Guide
Why is my video file so big?
The short answer
File size is bitrate multiplied by duration, and bitrate is driven by resolution, frame rate and how much movement there is. A minute of 4K at 60fps can be 400 MB; the same minute at 1080p30 might be 60 MB with no visible difference on a phone.
By FixMyFiles Updated How we write these
The four numbers
Resolution. 4K has four times the pixels of 1080p, and roughly four times as much to encode. Dropping from 4K to 1080p is the single largest saving available, and on a phone screen it is invisible.
Frame rate. 60fps is twice the frames of 30fps. Worth keeping for genuine motion — sport, gaming — and wasted on a talking head or a screen recording.
Bitrate. How many bits per second the encoder is allowed. This is the number that actually sets file size; everything else influences how much bitrate the video needs to look acceptable.
Movement. A static screen recording compresses to almost nothing because successive frames barely differ. Handheld footage of leaves in wind is the opposite: every pixel changes every frame, and the encoder has to describe all of it.
What to change first
In order of how much you save per unit of quality lost: reduce the resolution, then the frame rate if the content does not need it, then the bitrate, and only then reach for a more efficient codec.
Cutting the parts you do not need is often better than all of them. Thirty seconds trimmed off a two-minute clip is a quarter of the file gone with no quality cost at all, and Trim Video can often do it without re-encoding.
Audio is rarely the problem. A whole hour of good AAC audio is about 60 MB, next to nothing beside the picture.
When there is a specific limit
Working backwards from the target is the only reliable approach: the size you need and the length of the clip together determine the bitrate you can afford, and the quality follows from that.
Compress Video takes the limit — 25 MB for Gmail, 16 MB for WhatsApp, 20 MB on a free Discord account — and finds settings that land under it. Every upload limit we know lists the numbers.
If it still will not fit, the clip is too long for the limit. Trim it or split it rather than compressing it into mush.
Questions
Does lowering resolution reduce file size a lot?
Yes, more than any other single change. Going from 4K to 1080p typically cuts the file to around a quarter.
Is it better to lower bitrate or resolution?
Resolution, usually. A clean 1080p file looks better than a 4K file starved of bitrate, because the encoder is not forced to smear detail it cannot afford.
Why is my screen recording so large?
Usually a high frame rate and a high-resolution display, sometimes with a lossless codec. Screen content compresses extremely well once the frame rate comes down.