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How-To Guide

How to Compress an MP4 Video

MP4 video files can grow large — 4K footage easily exceeds 1 GB per minute. Compressing MP4 reduces file size for email, social media uploads, or storage. The right compression preserves quality while shrinking the file 50–80%. Three main techniques: lower CRF (more compression), reduce bitrate, or downscale resolution.

Open MP4 to MP4 Converter

Step-by-step instructions

  1. 1

    Upload your MP4 file

    Select your .mp4 file. The compressor analyses the video to suggest optimal settings — typically CRF, target bitrate, or resolution change.

    Go to converter
  2. 2

    Choose compression level

    Light: CRF 22, same resolution — typical 30% size reduction. Medium: CRF 26, 720p downscale — typical 60% reduction. Strong: CRF 30, 480p downscale — typical 80% reduction. Quality decreases progressively.

  3. 3

    Download and verify

    Compare file size and visual quality. Most viewers can't tell CRF 23 from the source on phones; CRF 28 is fine for casual viewing; below CRF 28 starts becoming visibly degraded.

Why convert MP4 to MP4?

Compressing MP4 is the daily task of sharing video — getting from camera-original size to upload-acceptable size while preserving viewing quality.

Your files never leave your device

FormatDrop runs the conversion engine entirely inside your browser using WebAssembly. No file upload. No server. Nothing stored. You can verify this by opening DevTools → Network tab and watching: zero upload requests.

Frequently asked questions

FFmpeg command to compress MP4?
`ffmpeg -i input.mp4 -c:v libx264 -crf 24 -preset slow -c:a aac -b:a 128k output.mp4`. CRF 18 = visually lossless, CRF 23 = default, CRF 28 = fairly compressed but watchable. Lower CRF = better quality, larger file.
What's the difference between CRF and bitrate compression?
CRF (Constant Rate Factor) is quality-based — encoder uses bits where needed to maintain perceptual quality, varying bitrate per scene. Bitrate is fixed — predictable file size but inconsistent quality. CRF is better for typical use; bitrate is better when targeting a specific file size.
How do I downscale resolution?
Add `-vf scale=-2:720` (720p, height) or `-vf scale=1280:-2` (1280px width, height auto). Combined with CRF: `ffmpeg -i input.mp4 -vf scale=-2:720 -c:v libx264 -crf 23 -c:a aac output.mp4`.
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