Guide 03 · 4 min read

Compress a video on iPhone without losing quality

Phone video is big because of bitrate, not pixels. Lower the bitrate sensibly and a file shrinks by half or more with no difference you can see on a phone screen.

Why the file is so large

A minute of 4K at 60 frames per second from a recent iPhone is around 400 MB. Most of that is bitrate: the amount of data the camera allows per second of video. Resolution matters less than people think; a 1080p video at a high bitrate can be larger than a 4K one at a low bitrate.

Three things decide the size: resolution (4K or 1080p), frame rate (24, 30 or 60) and bitrate. The codec matters too: HEVC (H.265) files are roughly 40% smaller than H.264 at the same quality, and every iPhone since the 7 records HEVC by default.

Settings that stop videos being huge in the first place

  • Settings → Camera → Record Video: 1080p at 30 fps is plenty for messaging, social posts and family videos. Keep 4K for footage you will edit or watch on a TV.
  • Settings → Camera → Formats → High Efficiency: this is HEVC. "Most Compatible" doubles file sizes.
  • Turn off Auto FPS and 60 fps unless you need slow motion.

Compressing videos you already have

Photos has no compressor. Sending through Messages or Mail reduces size but you do not control how much, and the original stays full size. MediaSlim does this on the phone, with the original untouched until you choose to replace it:

  1. Open MediaSlim, choose Compress Video and pick one or more videos.
  2. Keep the resolution; lower the quality one step. For a phone screen, a bitrate of 8 to 12 Mbps for 1080p and 20 to 30 Mbps for 4K is indistinguishable from the original.
  3. Check the preview and the new size, then save. The compressed copy appears in Photos next to the original.
  4. When you are happy, delete the original (and empty Recently Deleted to free the space).

What "without losing quality" really means

Every re-encode loses something. The point is to lose what no screen can show. Keep the resolution and frame rate, keep HEVC, and reduce bitrate moderately. Avoid compressing the same file twice; go back to the original if you want a smaller version later.

Photos and PDFs too

The same app converts HEIC photos to JPG for people who cannot open HEIC, shrinks photos for forms and email, and compresses PDFs. It also removes hidden metadata (location, device, time) before you share a file.

Questions

Will compressing a video make it blurry?
Not at moderate settings. Blur and blocking appear only when the bitrate is pushed far below what the resolution needs. Keep the resolution and lower quality one step at a time.
Why is my video still large after AirDrop?
AirDrop sends the original file. Compress first, then share the smaller copy.
Does this work on iPad?
Yes. MediaSlim runs on iPhone and iPad.

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