I have looked and tried a few distros but am not happy with any of them. I tried MXlinux and Puppy Linux.
What I am looking for is one that will load onto a USB stick and not affect my room mate's laptop's Windows computer. It has to be fast booting and only need internet/browser ability. BTW, I have permission to use the laptop, but with the condition that there is no tracking or any changes to his system.

What specifically are you not happy with?

This is called "live USB" or "live distro" or similar, and pretty much any distro can do that. (Compare the Distrowatch list for live distros with the one for all distros - there are differences, but not very many).

So if you only care about the browser, what is wrong with MX or Puppy?

(If you find those distros slow booting, it's probably the hardware - make sure you're not using a USB 1 slot/stick?)

Just get them to create a limited user account on the Windows OS that is already installed... then put firefox portable on a usb memory stick and then you don't need to go to all that effort.

1 members found this post helpful.

Try EasyOS, but you need to borrow another Linux computer.

Because of you mate condition - you should not use its computer at all. From USB you have access to all files. Kernel always sees the hard drive - live systems usually have things which makes life easier - but it is not secure. Linuxes mount ntfs partitions usually as ntfs-3g file system - which gives open access to all files on ntfs partition without restrictions. So it is very easy accidentally damage ntfs file system running Linux. Particularly puppy's here are bad asses cause on puppy default user is root. The solution to protect hard drive is to switch it off at bios level. There is no way to assure nothings will happen. If running live system with mounted ntfs partition get stuck - hardware reset would be required - at the end it maybe not possible to even run Windows. So to keep good relation with your mate I strongly advice to resign from idea to use live system on the person computer.

Edit: Bug in JavaScript code may cause firefox hang. So even only internet browsing may cause system hang.

Edit: You may try to convince your mate to install VirtualBox on Windows and run Linux instance inside virtual machine. Much more secure.

The best I have tried that always worked well in the Live Environment and maintained persistence:

antiX
EasyOS
KNOPPIX

Easy ? Barry lives in a tent. Anticap built a pyramid. antiX rocks

AntiX, at the boot screens, you can choose that the distro does not automount any drives, it can also be loaded to ram, be made persistent, so that you can save files to the pendrive itself - but no live system will be particularly fast booting running from a pendrive over USB.

https://antixlinux.com/

1 members found this post helpful.

I see the antiX fan club has arrived, and the usual suspects at that!

While I could give you some warm and fuzzy "answer" like "MX Linux and toy Puppy Linux are far from the only Linux choices out there"; quite honestly... just take cynwulf's advice in post #3 and stick with Windows.

I think I have found what I am looking for. It is called Tails and appears to be very secure.

Tails provides the means to be more secure, but security is based on user actions too; running secure software is only the first step.

A downside to Tails is that onion routing (TOR) slows down network access, and it deliberately doesn't support persistence (so you can't save your preferences/accounts like others distros support).

If you're ok with those things then it's probably a valid choice, otherwise you might want to do some more research.

Tails is just for anonymous internet surfing. It is not to hide from computer of you colleague - but from computers all other the world. You asked wrong question.

Perhaps you are unaware that the A in Tails is for amnesic?

The very first header on the Tails About page: "Leave no trace on the computer"

Suggestion -- put Ventoy on, say, a 32GB USB stick and try each distro mentioned for yourself by loading the ISO onto the Ventoy partitionl.

Because it's a good distro!

However, I happen to be running Devuan just now.....