How to Reduce Video File Size on iPhone

On this page, 9 sections

A minute of video from a modern iPhone is a genuinely large file. Large enough that email bounces it, large enough that a chat app quietly re-encodes it into something that looks worse than what you shot, large enough that a hundred of them fill a phone. And unlike photos, where the sizes are small enough to ignore, video size is a problem you meet every single time you try to send something.

There are four levers here and most people only know about one of them. Worth going through all four, because two of them cost you nothing in quality and one of them is a setting you change once and never think about again.

Where the size actually comes from

Three numbers multiply together: how many pixels are in each frame, how many frames there are per second, and how many bits the encoder spends describing each of them.

4K has roughly four times the pixels of 1080p. Sixty frames per second is twice as many frames as thirty. Stack those and a 4K sixty clip is many times the size of a 1080p thirty clip of the same length, and on a phone screen you will struggle to tell them apart.

You can see Apple’s own figures for this. Go to Settings, Camera, Record Video and each option lists an approximate size per minute underneath it. Read those numbers on your own phone rather than trusting anyone’s article, including mine, because they vary by model. The gap between the top and bottom of that list is dramatic.

Lever one: trim, which costs nothing

Deleting frames is free. Compressing frames is not. So always trim before you compress.

1. Open the video in Photos.
2. Tap Edit.
3. Drag the yellow handles at either end of the filmstrip inward.
4. Tap Done, then choose Save Video as New Clip if you want to keep the original.

Every video I shoot has two seconds of nothing at the start and three of me reaching for the button at the end. Cutting those off a fifteen second clip removes a third of the file for zero quality cost. The full detail, including how to revert a trim later, is in trimming a video on iPhone without an app.

Lever two: compress it properly

Once the length is right, compression is the tool. This is where Grabio lives, and it is the reason I built the thing in the first place. Share the video, tap Grabio, choose Compress, pick a level, save the result.

It sits in the iOS share sheet, so you reach it from Photos, from Files, from a chat, from anywhere a video can be shared. No App Store install, no account, no paid tier.

[NEED: screenshot of the Grabio compress options screen]

How hard to compress depends entirely on where the video is going, and the useful targets differ a lot between platforms. I wrote separate walkthroughs with the actual limits for the common destinations: WhatsApp, email, Discord, and Instagram. Aiming at the specific limit beats guessing, because compressing far below what a platform allows is throwing away quality for nothing.

Lever three: let Mail do it, when Mail is the destination

This one is built in and almost nobody uses it. Attach a video to an email in the Mail app and, before sending, iOS offers you a choice of sizes: Small, Medium, Large and Actual Size. Picking a smaller one re-encodes the attachment on the way out and leaves your original untouched.

It is crude, there is no fine control, and the smallest setting is genuinely small. For sending a clip to a relative it is completely sufficient and it takes one tap. If the recipient needs the good version, that is what the other levers are for.

Lever four: change the setting so this stops happening

Two settings decide how big your future videos are.

Settings, Camera, Record Video. If you are shooting at 4K sixty and posting to Instagram, you are recording several times the data you will ever use. 1080p at thirty frames per second is enough for anything that ends up on a phone screen, and the file sizes are a different order of magnitude. Change it back for the things that genuinely deserve 4K.

Settings, Camera, Formats. High Efficiency uses HEVC, which produces meaningfully smaller files at the same quality. Most Compatible uses the older H.264, which every device on earth can play. If you regularly send video to people on old Windows machines, compatibility is worth the size. Otherwise High Efficiency is the sensible default.

Neither of these helps with video you already shot. Both of them stop the problem repeating.

If you only wanted the audio, stop compressing

Worth checking before you spend effort. If the reason you have a big video is that someone gave a talk, or you recorded a rehearsal, or you want a voice note out of it, the audio alone is a tiny fraction of the size and it is a two tap job.

Share the video, run Extract Audio, and you are done. Details in extracting audio from a video on iPhone. An hour of audio is smaller than a minute of 4K, so this is the largest reduction available anywhere in this article, when it applies.

The same logic runs the other way for very short clips. A three second reaction shot works better as a GIF in a chat, covered in converting a video to GIF on iPhone. Be aware that GIF is inefficient and the size climbs fast past a few seconds.

When compression is the wrong answer entirely

There is a point where squeezing a file to fit an attachment limit does so much damage that you should stop. A twenty minute 4K video is never going to be an email attachment that anyone enjoys watching.

At that point, send a link instead. iCloud Drive, Google Drive, Dropbox, or Apple’s Mail Drop, which handles large attachments by uploading them and sending a link automatically. The options and their limits are in sending a large video file from an iPhone. The recipient gets the real quality and your inbox does not fight you.

What compression actually costs you

Being honest about the trade: compression works by throwing away information the encoder guesses you will not miss. At mild settings that guess is very good. At aggressive settings you start seeing blocking in dark areas, smearing on fast motion, and a general softness in fine detail like hair and grass.

Two rules keep this manageable. Compress from the original file rather than from something you already compressed, because the damage accumulates. And compress to the size you actually need instead of the smallest possible, because there is no prize for going under the limit.

If you want the tools two taps away in the share sheet, Get the Shortcut. Free, no login, no upgrade prompt, because there is nothing to upgrade to.

Frequently asked questions

Why are iPhone videos so large?

Because the default recording settings favour quality over size, often 4K at a high frame rate. Pixels multiplied by frames multiplied by bitrate produces a big number very quickly. Settings, Camera, Record Video shows the approximate size per minute for each option on your specific model.

Does trimming a video reduce its file size?

Yes, and it is the only method that costs no quality at all, because you are removing frames rather than degrading them. Trim first, then compress if the file is still too big. Choosing Save Video as New Clip keeps the original intact in your library.

How much can I compress a video before it looks bad?

It depends on the footage. Static scenes survive heavy compression well, while fast motion, dark scenes and fine detail fall apart much sooner. Compress to the size the destination actually requires rather than to the smallest possible, and always work from the original rather than from an already compressed copy.

Is there a free video compressor for iPhone?

Yes. Grabio is a free iOS Shortcut with a Compress tool that runs from the share sheet, with no App Store install and no account. Apple’s Mail app also offers size options when you attach a video, which is enough for casual sending.

Should I record in 1080p or 4K?

1080p at thirty frames per second is plenty for anything that will be watched on a phone or posted to social media, and the files are far smaller. Use 4K when you plan to crop heavily, edit properly, or view on a large screen. You can change the setting per situation in the Camera settings.

What is the difference between High Efficiency and Most Compatible?

High Efficiency records HEVC, which produces smaller files at the same visual quality. Most Compatible records H.264, which plays on virtually anything including older Windows machines. Pick compatibility only if you regularly hand files to people on old hardware.