FIX THIS ****. IM NOT PAYING FOR YOUR ******* TWITCH PRIME OR WHATEVER YOU ARE TRYING TO SELL BY NOT FIXING THIS. SORRY FOR CAPS, I HAVE TO YELL OVER THE ADS

This has been a problem for me for years. It is the one thing that drives me away from Twitch for periods at a time. It's an AWFUL viewing experience. Though considering I've been following/posting on a different uservoice thread about this for like 4 years - which was replied to by staff who falsely stated it was fixed - I'm not holding my breath that anyone at Twitch actually gives af about the viewing experience lol

Does the volume control slider actually go up, or do ads just sound louder?

Historically, TV channels made rules about how loud ads could be. Advertisers responded by using clever dynamic range tricks to make ads sound louder to humans even though they were technically the same volume. Eventually, Congress banned this. You can read more at https://en.wikipedia.org/wiki/Commercial_Advertisement_Loudness_Mitigation_Act

However, this law doesn't apply to the internet. And I don't know if platforms like Twitch even have rules for advertisers about peak amplitude, meaning advertisers could just make their ads louder without affecting your volume settings. California specifically passed a law to extend CALM to the internet, but this doesn't take effect until 2026-7-1. Even then, I suspect that Twitch won't apply this to users outside of California, even though Twitch's offices are in California; it will probably only apply to ads served within California.

I realize that's a lot of words, but the important point is: Is this a bug with the Twitch web app, or a problem with Twitch's advertisers and the rules it sets for them? Twitch will need to know this in order to be able to fix the problem.

Personally, I almost never see ads on Twitch, so I don't have direct experience to answer this question myself. But you probably can.