How to Reduce Video File Size

Large video files are slow to upload, fill up your phone and can be too big to send in a message. The good news: most videos can be made much smaller with only a small visible difference — if you change the right settings.

What decides the size of a video file

File size is roughly bitrate × duration. Bitrate is how much data is used for each second of video. Everything else on this list affects how much bitrate you need to keep the picture looking good.

1. Lower the bitrate (or quality setting)

This has the biggest effect. Many editors offer quality presets such as High, Medium and Low — these mostly change the bitrate. Try a medium setting first and compare it with the original on the screen where people will actually watch it.

2. Lower the resolution

A 4K video has four times as many pixels as 1080p. If your video will be watched on phones or in a social feed, 1080p (or 720p for very small files) is often enough.

3. Lower the frame rate if there is little motion

Talking-head videos, slideshows and tutorials usually look fine at 30 fps or even 24–25 fps. Keep 60 fps for gaming and fast sports footage where smooth motion matters.

4. Use a more efficient codec — carefully

Newer codecs such as H.265 (HEVC) and AV1 can produce smaller files than H.264 at similar quality. The trade-off is compatibility: some older devices, browsers and editors cannot play them. H.264 in an MP4 file remains the safest choice when you are not sure where the video will be played.

5. Cut what you do not need

Every second you remove saves space. Trimming dead air at the start and end is the easiest win — see How to Trim a Video Without Losing Quality. Audio matters less than people think: 128–192 kbps AAC is usually plenty for voice and music.

For advanced users: compress with FFmpeg

FFmpeg's H.264 encoder uses a CRF (constant rate factor) value instead of a fixed bitrate. Lower numbers mean higher quality and bigger files; 23 is the default and values around 18–28 are common.

ffmpeg -i input.mp4 -c:v libx264 -crf 23 -preset medium -c:a aac -b:a 128k output.mp4

Summary

• Lower the quality/bitrate setting first — it has the biggest effect.
• Match the resolution to where the video will be watched.
• Use 30 fps unless you need smooth fast motion.
• Stick with H.264 MP4 unless you know the newer codec is supported.
• Trim anything you do not need.