Compress videos on your iPhone to save storage

What compression actually does

Shrinking a video means decoding it and encoding it again at a lower bitrate or a smaller frame size. The result is a new file. It is smaller because information has been discarded, and that information does not come back. This is a real trade, not a free optimisation, and any app that presents it as free is glossing over the important half.

For most phone video the trade is a good one. A clip shot at 4K that you will only ever watch on a phone screen or send to someone loses very little that you would notice at 720p, and it can shrink dramatically. For footage you might edit, print a frame from, or watch on a television, it is a bad trade and you should leave it alone.

How Nixly does it

Nixly lists videos of 50 MB or more, sorted biggest first, each with its measured file size and duration. When you shrink one:

1. Nixly exports a 720p MP4 on the device using Apple's AVFoundation framework. Nothing is uploaded to a server for processing.
2. It measures the real size of the file that came out.
3. It saves the smaller copy into your photo library.
4. Only once that save has succeeded does it remove the original, which goes to Recently Deleted like any other deletion and can be recovered for 30 days.
5. The saving it reports is the difference between the two actual files.

If the export does not come out smaller than the original, Nixly does nothing. Your video is left exactly as it was. This matters because a video already encoded efficiently at a modest bitrate can come out of a re-encode larger, and an app that swaps the files regardless would cost you space and picture quality at the same time.

When shrinking is worth it

• Long 4K clips you will watch on a phone. The biggest wins by a distance.
• Screen recordings. Often long, often huge, rarely worth their original quality.
• Videos you keep for the memory, not the picture. A birthday clip is about who is in it.

When it is not

• Anything you might edit later. Editing a re-encoded file compounds the quality loss.
• Short clips. A 60 MB video saves you 60 MB at most and usually far less. Deleting one you do not want is a better use of the same minute.
• Footage for a big screen. 720p is visibly soft on a television.
• Anything irreplaceable at full quality. Copy it off the phone first.

The free alternatives

You do not need an app to reduce video storage. Two things help and cost nothing:

• Record smaller going forward. Settings > Camera > Record Video lets you choose a lower resolution or frame rate. This does nothing for existing footage but stops the problem growing.
• Move the originals off the phone. Copying to a computer or a drive keeps full quality and frees the whole file, which beats any compression ratio.

Simply deleting the videos you will never watch again is also, boringly, the most effective option available. Nixly's large video list exists to make that decision easy: it puts the biggest files in front of you with their real sizes, so a few taps can be worth more than an hour of compressing.

What it costs

Video shrinking is part of Nixly Pro, which is 4.99 US dollars per week with a 3 day free trial, or 29.99 US dollars per year without one. The scan that shows you the video list, its sizes and the total is free, so you can see whether there is anything worth shrinking before you decide.