Mobile data blocking interfering with open in browser (localhost) when not connected to wifi

[asl97]

I encountered an really weird edge case, so I thought about sharing and documenting it a little, since searching about the issue only brought out decade old results.

It was where opening localhost in browser didn't work, I thought it was specific to acode but after digging deeper, it also happens with server ran with termux.

I thought maybe it was something to do with DNS, maybe some browser settings/extension or some hidden proxy setting on android as mention on google, some 10+ years ago.

After hours of digging and trying stuff, it turns out to be the feature to block mobile data per app.

Some android vendor version has a feature to block mobile data per app, that causes even localhost to not work when not connected to a wifi network, the wifi network doesn't need to have internet access.

Screenrecorder-2025-06-25-13-46-11-57.mp4

video showing:

1. connected to internet-less wifi network
2. reload page - working
3. disable wifi
4. reload page - not working
5. turn off mobile data disabler
6. reload page - working

asl97/asl97.github.io#5

Hopefully the next person with this issue will have this post and/or related post shows up in their search and not spend hours figuring out why localhost isn't working in certain app when not connected to wifi.