The fastest way to shrink an MP4 is to re-encode it at lower settings

An MP4 file takes up space because of three things: video resolution (1080p versus 720p), frame rate (how many images per second), and bitrate (how much data each second of video uses). Reducing any of these three makes the file smaller. The trade-off is visible — lower bitrate means grainier video, lower resolution means blurrier video, lower frame rate means choppier motion. Most people can shrink a file to half its original size by lowering bitrate alone, keeping resolution and frame rate the same.

You do this by re-encoding the video, which means reading the original file and writing a new one with different settings. This takes time — a 10-minute video might take 5 to 15 minutes to re-encode, depending on your computer and the settings you choose. Free tools like HandBrake (Windows, Mac, Linux) and FFmpeg (command-line, all platforms) do this without watermarks or limits. Paid tools like Adobe Premiere Pro or DaVinci Resolve offer more control but cost money or a subscription.

Key Takeaways

  • Bitrate is the easiest setting to lower — reducing it from 10 Mbps to 5 Mbps cuts file size roughly in half with visible but often acceptable quality loss.
  • HandBrake is free, works on Windows, Mac, and Linux, and includes presets for common devices so you do not have to guess at numbers.
  • Lowering resolution (1080p to 720p) or frame rate (60 fps to 30 fps) shrinks files more than bitrate alone but is more noticeable to viewers.
  • Re-encoding takes time — expect 5 to 15 minutes for a 10-minute video on a typical computer, longer on older machines.
  • If you only need to trim out sections or change the container format, you can shrink a file without re-encoding, which takes seconds instead of minutes.

Using HandBrake to re-encode with lower bitrate

Open HandBrake, click the folder icon to select your MP4 file, then look at the right side of the window. Under the "Video" tab, you will see a "Bitrate" field with a number in it — this is what the original file uses. Lower this number to shrink the output. Start by cutting it in half. If the original is 10 Mbps, try 5 Mbps. If it is 8 Mbps, try 4 Mbps.

Leave the resolution and frame rate alone unless you want to change them. The "Encoder" dropdown should say "H.264" or "H.265" — H.265 produces smaller files than H.264 at the same quality, but older devices may not play it. Once you have set the bitrate, click "Start Encode" at the top right. HandBrake will show you a progress bar. When it finishes, you will have a new MP4 file in the folder you chose.

Test the new file on the device or screen where you will actually watch it. If it looks acceptable, you are done. If it is too grainy, increase the bitrate by 1 or 2 Mbps and re-encode again. If it is still too large, lower it further or reduce the resolution instead.

Lowering resolution or frame rate for bigger file reductions

If lowering bitrate alone does not shrink the file enough, reduce the resolution. In HandBrake, under the "Dimensions" tab, you will see width and height. A 1920×1080 video (1080p) can become 1280×720 (720p). Click the chain link icon between width and height to keep the proportions correct — if you change one, the other adjusts automatically.

Lowering resolution from 1080p to 720p typically cuts file size by 40 to 50 percent. The video will look noticeably softer on a large screen, but on a phone or tablet it is often acceptable. For social media or web sharing, 720p is standard anyway.

Frame rate is less common to change. Most videos are 24, 30, or 60 frames per second. Lowering 60 fps to 30 fps cuts file size roughly in half but makes motion look choppy — only do this if the video is mostly still shots or text. In HandBrake, the frame rate setting is under the "Video" tab, labeled "Framerate".

Trimming sections instead of re-encoding the whole file

If your MP4 is large because it contains footage you do not need, trim it instead of re-encoding. This is much faster — it takes seconds instead of minutes — because you are not re-encoding, just removing sections and keeping the rest as-is.

In HandBrake, you cannot trim. Use FFmpeg from the command line, or use a free GUI tool like LosslessCut (Windows, Mac, Linux). LosslessCut lets you drag the video into the window, mark the start and end points of the section you want to keep, and click "Export". The file shrinks when ready because no re-encoding happens.

Trimming works best when you have clear sections to remove — a long intro, a failed take, credits at the end. If the entire video is content you want to keep, trimming will not help.

Changing the container format without re-encoding

An MP4 file is a container — it holds video and audio in a specific format. Sometimes the same video and audio can fit in a different container and take up less space. This is rare with MP4, but it is worth knowing about.

If you have an MP4 that contains H.264 video and AAC audio, converting it to a Matroska container (.mkv) might save a few percent, but the difference is small. Most of the time, the container format does not matter — the video and audio inside are what take up space.

If you want to try this anyway, use FFmpeg or HandBrake and set the output format to MKV instead of MP4. The re-encoding time is the same, but you might save 2 to 5 percent of file size. Whether that is worth the hassle depends on how much space you need to free up.

Comparing file size before and after re-encoding

Before you re-encode, write down the original file size. Right-click the MP4 file, select "Properties" (Windows) or "Get Info" (Mac), and look for "Size" or "File Size". Note the number in gigabytes or megabytes.

After re-encoding finishes, check the new file size the same way. Compare the two. If the new file is 50 percent smaller and looks acceptable, you have found a good balance. If it is only 10 percent smaller, the quality loss may not be worth it — try lowering the bitrate more or reducing resolution.

Keep the original file until you are sure the new one works. Once you have tested it on the device where you will watch it, you can delete the original to free up space.

When to use each tool for different situations

HandBrake is the best choice if you are new to video editing or want a straightforward interface. It has presets for common devices (iPhone, iPad, Android phone) that set bitrate, resolution, and frame rate automatically. You just pick your device and click "Start Encode". It works on Windows, Mac, and Linux.

FFmpeg is faster and more powerful but requires typing commands in a terminal. Use it if you are comfortable with command-line tools or need to process many files at once. It runs on Windows, Mac, and Linux.

LosslessCut is the right tool if you only want to trim sections out, not re-encode. It is fast and straightforward — drag, mark, export.

DaVinci Resolve or Adobe Premiere Pro are overkill for just shrinking a file, but if you are already editing the video in one of these programs, you can export it with lower bitrate settings instead of opening a separate tool.

Frequently Asked Questions

How much smaller can I make an MP4 without it looking terrible?

Most people can cut file size in half by lowering bitrate alone without noticing much difference on a phone or tablet. On a large monitor or TV, the loss becomes visible. Test on the actual screen where you will watch it. If you lower bitrate, resolution, and frame rate all together, you can cut file size to 25 percent of the original, but the video will look noticeably worse.

Does re-encoding damage the video quality?

Yes, slightly. Every time you re-encode, you lose a small amount of detail. If you re-encode the same file multiple times, the quality gets worse each time. Always keep the original file and re-encode from that, not from the already-compressed version.

Can I reduce file size without re-encoding?

Only if you trim out sections. Re-encoding is the only way to shrink a file while keeping the same length, because the video and audio data itself has to be compressed differently. Changing the container format (MP4 to MKV) saves almost nothing.

How long does re-encoding take?

A 10-minute video typically takes 5 to 15 minutes to re-encode on a modern computer, depending on the bitrate and resolution you choose. Older computers or laptops take longer. The progress bar in HandBrake shows you how much time is left.

What bitrate should I use?

Start with half the original bitrate and test it. If it looks good, you are done. If it is too grainy, increase it by 1 or 2 Mbps. For reference, YouTube recommends 8 Mbps for 1080p video, so anything above 5 Mbps at 1080p is usually acceptable for most viewers.