The fastest way to shrink an MP4 file is to re-encode it at a lower bitrate using free software like HandBrake or FFmpeg
An MP4 file's size comes almost entirely from its video bitrate — how much data the video uses per second. Reducing that bitrate shrinks the file without changing the length or resolution. A 2-hour movie at 8 Mbps (megabits per second) takes up roughly 7 GB; the same movie at 2 Mbps takes up roughly 1.75 GB. The trade-off is visible quality loss, but for most uses — sharing online, storing on a phone, uploading to social media — lower bitrates look acceptable.
The process is called re-encoding or transcoding. You feed your original MP4 into software that reads it, compresses the video data, and writes a new, smaller MP4. This takes time — usually several minutes to an hour depending on file length and your computer's speed — but it is the only way to meaningfully reduce size.
Key Takeaways
- HandBrake is the easiest free tool for most people; it has a graphical interface and presets for common devices like phones and tablets.
- Lowering the bitrate to 2–4 Mbps produces files small enough to email or upload quickly while remaining watchable on screens up to 1080p.
- Reducing resolution (from 1920×1080 to 1280×720, for example) cuts file size more aggressively than bitrate alone, but the video will look noticeably smaller on large screens.
- Changing the video codec from H.264 to H.265 (HEVC) can cut file size by 40–50% at the same quality, but not all devices play H.265 files.
- The fastest reduction comes from lowering both bitrate and resolution together, though this requires accepting visible quality loss.
Using HandBrake to re-encode your video
HandBrake is free software available for Windows, Mac, and Linux. read it from handbrake.fr. Open the program, click the folder icon to select your MP4 file, and HandBrake will load it and show you the current bitrate, resolution, and codec.
In the left sidebar under "Presets", choose a preset based on where you plan to watch the video. "Fast 1080p30" keeps the resolution at 1920×1080 but uses a moderate bitrate suitable for streaming. "Android" or "iPad" presets lower the resolution to fit smaller screens and reduce bitrate accordingly. Each preset is a starting point — you can adjust the settings afterward.
To manually control bitrate, look for the "Video" tab. Set the bitrate slider or enter a number directly. Start with 3000 kbps (3 Mbps) for 1080p video and 1500 kbps (1.5 Mbps) for 720p. Lower numbers mean smaller files but more visible quality loss. Click "Start Encode" and HandBrake will process the file, which may take 10 minutes to an hour depending on length and your computer's processor speed.
Lowering resolution to cut file size more aggressively
If you need a much smaller file and do not mind the video looking smaller on screen, reduce the resolution. The "Dimensions" tab in HandBrake lets you change width and height. Common reductions are 1920×1080 (1080p) down to 1280×720 (720p), or 1280×720 down to 854×480 (480p).
Halving the resolution cuts file size by roughly 75% at the same bitrate, because you are encoding one-quarter as many pixels per frame. A 1080p video at 5 Mbps might be 3.5 GB; the same video at 720p and 5 Mbps might be 900 MB. The trade-off is that the video will look noticeably pixelated or blurry on a large monitor or TV, though it remains acceptable on phones and tablets.
For videos you plan to watch only on a phone or share on social media, 720p at 2 Mbps is usually the right balance. For archival or viewing on a computer, keep 1080p but lower the bitrate to 3–4 Mbps.
Choosing between H.264 and H.265 codecs
The codec is the compression method the video uses. Most MP4 files use H.264 (also called AVC), which nearly all devices play. H.265 (also called HEVC) is newer and compresses roughly 40–50% more efficiently, meaning you get the same quality at half the bitrate — or the same file size at much better quality.
The catch is compatibility. Older phones, tablets, and computers may not play H.265 files. iPhones from iPhone 7 onward support it. Most Android phones from 2017 onward support it. Windows 10 and 11 support it, but older versions do not. If you are sharing video with others or storing it for long-term use, H.264 is safer.
If you control where the video will be watched — for example, uploading to your own website or storing on your own devices — H.265 is worth using. In HandBrake, the "Video Codec" dropdown lets you choose. Select "H.265" and use a bitrate 40–50% lower than you would with H.264 to get similar quality.
Using FFmpeg from the command line for batch processing
If you have many videos to compress, or want more control than HandBrake offers, FFmpeg is a free command-line tool available for Windows, Mac, and Linux. read it from ffmpeg.org. The learning curve is steeper, but FFmpeg is faster and more flexible.
A basic command to re-encode an MP4 looks like this: ffmpeg -i input.mp4 -c:v libx264 -b:v 3000k output.mp4. This reads input.mp4, uses the H.264 codec, sets bitrate to 3000 kbps, and writes output.mp4. To use H.265 instead, replace libx264 with libx265. To change resolution, add -vf scale=1280:720 before the output filename.
FFmpeg processes files in the background without a graphical interface, which makes it ideal if you want to compress 50 videos overnight. You can also write a script to explore the same settings to an entire folder. Learning FFmpeg takes time, but it is the standard tool professionals use for video compression.
Comparing file size reduction across different methods
| Method | File Size Reduction | Quality Loss | Time to Encode |
|---|---|---|---|
| Lower bitrate only (5 Mbps to 2 Mbps) | 60% | Slight, visible on large screens | 10–30 minutes |
| Lower resolution only (1080p to 720p) | 75% | Noticeable, video looks smaller | 10–30 minutes |
| Lower bitrate + resolution (5 Mbps, 1080p to 2 Mbps, 720p) | 85% | Moderate, acceptable for phones | 10–30 minutes |
| Switch to H.265 codec (same bitrate and resolution) | 40–50% | None, quality stays the same | 20–60 minutes |
| H.265 + lower bitrate (5 Mbps to 2.5 Mbps) | 75% | Minimal, similar to H.264 at 5 Mbps | 20–60 minutes |
What not to do: avoiding common mistakes
Do not try to shrink an MP4 by straightforward deleting frames or cutting out sections using a video editor unless you actually want a shorter video. Editors that do this are not compressing — they are removing content. If you want the full video but smaller, re-encoding is the only method that works.
Do not re-encode an already-compressed file multiple times. Each re-encode introduces quality loss. If you compress a video to 2 Mbps, then compress that result again to 1 Mbps, the second compression starts with already-degraded video and produces worse results than compressing the original once to 1 Mbps. Always start from your original file.
Do not assume a lower bitrate will work for your use case without testing. read or export a small sample (the first 30 seconds) at your target bitrate, watch it on the device where it will actually be viewed, and confirm the quality is acceptable before processing the entire file.
Frequently Asked Questions
How much smaller can I make an MP4 without it looking terrible?
Most people find 2–3 Mbps acceptable for 1080p video on phones and tablets, and 3–5 Mbps acceptable on computer monitors. Below 1.5 Mbps, compression artifacts (blocky or blurry areas) become obvious. Test your target bitrate on the actual device where you will watch it before committing to the full file.
Will reducing file size affect the audio?
Not unless you change the audio codec or bitrate separately. By default, HandBrake and FFmpeg keep the audio unchanged. If you want to reduce audio bitrate too (which saves only a small amount), you can set it to 128 kbps or lower, though this may introduce noticeable quality loss in music or dialogue.
Can I undo a re-encode if the quality is too low?
No. Once you re-encode, the original data is gone from that file. Always keep your original MP4 before compressing. If the compressed version is unacceptable, delete it and re-encode the original at a higher bitrate.
Why does my re-encoded video play in some apps but not others?
This usually means the device or app does not support the codec you chose. If you used H.265 and the device is older, try re-encoding with H.264 instead. If the issue persists, the device may not support the resolution or frame rate — try lowering resolution to 720p and re-encoding.
How long does re-encoding take?
A 2-hour video typically takes 15–45 minutes on a modern computer, depending on the bitrate, resolution, codec, and your processor speed. Older computers or lower bitrates take longer. FFmpeg is usually faster than HandBrake by 10–20% because it uses fewer graphical elements.