MDN’s new design is in Beta! A sneak peek:

The bodyUsed read-only property of the Body mixin contains a Boolean that indicates whether the body has been read yet.


var myBodyUsed = response.bodyUsed;


A Boolean.


In our fetch request example (run fetch request live), we create a new request using the Request.Request constructor, then use it to fetch a JPG. When the fetch is successful, we read a Blob out of the response using blob(), put it into an object URL using URL.createObjectURL, and then set that URL as the source of an <img> element to display the image.

Notice that we log response.bodyUsed to the console once before the response.blob() call and once after. This returns false before and true afterwards, as at that point the body has been read.

HTML Content

<img class="my-image" src="">

JS Content

var myImage = document.querySelector('.my-image');
fetch('').then(function(response) {
    var res = response.blob();
    return res;
}).then(function(response) {
    var objectURL = URL.createObjectURL(response);
    myImage.src = objectURL;


Specification Status Comment
The definition of 'bodyUsed' in that specification.
Living Standard  

Browser compatibility

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 42 [1]
(Yes) 39 (39) [2] No support

29 [3]

No support
Feature Android Edge Firefox Mobile (Gecko) Firefox OS (Gecko) IE Phone Opera Mobile Safari Mobile Chrome for Android
Basic support No support (Yes) No support No support No support No support No support No support

[1] Behind a preference in version 41.

[2] Behind a preference starting with version 34.

[3] Behind a preference in version 28.

See also

Document Tags and Contributors

 Contributors to this page: chrisdavidmills, Hugues-Antoine, erikadoyle, fscholz, kscarfone
 Last updated by: chrisdavidmills,