A Firefox user agent switcher changes the browser and system details your browser reports to websites, so you can see how a site behaves for a different browser or device. Two listings are large and the rest are small, and some share a name, so check the author line. Nine follow in no particular order.
Developers, testers and SEO people use a user agent switcher to check what a site serves to a different browser or device without switching machines. Search Firefox's add-on site for one and you'll get a long list of near-identical names, most with only a few hundred daily users.
I've listed nine alphabetically and in no particular order. Every number comes from each add-on's Firefox Add-ons (addons.mozilla.org) listing: author, daily users, average rating, ratings count, last updated date and the Recommended badge, as of Oct 2026. If you're on the other side of this and want to keep bots off your pages, my guide to stopping AI bots scraping your content is worth a read.
What I looked at and the nine in a table
Each add-on here says on its listing that it changes the user agent string. I read the same things on every listing: author, daily users, average rating, ratings count, last updated date and badge. Type and Good for come from each description. None of the nine says whether it's free, so the last column reads Not stated, as of Oct 2026.
| Tool | Type | Good for | Free plan |
|---|---|---|---|
| Change User-Agent | Single custom string | Setting one custom user agent permanently | Not stated |
| Custom UserAgent String | Per-site user agent | Custom strings for chosen URLs or domains | Not stated |
| Random User-Agent (Switcher) | Random rotation | Switching to a random user agent on a timer | Not stated |
| User Agent | Identity set with client hints | User agent, client hints and navigator properties together | Not stated |
| User Agent Switcher | Per-domain switcher | Custom user agent by domain | Not stated |
| User-Agent Switcher and Manager | Switcher and manager | Changing the browser and system details sites gather | Not stated |
| User-Agent Switcher and Manager Material | Switcher with a newer interface | The same spoofing job with a modern interface | Not stated |
| User-Agent Switcher by Linder | Preset switcher | Quick switching between popular user agent strings | Not stated |
| User-Agent Switcher by ntninja | String override | Overriding the browser's user agent string | Not stated |
Nine user agent switchers for Firefox
Change User-Agent
Best for: Setting one custom user agent string and leaving it in place, from a tiny listing with 95 daily users as of Oct 2026.
Custom UserAgent String
Best for: Giving chosen URLs or domains their own custom user agent string, from Linder, who also publishes another switcher on this list.
Random User-Agent (Switcher)
Best for: Rotating your user agent to a randomly selected one after a set time, which its listing says hides your real one.
User Agent
Best for: Changing the user agent, client hints and navigator properties together as one set, with per-site rules and a built-in detection check.
User Agent Switcher
Best for: A simple per-domain switcher from a listing last updated July 12, 2019, the oldest date on this list as of Oct 2026.
User-Agent Switcher and Manager
Best for: Presenting a different browser and operating system to sites that gather those details, from the only Recommended listing here.
User-Agent Switcher and Manager Material
Best for: People who like the same switching idea with a newer, modern looking interface, from a separate author.
User-Agent Switcher by Linder
Best for: Quick switching between a set of popular user agent strings, without typing your own.
User-Agent Switcher by ntninja
Best for: Overriding the user agent string in a few clicks, from a listing updated more recently than any other here, as of Oct 2026.
Two big listings, a thin tail and names that repeat
Only one listing here carries Mozilla's Recommended by Firefox badge, and it has 85,437 daily users. Every other switcher on this list is under 63,000, and five of the nine are under 1,000, as of Oct 2026. The smallest has 95 daily users.
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Names repeat, too. Two separate add-ons are both listed as User-Agent Switcher, one by Linder and one by ntninja, and a third takes the Recommended add-on's name and adds Material to it under a different author. The author line is the only reliable way to tell them apart.
Averages need care here. Random User-Agent (Switcher) shows 241 ratings on 3,816 daily users, while one listing shows a perfect 5.0 from just 4 ratings, as of Oct 2026. The oldest last updated date on the list is July 12, 2019.
What you're switching for decides the add-on
- Testing how a site looks to another browser: pick a switcher with a set of preset strings.
- One custom string all the time: pick a single-string add-on and set it once.
- Different strings for different sites: pick one with per-site or per-domain rules.
- Not looking like the same visitor every time: pick one that rotates to a random string on a timer.
- Client hints as well as the string: pick one whose listing names client hints and navigator properties.
Before you trust a switcher
- Read the author line, since several names here start the same way.
- Check the last updated date. On this list it runs from July 12, 2019 to October 26, 2026, as of Oct 2026.
- Look at how many ratings sit behind the average.
- Switch back to your normal user agent when you're done, so sites don't keep serving you the wrong version.
If you're checking how pages render for search, my guide to choosing an SEO tool that improves rankings covers the tools built for that job.
Do you make a user agent switcher for Firefox? Tool makers can ask to be considered for a featured place on this list.
My plain advice on user agent switchers
Pick by the job, not the name. If you only need to test a site as a phone or another browser now and then, a switcher with presets is all you need. If you need rules per site or client hints, read the listing for those exact words. Then check the author line twice, because the same name can belong to three different people.
And don't leave a spoofed user agent running once you've finished testing. Sites will keep serving you the version you asked for, and that's confusing when you've forgotten it's on.
Want your tool on this list? Featured spots and reviews here are paid partnerships. Here's how to partner with me.
Frequently asked questions
What does a user agent switcher do in Firefox?
It changes the browser and operating system details Firefox reports to websites, so a site treats you as a different browser or device. Some listings here also add per-site rules or random rotation.
Why are there so many add-ons called User-Agent Switcher?
Different authors use the same name. On this list two separate add-ons share that exact name, so the author line on the listing is how you tell them apart.
Which user agent switcher has the most users on Firefox?
On this list the one with the most daily users has 85,437, and it's the only one with the Recommended by Firefox badge, as of Oct 2026.
Are Firefox user agent switchers free?
None of the nine listings here says either way, so this page marks them Not stated. Read each listing in full before you add one.
Can I set a different user agent for each website?
Yes. Several listings here say they support custom strings for chosen URLs, domains or per-site rules.
