What's inside a Live Photo: two files and one identifier

A Live Photo is two files that Photos shows as one item: a still image (HEIC or JPEG) and a short QuickTime movie with sound. Both carry the same content identifier, and the movie has a marker for the frame that matches the still. Photos pairs them by that identifier, not by file name.

Below is what each file holds, how the pairing works, and what happens when the two are split up. To make your own from a video, Beavery builds both halves for you.

Two files, one item

Apple’s capture documentation says it directly: Photos shows a Live Photo as a single item, but it is made of separate files, the primary still image and a movie file with the motion and sound from just before and after. An app saves both into Photos together as one item.

The Photos framework describes the same thing from the library side. A Live Photo asset holds a still photo resource and a video resource; the video comes back as the paired video resource type. When you take one with the iPhone camera, Apple says the movie covers about 1.5 seconds before and after the shot. A Live Photo made from a video in an app such as Beavery covers whatever stretch you chose.

What we found in one

We saved a Live Photo from Beavery into the photo library of an iPhone simulator (the steps are here) and read the two files Photos stored for it. They sat side by side with the same name, IMG_0082.HEIC and IMG_0082.MOV.

Both files carried the same UUID. The movie side is documented: AVFoundation names the key quickTimeMetadataContentIdentifier. On the image side Apple documents the MakerApple dictionary but not the individual key that holds the identifier, so we only report what we saw in this file.

How Photos knows they belong together

The matching identifier is what pairs them. Apple’s documentation for loading a Live Photo from files says Photos can only build one “from the same set of files exported from a previously captured Live Photo asset”, and that it validates the files and their metadata first. If the check fails, there is no Live Photo, only the still.

So the file names do not matter, and neither does keeping the two files in the same folder. What matters is that both files still carry the identifier and that the movie was not re-encoded in a way that dropped its metadata.

Taking one apart and putting it back

On a Mac, Photos can export a Live Photo with File › Export › Export Unmodified Original; Apple says it comes out as two separate files, a still image and a video. To get them back into Photos as one Live Photo, an app has to add both files in one request (Apple’s PHAssetCreationRequest); dropping the two files into Photos one by one is not the documented way.

Beavery saves to Photos with that single request. When you export a Live Photo from Beavery to a folder instead, it writes one .beaverylive package that holds the still, the movie (motion.mov) and a small manifest, so the pair stays together and Beavery can open it again later.

What happens when you send one

Only some of this is documented by Apple:

• Mail sends a Live Photo as a still image.
• Messages on iPhone or iPad keeps it live: the person taps it, then presses and holds to play it. Messages on a Mac plays it once when opened.
• Sharing only the still is a choice in the share sheet: tap LIVE in the upper-left corner of the photo before you pick where to send it.

For other apps (chat apps, social networks, cloud drives) Apple’s documentation cannot tell you the answer. It depends on the receiving app: an app that keeps both files and their metadata can show the motion, while an app that keeps or recompresses only the picture shows a still. Channel-by-channel advice is in why a Live Photo stops moving after sending.

When the two files come apart

• It went through a channel that sends only the still, such as Mail.
• The receiving app kept the picture and dropped the movie.
• Live was turned off: in Photos you can switch a Live Photo to Off, which makes it a still.
• It was edited elsewhere. Apple notes that editing a Live Photo in another app can lose its Live Photo effects.
• The two files were separated and changed, so their identifiers or metadata no longer match.

If you are making Live Photos from your own videos, save them to Photos and send them from Photos. That keeps both halves together for as long as the channel allows. For fixes, see Live Photo not moving after sending; for what the movie keeps in quality and HDR, see video to Live Photo quality. Beavery for Mac saves Live Photos the same way.

Questions

Is a Live Photo just a short video?

No. It is a full still photo plus a separate short movie. Photos shows the still and plays the movie when you press and hold. The still is not a frame grabbed from the movie at viewing time; it is its own file.

Can I email a Live Photo?

Apple says a Live Photo shared through Mail is sent as a still image. Messages between Apple devices keeps it live; for other apps it depends on the receiving app.

Does a Live Photo have sound?

Usually. The movie part is a QuickTime movie, and Apple says the camera records what happens before and after the shot, including the audio. A Live Photo made from a silent video or a still photo has no sound.

Where is the identifier that pairs the two files?

In the movie it is the QuickTime content identifier, which Apple documents. In the still it sits in Apple's maker-note metadata; Apple documents that dictionary but not the exact key.

I have the photo and the video as two files. Why won't they combine?

Photos only pairs a still and a movie that carry the same identifier and the expected metadata. Two files that were not made as a pair, or were re-encoded on the way, will not combine just because their names match.