I currently use an Android smartphone. Android 11 updated with MIUI 12 with 4G network.
The default youtube app consumes more data. Watching a few videos consumes more than 1 GB of data.
Is there any app that consumes less data?
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While the biggest part certainly depends on the video (and especially the video quality/resolution), the official YT app also consumes bandwidth for ads and such. So maybe you want to take a look at Newpipe, which is a free/libre open-source alternative to that. You won't find such clients on Google Play (as they do not meet the Play Store guidelines) – but then, F-Droid is a much safer place for apps anyway.
Make sure to chose a video resolution that's not too big (see the dropdown in the first screenshot: 720p is smaller than 1080p – and depending on your screen size, smaller ones like 480p would be fully sufficient, saving you bandwidth without you noticing a drop in quality). You can browse images as you're used to, see second screenshot. And as a bonus, you can even download videos – a feature the official app is unlikely to offer.
Newpipe is, as pointed out, free/libre and open source, so you can get it for free – no payment involved (though the author will certainly accept donations), no ads, no tracking. I can highly recommend the app. And F-Droid itself: use their app to keep Newpipe (and other apps from F-Droid) updated on your device.
Disclosure: while not being affiliated with Newpipe, I'm one of the F-Droid maintainers.