How to change browser User-Agent Header with javaScript?

Question

Following code changes property printed (when accessed through javaScript) by browser console and not the actual Use-Agent string sent with the header.

Object.defineProperty(navigator, 'userAgent', {
    get: function () { return 'Mozilla/5.0 (Windows NT 6.2; WOW64; 
    rv:28.0) Gecko/20100101 Firefox/28.0)'; }
});

A Navigator object can be retrieved using the read-only window.navigator property. developer.mozilla.org/en-US/docs/Web/API/Navigator — mplungjan
– mplungjan, Commented Sep 19, 2019 at 7:44
Firefox and Safari just let you use XHR.setRequestHeader('User-Agent', 'whatever'). Chrome on the other hand throws an error... — Kaiido
– Kaiido, Commented Sep 19, 2019 at 12:19

Gertjan Brouwer · Accepted Answer · 2020-12-27 19:54:06Z

5

This is now possible to do, see: https://developer.mozilla.org/en-US/docs/Glossary/Forbidden_header_name You can use ‘ XMLHttpRequest.setRequestHeader(User-Agent, value)’

answered Dec 27, 2020 at 19:54

Gertjan Brouwer

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2 Comments

gimlichael Over a year ago

Although it should be possible, it does seems like Chromium is behaving like old IE - they make there own rules. I tested both Chrome and Edge - User-Agent is being ignored and controlled by said browsers.

gimlichael Over a year ago

Chromium responds with this in the console: Refused to set unsafe header "User-Agent".

Brad · Accepted Answer · 2019-09-19 07:37:00Z

3

This isn't possible from the page itself. The user agent string (as sent in the HTTP request headers) can only be changed via browser extension or browser configuration.

answered Sep 19, 2019 at 7:37

Brad

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1 Comment

user435421 Over a year ago

I trust you are right but maybe you could provide a link to so something that confirms your statement

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