WorkerGlobalScope: fetch() method

Baseline Widely available *

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨March 2017⁩.

* Some parts of this feature may have varying levels of support.

Note: This feature is only available in Web Workers.

The fetch() method of the WorkerGlobalScope interface starts the process of fetching a resource from the network, returning a promise that is fulfilled once the response is available.

The promise resolves to the Response object representing the response to your request.

A fetch() promise only rejects when the request fails, for example, because of a badly-formed request URL or a network error. A fetch() promise does not reject if the server responds with HTTP status codes that indicate errors (404, 504, etc.). Instead, a then() handler must check the Response.ok and/or Response.status properties.

The fetch() method is controlled by the connect-src directive of Content Security Policy rather than the directive of the resources it's retrieving.

Note: The fetch() method's parameters are identical to those of the Request() constructor.

Syntax

fetch(resource)
fetch(resource, options)

Parameters

resource

This defines the resource that you wish to fetch. This can either be:

A string or any other object with a stringifier — including a URL object — that provides the URL of the resource you want to fetch. The URL may be relative to the base URL, which is the document's baseURI in a window context, or WorkerGlobalScope.location in a worker context.
A Request object.

options Optional

A RequestInit object containing any custom settings that you want to apply to the request.

Return value

A Promise that resolves to a Response object.

Exceptions

AbortError DOMException: The request was aborted due to a call to the AbortController abort() method.
NotAllowedError DOMException: Thrown if use of the Topics API is specifically disallowed by a browsing-topics Permissions Policy, and a fetch() request was made with browsingTopics: true.
TypeError: An error when the fetch operation could not be performed. See Window.fetch() exceptions for a list of reasons why this error can occur.