Resync Clip

Make any video play properly on iPhone and iPad.

Drop your videos here or click to browse · MP4, MOV, M4V Up to 50 MB per file

Why videos don't play on iPhone

A video can be perfectly valid and still refuse to play on iOS. There are four common reasons, and Resync Clip detects and repairs all of them.

The moov atom is at the end of the file

An MP4 keeps its metadata — track layout, codecs, sample offsets — in a box called moov. When it is written after the media data, a player has to download the entire file before it can start. Moving it to the front is called faststart, and it is what makes a video begin playing immediately.

HEVC tagged hev1 instead of hvc1

hev1 and hvc1 describe the same HEVC video; only the container tag differs. Apple platforms play hvc1 inline and refuse hev1. Because the encoded video is identical, the repair is a tag rewrite — not a re-encode — so quality is untouched.

An unsupported codec or profile

MPEG-4 Part 2, ProRes and VP9 need converting to H.264. So do the H.264 High 4:2:2 and 4:4:4 profiles, which are valid H.264 that iOS will not decode.

Audio that plays as silence

AC-3, E-AC-3 and PCM audio tracks leave you with a video that plays with no sound on iOS. They are converted to AAC.

Your videos stay on your device

Checking a video reads only its atom headers and moov box — a few kilobytes, whatever the file size. Faststart and HEVC-tag repairs are container rewrites, so they run entirely in your browser and the video is never uploaded. Only a file that genuinely needs re-encoding is sent to the server, and it is deleted once the result is returned.

Questions

Does it re-compress my video?

Only when it has no choice. Faststart and HEVC-tag repairs copy the encoded video across untouched, so quality is bit-for-bit identical to the original. A real re-encode happens only for a codec, profile or audio track that iOS genuinely cannot play.

Is there a file size limit?

50 MB for videos that need server-side conversion. Repairs that run in your browser have no practical limit, because nothing is uploaded.

Which formats can I use?

MP4, MOV and M4V. You get back an MP4 that plays inline on iPhone, iPad and Safari on macOS.

Does it work on Android or desktop?

The tool runs in any modern browser. The fixes target Apple's playback requirements, and the resulting files play just as well everywhere else — faststart in particular helps every platform start playback sooner.

Is it free?

Yes, and there is no account or sign-up.

What is left alone

10-bit HEVC from iPhone HDR recording plays fine on iOS and is not touched. Rotation metadata is honoured correctly by iOS. Timecode, subtitle and metadata tracks are ignored rather than flagged, because iOS simply skips what it does not understand.