for a specified duration. * [ JavaScript ](#tab-panel-12402) * [ TypeScript ](#tab-panel-12403) JavaScript ``` export default { async fetch(request) { // Wait for 1 second await scheduler.wait(1000); return new Response("Delayed response"); },}; ``` TypeScript ``` export default { async fetch(request): Promise { // Wait for 1 second await scheduler.wait(1000); return new Response("Delayed response"); },} satisfies ExportedHandler; ``` ### Retry with exponential backoff Use `scheduler.wait()` to implement a delay between retry attempts. This example uses exponential backoff with jitter. * [ JavaScript ](#tab-panel-12406) * [ TypeScript ](#tab-panel-12407) JavaScript ``` async function fetchWithRetry(url, maxAttempts = 3) { const baseBackoffMs = 100; const maxBackoffMs = 10000; for (let attempt = 0; attempt < maxAttempts; attempt++) { try { return await fetch(url); } catch (err) { if (attempt + 1 >= maxAttempts) { throw err; } const backoffMs = Math.min( maxBackoffMs, baseBackoffMs * Math.random() * Math.pow(2, attempt), ); await scheduler.wait(backoffMs); } } throw new Error("unreachable");} export default { async fetch(request) { const response = await fetchWithRetry("https://example.com/api"); return new Response(response.body, response); },}; ``` TypeScript ``` async function fetchWithRetry(url: string, maxAttempts = 3): Promise { const baseBackoffMs = 100; const maxBackoffMs = 10000; for (let attempt = 0; attempt < maxAttempts; attempt++) { try { return await fetch(url); } catch (err) { if (attempt + 1 >= maxAttempts) { throw err; } const backoffMs = Math.min( maxBackoffMs, baseBackoffMs * Math.random() * Math.pow(2, attempt), ); await scheduler.wait(backoffMs); } } throw new Error("unreachable");} export default { async fetch(request): Promise { const response = await fetchWithRetry("https://example.com/api"); return new Response(response.body, response); },} satisfies ExportedHandler; ``` ### Cancel with AbortSignal Use an [AbortController](https://developers.cloudflare.com/workers/runtime-apis/web-standards/#abortcontroller-and-abortsignal) to cancel a pending wait. * [ JavaScript ](#tab-panel-12404) * [ TypeScript ](#tab-panel-12405) JavaScript ``` export default { async fetch(request) { const controller = new AbortController(); // Cancel the wait after 500ms setTimeout(() => controller.abort(), 500); try { await scheduler.wait(5000, { signal: controller.signal }); return new Response("Wait completed"); } catch (err) { if (err instanceof DOMException && err.name === "AbortError") { return new Response("Wait was cancelled", { status: 408 }); } throw err; } },}; ``` TypeScript ``` export default { async fetch(request): Promise { const controller = new AbortController(); // Cancel the wait after 500ms setTimeout(() => controller.abort(), 500); try { await scheduler.wait(5000, { signal: controller.signal }); return new Response("Wait completed"); } catch (err) { if (err instanceof DOMException && err.name === "AbortError") { return new Response("Wait was cancelled", { status: 408 }); } throw err; } },} satisfies ExportedHandler; ``` ## Related resources * [Timers](https://developers.cloudflare.com/workers/runtime-apis/web-standards/#timers) — `setTimeout()` and `setInterval()` APIs * [Performance and timers](https://developers.cloudflare.com/workers/runtime-apis/performance/) — `performance.now()` and timer security behavior * [AbortController and AbortSignal](https://developers.cloudflare.com/workers/runtime-apis/web-standards/#abortcontroller-and-abortsignal) — cancel asynchronous operations * [WICG Scheduling APIs proposal ↗](https://github.com/WICG/scheduling-apis) — the specification this API is based on ```json {"@context":"https://schema.org","@type":"TechArticle","@id":"https://developers.cloudflare.com/workers/runtime-apis/scheduler/#page","headline":"Scheduler · Cloudflare Workers docs","description":"Use the scheduler.wait() API to delay execution in Workers.","url":"https://developers.cloudflare.com/workers/runtime-apis/scheduler/","inLanguage":"en","image":"https://developers.cloudflare.com/dev-products-preview.png","dateModified":"2026-04-23","publisher":{"@type":"Organization","name":"Cloudflare","url":"https://www.cloudflare.com/"},"isPartOf":{"@type":"WebSite","@id":"https://developers.cloudflare.com/#website","name":"Cloudflare Docs","url":"https://developers.cloudflare.com/"}} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/directory/","name":"Directory"}},{"@type":"ListItem","position":2,"item":{"@id":"/workers/","name":"Workers"}},{"@type":"ListItem","position":3,"item":{"@id":"/workers/runtime-apis/","name":"Runtime APIs"}},{"@type":"ListItem","position":4,"item":{"@id":"/workers/runtime-apis/scheduler/","name":"Scheduler"}}]} ```