How to compress 1GB video to 10MB without losing too much quality?

10MB for a 12-minute 1080p video is extremely restrictive, so some noticeable quality loss is unavoidable. The most important factor here is the bitrate, not just the compression setting.

For a 12-minute video, 10MB gives you roughly 110 kbps total bitrate, including audio. I’d consider reducing the resolution to around 480p or even 360p, using 24–30 fps, and allocating most of the bitrate to the video by keeping audio around 24–32 kbps.

If the upload limit is strict, use a two-pass encode and set the target file size/bitrate rather than relying on a generic “compress” preset. H.265/HEVC or AV1 can also provide better quality at very low bitrates than older codecs, although compatibility may be an issue.

At 10MB, though, I’d first check whether the platform offers a larger limit or accepts a lower-resolution version—10MB is simply too small to retain 1080p quality for 12 minutes.