Why Are iPhone Videos So Large? HEVC, HDR and 4K Explained

iPhones record at high resolution (often 4K), high frame rates and in HDR, which adds up to a lot of data per minute, even with the efficient HEVC codec. The videos also don't always play well elsewhere: HEVC isn't supported everywhere and HDR can look washed out on standard screens. Converting to 1080p or 720p H.264 MP4 makes them much smaller and playable everywhere.

Three settings that multiply the size

Resolution. 4K has four times the pixels of 1080p.
Frame rate. 60 frames per second carries about twice the motion data of 30.
HDR. High dynamic range video stores more colour and brightness information per pixel.

You can see the effect on your own phone: Settings → Camera → Record Video lists the approximate size of one minute of video for each option.

HEVC, H.264 and compatibility

With Settings → Camera → Formats set to High Efficiency (the default), iPhones record in HEVC (H.265), which is more efficient than the older H.264. The catch is support: some Windows PCs, older Android phones, smart TVs and websites don't play HEVC, or need an extra codec. "Most Compatible" records H.264 instead, at a larger size.

Why HDR video can look washed out

iPhone HDR video uses Dolby Vision/HLG. On a screen or app that doesn't understand HDR, it may look grey, washed out or oddly bright. Converting it to standard dynamic range (SDR) with proper tone mapping keeps colours natural everywhere.

How to make an iPhone video smaller

Get the original file onto your computer (AirDrop, the Files app or a cable). Some apps compress automatically when sharing, which can lower quality twice.
Open Compress MOV and choose the video.
Pick 1080p for viewing on large screens, 720p for phones and messaging.
Compress. The result is an H.264/AAC MP4, upright, in SDR, without location metadata.

For future recordings

If you mostly share clips in chats, recording at 1080p 30 fps instead of 4K 60 fps (Settings → Camera → Record Video) makes every file much smaller from the start. Keep 4K for footage you plan to edit.

Why are iPhone videos so large?