Fun fact: Opera had a tab functionality before Firefox. In fact a little-known browser called InternetWorks from the 90s is thought to be the first that had them.
If one thing will always be true on the internet, it will be forum posters saying "Opera had it first".
Firefox also had it when it was called Firebird, and I'm sure Mozilla had tabs.
I was an Opera user. They were the innovators in the browser space back in the day. Eventually it just felt too bloated, and sadly now they are essentially another Chromium fork.