Fetch Api vs Xmlhttprequest

Maya Lin-Takahashi
Maya Lin-Takahashi
• • 3 min read

I Know That Fetch Api Uses Promises and Both of Them Allow You to Do Ajax Requests to a Server. I Have Read That Fetch Api Has Some Extra Features, Which...

Fetch Api vs Xmlhttprequest

I know that Fetch API uses Promises and both of them allow you to do AJAX requests to a server.

I have read that Fetch API has some extra features, which aren't available in XMLHttpRequest (and in the Fetch API polyfill, since it's based on XHR).

What extra capabilities does the Fetch API have?

7

3 Answers

There are a few things that you can do with fetch and not with XHR:

  • You can use the Cache API with the request and response objects;
  • You can perform no-cors requests, getting a response from a server that doesn't implement CORS. You can't access the response body directly from JavaScript, but you can use it with other APIs (e.g. the Cache API);
  • Streaming responses (with XHR the entire response is buffered in memory, with fetch you will be able to access the low-level stream). This isn't available yet in all browsers, but will be soon.

There are a couple of things that you can do with XHR that you can't do yet with fetch, but they're going to be available sooner or later (read the "Future improvements" paragraph here: ):

  • Abort a request (this now works in Firefox and Edge, as @sideshowbarker explains in his comment);
  • Report progress.

This article contains a more detailed description.

6

Must Read

fetch

  • missing a builtin method to consume documents
  • no way to set a timeout yet
  • can't override the content-type response header
  • if the content-length response header is present but not exposed, the body's total length is unknown during the streaming
  • will call the signal's abort handler even if the request has been completed
  • no upload progress (support for ReadableStream instances as request bodies is yet to come)
  • doesn't support --allow-file-access-from-files (chromium)
Maya Lin-Takahashi

Maya Lin-Takahashi

Consumer Tech & Gadget Reviewer
Youtube Instagram Twitter

Maya is a hardware enthusiast who tests and reviews smart home devices, smartphones, wearables, and audio gear. She focuses on practical consumer value and build quality.