The free savings, in order
Cut the length. Nothing about the remaining footage changes, and the saving is exactly proportional. Trim Video cuts on keyframes where it can, which copies the stream through untouched.
Match the resolution to the destination. A clip for WhatsApp or Instagram is watched on a phone; 1080p is generous and 720p is often indistinguishable. Resize Video handles it.
Drop the frame rate when the content is static. A 60fps screen recording of someone typing carries no information a 30fps version lacks.
Mute it if the sound is not needed. Mute Video copies the picture untouched and simply drops the audio track.
The part that does cost something
Lowering bitrate is where quality actually goes. Encoders spend their allowance on what changes most, so as it tightens you first lose fine texture, then see blocking in dark areas and smearing around fast movement.
Push the codec before pushing the bitrate. The same visible quality in HEVC or AV1 needs meaningfully fewer bits than in H.264 — just make sure the person receiving it can play the result, which is the whole argument in H.264 vs H.265 vs AV1.
Encode from the best source you have, once. Compressing an already-compressed export stacks two rounds of loss, and that is what makes videos look bad far more often than any single setting.
Settings that work
For sharing a phone clip: 1080p, 30fps, H.264, and a bitrate around 4–6 Mbps. That is visually clean and comfortably small.
For a screen recording: keep the full resolution so text stays readable, drop to 30fps, and let the bitrate fall — static content needs very little.
For a specific size limit, do not guess. Compress Video takes the number and works out the rest, on your own device, without uploading a file that may be a gigabyte.