How to Reduce Size of Video on iPhone
On this page, 10 sections
A minute of 4K video at 60 frames per second from an iPhone is roughly 400 MB. Three minutes of your kid’s school play is over a gigabyte. That file will not attach to an email, will not clear a 100 MB upload form, and will take an uncomfortable amount of time to send over anything except good wifi.
So you open Photos looking for a compress button. There is not one. That is the honest starting point, and it is worth saying before anything else because half the frustration in this task comes from hunting for a feature that does not exist.
What follows is the full set of levers, in the order I would pull them.
Lever one: trim, because it is free
Duration is a direct multiplier on file size. Cut a third of the length and you cut roughly a third of the file. What makes trimming special is that it costs nothing in quality, since it removes whole frames and leaves the remaining ones bit for bit identical.
Open the clip in Photos, tap Edit, drag the yellow handles at either end of the filmstrip, tap Done, and choose Save Video as New Clip. That last choice matters. Picking Save Video overwrites the original, and picking Save Video as New Clip keeps both.
Almost every phone video has dead weight at both ends. Three seconds of you raising the phone. Four seconds at the end while your thumb finds the stop button. A stretch in the middle where nothing happens. Cut them first, then measure again, because very often the trim alone gets you under the limit and you can stop reading. The full walkthrough is at trimming a video on iPhone without an app.
Lever two: resolution, which is the big one
Resolution is the pixel count in each frame, and it scales as an area. 4K is 3840 by 2160. 1080p is 1920 by 1080. Halving each dimension quarters the number of pixels, which is why the 4K to 1080p step removes so much data before the codec has done anything clever.
Here is the part worth internalising. On a phone screen, on a laptop screen, and on most televisions people actually own, 1080p and 4K are hard to tell apart for handheld footage. The 4K advantage shows up when you crop in during editing, or on a very large display, or with a locked-off camera and good light. For a clip going into a chat window, 4K is storing detail that nobody will ever see.
720p is my default for anything that will be watched on a phone. 480p is the floor, visibly soft on a laptop and acceptable on a phone when a hard limit leaves no choice.
Lever three: frame rate
60 frames per second stores twice as much per second as 30. If you shot deliberately at 60 for slow motion or fast action, keep it. If your camera happened to be set that way and you are filming a person talking, dropping to 30 is a straightforward halving of the data rate with no meaningful loss.
This one is easy to forget because iOS does not show you the frame rate anywhere obvious in Photos. Save the clip to Files, long press, tap Get Info, and the details are there.
Lever four: motion, which you cannot change afterwards
This is the factor nobody thinks about and it explains a lot of confusing results.
Video codecs store what changed between frames rather than every frame from scratch. A locked-off shot of somebody talking against a plain wall compresses beautifully, because most of the picture is identical frame to frame. A handheld pan across a busy street changes every pixel in every frame and compresses badly.
The practical consequence is that two clips with identical resolution, frame rate and duration can differ in size by several times. If your compressed file is still too big, motion is usually why, and the fix is to trim harder or drop another resolution step rather than to assume the compression failed.
For next time: brace the phone, or lean on something. Steadier footage is smaller footage.
Actually doing the compression
iOS has no way to re-encode an existing video at a lower resolution. No option in Photos, nothing in Files, no Apple share sheet action. Apple’s Shortcuts app can do it, and building that workflow yourself is possible and fiddly, which is why I packaged it as a free Shortcut.
Open the video in Photos or Files, tap Share, scroll the share sheet and tap Grabio. Choose Compress from the menu, pick how far down you want to go, and the result comes back through the share sheet. Save to Files when it is heading for an upload form or a computer, save to Photos when you want it in your library. The original stays untouched either way.
[NEED: screenshot of the Grabio video menu with the compression options visible]
Grabio is free with no account and no paid version, and it installs into Apple’s Shortcuts app rather than from the App Store.
Know the number you are aiming at
Compressing without a target is how people end up doing it three times. The common ceilings:
- Email is usually about 25 MB for the whole message, and some corporate mail servers stop at 10 MB.
- Discord free tier allows 10 MB, which is the tightest limit most people meet.
- WhatsApp caps video attachments and compresses whatever you send, aggressively. Compressing sensibly yourself first usually produces a better looking result than letting WhatsApp decide. See the video compressor walkthrough.
- Instagram and other social apps care about aspect ratio and duration as much as size, and re-encode everything on upload regardless.
- Upload forms vary from 5 MB to 500 MB and rarely tell you until you have waited for the upload to fail.
The email case in particular has a specific guide at compressing a video for email on iPhone.
Sometimes the right answer is to not send the file
Worth naming, because it saves a lot of pointless compression. If the destination will accept a link, sending a link keeps full quality and takes seconds.
In Apple Mail, attaching a large video triggers Mail Drop, which uploads the file to iCloud and sends a download link that stays live for 30 days. In Photos, tapping Share and choosing Copy iCloud Link does the same thing for any clip. Neither costs you quality and neither needs the recipient to have an iPhone.
These routes and their limits are covered at sending a large video file from an iPhone. They are useless when a form wants the file itself, and perfect when a human just needs to watch something.
If you only need part of what is in the file
Two shortcuts that get overlooked.
If the value is in the sound rather than the picture, pull the audio out and send that instead. An audio file is a fraction of the size of the video it came from, and the process is quick. See extracting audio from a video on iPhone.
If you need to show a short moving moment rather than play a video, a GIF or a still frame may be all the recipient needs. Converting a video to GIF on iPhone covers the first, and a screenshot taken while the video is paused covers the second.
Stop generating gigabyte files in the first place
If this is a recurring problem, change the camera and it largely goes away.
Go to Settings, then Camera, then Record Video, and choose 1080p HD at 30 fps. Apple shows the storage cost per minute right there under each option, which makes the trade obvious. Switch up to 4K deliberately when you are filming something that deserves it, then switch back.
Also in Settings, then Camera, then Formats, High Efficiency records in HEVC and produces noticeably smaller files than Most Compatible, which records H.264. HEVC is harder for older computers and some websites to handle, so pick based on where your videos usually end up.
Get the Shortcut if you need the compression step iOS leaves out. Free, no account, and it lives in your share sheet.
Frequently asked questions
Can I compress a video on iPhone without an app?
Trimming in Photos reduces size with no quality loss and is entirely native. Re-encoding at a lower resolution is not something iOS offers anywhere, so it needs a Shortcut or a third party app. A Shortcut avoids the App Store install.
Does compressing a video reduce its quality?
Yes, re-encoding always discards information. Whether you notice depends on the screen. 4K down to 1080p is close to invisible on a phone or laptop. Below 480p most people can see it clearly, so treat that as the floor.
Why is my iPhone video so large?
Default recording on many iPhones is 4K at a high frame rate, which stores an enormous amount of data per second. Around 400 MB per minute at 4K 60 is normal. Changing Settings, Camera, Record Video to 1080p at 30fps cuts future recordings dramatically.
What is the difference between trimming and compressing?
Trimming removes seconds and leaves the remaining frames identical to the original, so there is no quality cost. Compressing re-encodes every frame at a lower resolution or quality. Trim first, then compress only if you still need to.
Will compressing fix a video that will not play on Windows?
Only if the format changes too. A file rejected for being HEVC or MOV needs converting rather than shrinking. Choosing an MP4 output while compressing handles both problems in one pass.
How do I check the size of a video on iPhone?
Share it to the Files app, then long press the file and tap Get Info. That shows the real size, the dimensions and the duration. The Photos app hides this, which is why so many people are guessing.