How to reduce MP4 file size
To reduce an MP4's file size, re-encode it at a lower bitrate: drop the resolution (1080p to 720p), choose a lower quality setting, lower the frame rate, trim the length or remove the audio. Resolution and length make the biggest difference, because size is roughly bitrate × length.
The MP4 Compressor does it in your browser without uploading the file. It shows an estimated size as you change the settings.
Why MP4 files are big
A video's size is its bitrate (bits per second) times its length:
size in MB = bitrate in Mbps × seconds ÷ 8
A video recorded at 10 megabits per second takes 10 × 60 ÷ 8 = 75 MB for every minute. Twice as long is twice as big. Higher resolution and frame rate need more bits to look as good, which is why phone and camera footage runs large.
| Bitrate | Per minute | 10 minutes |
|---|---|---|
| 20 Mbps | 150 MB | 1.5 GB |
| 10 Mbps | 75 MB | 750 MB |
| 5 Mbps | 37.5 MB | 375 MB |
| 2 Mbps | 15 MB | 150 MB |
| 1 Mbps | 7.5 MB | 75 MB |
1 MB is 1,000,000 bytes here, and the figures leave out the MP4 container's own overhead.
Which setting saves the most
| Setting | What changes |
|---|---|
| Resolution | Fewer pixels to encode. 720p (1280 × 720) is 921,600 pixels a frame, 44% of 1080p's 2,073,600. 480p (854 × 480) is 20%. |
| Quality | In the MP4 Compressor, Small uses about 40% less video data than Balanced, and High about 50% more. |
| Frame rate | 60 to 30 fps means half as many frames. Very low frame rates make motion look choppy. |
| Length | Trimming a clip in half halves its size at the same settings. |
| Audio | Small next to video: 128 kbps is 960,000 bytes, about 1 MB, a minute. Remove it if the clip doesn't need sound. |
If the video is already well compressed, re-encoding it at the same resolution can save little; the MP4 Compressor tells you when the result isn't smaller. Then lower the resolution or frame rate.
Step by step
- Open the MP4 in the MP4 Compressor. MOV and WebM work too, up to 500 MB.
- Choose a goal. Pick quality (High, Balanced or Small) or Fit a size, for a target such as 10 MB, 20 MB or 25 MB.
- Lower the resolution if you need it smaller still: 1080p, 720p, 480p or 360p. Frame rate and audio bitrate are there too.
- Check the estimate, press Compress, play the result, then download it.
The output is an H.264 MP4 with AAC audio (Opus in the few browsers that can't encode AAC).
Fit it under an email limit
Email has hard attachment limits:
| Service | Attachment limit | Over the limit |
|---|---|---|
| Gmail, personal account | 25 MB | Gmail turns the attachment into a Google Drive link |
| Gmail, work or school | Set by the admin | Ask your Google Workspace administrator |
| Outlook.com | 25 MB | Share from OneDrive instead, up to 2 GB |
The MP4 Compressor's Email preset aims for 20 MB, which stays under both. In that budget a one-minute video gets 20 × 8 ÷ 60 = 2.67 Mbps; a five-minute video gets 533 kbps, so let the tool pick a lower resolution.
Will it lose quality?
Some. Any re-encode throws away detail, and a long video squeezed into a small size looks blocky. To keep more: choose High quality, keep the resolution, or trim the video instead of squeezing it. To shrink more: lower the resolution first, then the quality.
Make it smaller with the free MP4 Compressor
- Open the MP4 Compressor and choose your MP4.
- Pick a quality or a target size, and a resolution.
- Check the estimate, compress and download.
Your video is compressed in your browser and never uploaded. No sign-up and no daily limit.
Open the MP4 CompressorFAQ
How can I make an MP4 file smaller?
Re-encode it at a lower bitrate. Lower the resolution (1080p to 720p has 44% of the pixels), pick a smaller quality setting, lower the frame rate, trim it or remove the audio.
What do I do if an MP4 file is too big to send?
Compress it to a target size under the limit, or send a link. Gmail turns attachments over 25 MB into a Google Drive link on personal accounts, and Outlook.com lets you share a file from OneDrive instead of attaching it.
How do I compress an MP4 so I can email it?
Use a target size under the email limit. Personal Gmail and Outlook.com both allow 25 MB attachments; the MP4 Compressor's Email preset aims for 20 MB to stay safely under.
How do I reduce MP4 file size on Windows 11?
Open the MP4 Compressor in your browser on Windows 11, choose the file and compress it. There's nothing to install, and the video stays on your PC.
Why is my compressed MP4 barely smaller?
The video was probably compressed well already. Re-encoding at the same resolution can't save much. Lower the resolution or frame rate, or choose Small quality.
How do I compress an MP4 for Discord?
Use a target size under Discord's limit, 20 MB on a free account. See how to compress a video for Discord.
Related
Sources
Each page below was read on 27 October 2026. The size and pixel figures are arithmetic. The Small, Balanced and High comparisons are the MP4 Compressor's own preset values, copied from the tool.
- Gmail Help, Send attachments with your Gmail message. Personal Gmail accounts can attach up to 25 MB; work and school limits are set by the Google Workspace administrator; anything over the limit is turned into a Google Drive link automatically.
- Microsoft Support, Sending limits in Outlook.com. "The attachment size limit for files is 25 MB", and OneDrive files can be shared up to 2 GB.