Yeah. MV3 is a faster but less capable version.

With MV2, every request must be filtered with slow, JIT, garbage-collected JavaScript code. In MV3, filtering is handled by native browser code using the list provided by extensions. UserScripts could be used to modify the DOM, but that requires power users to manually enable it.

There is a limit on how large the list can be, depending on the browser.

JavaScript really isn't that slow. JIT compilation can wind up faster than AOT compilation. And much of the APIs called by JavaScript is natively-implemented browser code. JavaScript is faster than C# yet people implement games in C# (not the engine cores, but that's a very similar situation to JS) and don't bat an eye.

> JavaScript is faster than C#

Are you joking? C# is in another leage, when we talk about performance.

> JavaScript is faster than C#

Apples to oranges, scripts need an entire browser/Interpeter framework underneath it to even function

See the mentioned game engine reference which closely parallels this.

I also thought under MV3 you could block ads, but not the tracking that they do.

But a list of like 100 domains will get rid of most major ad services.

that is theoretically true. but i switched to the v3-compatible ublock origin lite a year ago and i've noticed essentially no difference in the performance. all the ads are blocked, just like they were with the v2-compatible adblocker.