I'm having the same issue. I tend to play my music quite low, then a deafening advert comes on which resets it to 100%, so I lower it's volume, then the next song the volume is reset again to 100%. I like having eardrums spotify.
That's weird, I haven't encountered that issue myself.
The Spotify volume slider jumps back at max when an ad comes along?
I don't know if clearing cache and cookies would help, but it's worth trying anyway.
A workaround that should function is opening the Mixer (on Taskbar click the Speaker icon and choose Mixer), slide the browser volume slider to the max and then lower the device volume slider to the level that's acceptable. Leave Spotify volume slider to max as well.
Spotify ain't able to tinker with the system volume level. 😉
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Somehow the Spotify player is actually screwing with my Windows volume. If I pause the music for a few minutes then come back and resume playing, Windows somehow has my volume at full. When I open up Mixer (actually using EarTrumpet since it gives better control) it shows both Spotify's and Windows' volume sliders being where I set them, but when I nudge the overall volume slider by 1 in either direction it gets quieter.
This is killing me because it somehow winds up causing the problem with all of my other applications. Pause Spotify for a few minutes and an email comes in? Outlook is blasting at 100% volume in my headphones. Close out Spotify and it doesn't happen.