XMLHttpRequest API
Baseline Widely available *
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
* Some parts of this feature may have varying levels of support.
Note: This feature is available in Web Workers, except for Service Workers.
The XMLHttpRequest API enables web apps to make HTTP requests to web servers and receive the responses programmatically using JavaScript. This in turn enables a website to update just part of a page with data from the server, rather than having to navigate to a whole new page. This practice is also sometimes known as AJAX.
The Fetch API is the more flexible and powerful replacement for the XMLHttpRequest API. The Fetch API uses promises instead of events to handle asynchronous responses, integrates well with service workers, and supports advanced aspects of HTTP such as CORS. For these reasons, the Fetch API is usually used in modern web apps instead of XMLHttpRequest
.
Concepts and usage
The central interface in the XMLHttpRequest API is XMLHttpRequest
. To make an HTTP request:
- Create a new
XMLHttpRequest
instance by calling its constructor. - Initialize it by calling
XMLHttpRequest.open()
. At this point you provide the URL for the request, the HTTP method to use, and optionally, a username and password. - Attach event handlers to get the result of the request. For example, the
load
event is fired when the request has successfully completed, and theerror
event is fired in various error conditions. - Send the request by calling
XMLHttpRequest.send()
.
For an in-depth guide to the XMLHttpRequest API, see Using XMLHttpRequest.
Interfaces
FormData
-
An object representing
<form>
fields and their values, which can be sent to a server usingXMLHttpRequest
orfetch()
. ProgressEvent
-
A subclass of
Event
which is passed into theprogress
, and which contains information about how much of the request has been completed. XMLHttpRequest
-
Represents a single HTTP request.
XMLHttpRequestEventTarget
-
A superclass of both
XMLHttpRequest
andXMLHttpRequestUpload
, defining the events that are available in both of those interfaces. XMLHttpRequestUpload
-
Represents the upload process for an HTTP upload. Provides events enabling code to track the progress of an upload.
Examples
Fetching JSON data from the server
In this example we fetch a JSON file from https://raw.githubusercontent.com/mdn/content/main/files/en-us/_wikihistory.json
, adding event listeners to show the progress of the event.
HTML
<div class="controls">
<button class="xhr" type="button">Click to start XHR</button>
</div>
<textarea readonly class="event-log"></textarea>
JavaScript
const xhrButton = document.querySelector(".xhr");
const log = document.querySelector(".event-log");
const url =
"https://raw.githubusercontent.com/mdn/content/main/files/en-us/_wikihistory.json";
function handleEvent(e) {
log.textContent = `${log.textContent}${e.type}: ${e.loaded} bytes transferred\n`;
}
function addListeners(xhr) {
xhr.addEventListener("loadstart", handleEvent);
xhr.addEventListener("load", handleEvent);
xhr.addEventListener("loadend", handleEvent);
xhr.addEventListener("progress", handleEvent);
xhr.addEventListener("error", handleEvent);
xhr.addEventListener("abort", handleEvent);
}
xhrButton.addEventListener("click", () => {
log.textContent = "";
const xhr = new XMLHttpRequest();
xhr.open("GET", url);
addListeners(xhr);
xhr.send();
});
Result
Specifications
Specification |
---|
XMLHttpRequest |
Browser compatibility
Report problems with this compatibility data on GitHubdesktop | mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
XMLHttpRequest | ||||||||||||
XMLHttpRequest() constructor | ||||||||||||
abort | ||||||||||||
abort event | ||||||||||||
Authorization header removed from cross-origin redirects | ||||||||||||
error event | ||||||||||||
getAllResponseHeaders | ||||||||||||
Header names returned in all lower case | ||||||||||||
getResponseHeader | ||||||||||||
load event | ||||||||||||
loadend event | ||||||||||||
loadstart event | ||||||||||||
open | ||||||||||||
overrideMimeType | ||||||||||||
progress event | ||||||||||||
readyState | ||||||||||||
readystatechange event | ||||||||||||
response | ||||||||||||
responseText | ||||||||||||
responseType | ||||||||||||
responseType.arraybuffer_value | ||||||||||||
responseType.blob_value | ||||||||||||
responseType.document_value | ||||||||||||
responseType.json_value | ||||||||||||
responseURL | ||||||||||||
responseXML | ||||||||||||
send | ||||||||||||
ArrayBufferView as parameter to send() | ||||||||||||
ArrayBuffer as parameter to send() | ||||||||||||
Blob as parameter to send() | ||||||||||||
FormData as parameter to send() | ||||||||||||
URLSearchParams as parameter to send() | ||||||||||||
setAttributionReporting | ||||||||||||
setPrivateToken | ||||||||||||
setRequestHeader | ||||||||||||
status | ||||||||||||
statusText | ||||||||||||
timeout | ||||||||||||
timeout event | ||||||||||||
upload | ||||||||||||
withCredentials | ||||||||||||
Available in workers |
Legend
Tip: you can click/tap on a cell for more information.
- Full support
- Full support
- Partial support
- Partial support
- No support
- No support
- Experimental. Expect behavior to change in the future.
- See implementation notes.
- Has more compatibility info.