iCloud photo from previous phone “format not supported”

Since you have not provided the Video file format in question, I am forced to guess the possibilities.

Why the iPhone 11 might have played them but the iPhone 16 cannot

Older iOS versions often included broader support for certain legacy video codecs and containers (for example, older QuickTime .mov variations or less common H.264 profiles). Over time, Apple has streamlined iOS to focus on modern, efficient codecs like HEVC (H.265) and standard H.264. As a result, a video that played fine on the iPhone 11 (with its older iOS) may now trigger an “Unsupported Format” error on the iPhone 16 because the newer iOS has dropped support for those outdated encoding methods.

Unsupported Formats on iPhone 11: MKV, AVI, WMV, FLV

Unsupported Formats on iPhone 16: MKV, AVI, WMV, FLV, MTS, VOB, MPG, F4V, AVCHD, MXF, TiVo

iPhone 11 supported MPEG Codecs, but iPhone 16 does not support them.

Both models can use third-party apps like VLC for iOS, Infuse, or KMPlayer to play unsupported formats like MKV or AVI. For editing or transferring, converting to MP4 (H.264) is the safest bet.

There are a few possible reasons why videos stored in iCloud, originally shot using an iPhone 11, might show as “Unsupported Format” when synced to an iPhone 16:

1. Videos were moved outside of iCloud at some point – For example, they may have been downloaded to a Windows PC and then uploaded again to iCloud. During this process, the file format, codec, or metadata may have been altered, either by the PC software or during the transfer.
2. Videos were not actually recorded on the iPhone 11 – They could have been captured on another device (such as an Android phone, DSLR camera, or GoPro) and later stored in iCloud alongside your iPhone 11 videos.
3. Videos were converted or modified – At some stage, someone may have re-encoded or converted the videos for another purpose (e.g., editing, compression, or sharing). This could have changed the encoding settings to a format that is no longer natively supported by the iPhone’s Photos app.

In such cases, re-exporting the videos from a compatible editor or converting them to H.264 or HEVC with AAC audio will restore full compatibility.

Messaging systems usually degrade any media to a more universal and lower resolution copy.

I always use Most Compatible when taking.