It supports both, and they've switched back and forth on what the default should be. They also supported duktape in the past.
I always use v8, because it has better compatibility with libraries and tools.
Re:The State of Linux Debuggers
by bretthoerner on Sunday December 13, 2020 @12:58PM
(#25408497)
Might be a case of outdated documentation/website: https://frida.re/news/2019/05/15/frida-12-5-released/
Interesting, it looks like there was a move from V8 to QuickJS more recently than that: https://frida.re/news/2020/10/28/frida-14-0-released/
EDIT: and then the default moved back in https://frida.re/news/2020/12/01/frida-14-1-released/
> Frida’s core is written in C and injects QuickJS into the target processes, where your JS gets executed with full access to memory, hooking functions and even calling native functions inside the process.
https://frida.re/docs/home/