How to Convert a Video for TikTok

The fastest way to convert a video for TikTok is to re-export it as an MP4 with H.264 or HEVC inside. Both of which appear on TikTok's own list of supported formats and codecs. Here's what's actually going wrong when a file is refused.

Convert a video for TikTok to a format it publishes

TikTok's Content Posting API documentation lists what it accepts, and it's worth reading carefully because it names two separate things.

Formats: MP4 (recommended), WebM, MOV. Video codecs: H.264 (recommended), H.265, VP8, VP9.

Both lists have to be satisfied. A file with a .mp4 extension carrying an exotic codec is on the first list and off the second, and that combination is where most upload failures live.

Container versus codec: what actually breaks playback

The container is the box. MP4, MOV and WebM are all boxes, and they mostly hold the same kinds of things. The codec is how the picture inside was compressed, H.264, H.265 (also called HEVC), VP8, VP9.

Renaming a file changes the label on the box and nothing else. That's why the "just change the extension" advice fails: the video inside is still encoded the way it was, and any player that couldn't decode it before still can't.

Converting properly means decoding the whole video and encoding it again into a codec on the supported list. It costs a generation of quality, which is why it belongs at the end of the edit rather than the start.

And format is only one of several ways a file can fall outside spec. The same documentation sets a picture size between 360 and 4096 pixels, a frame rate between 23 and 60 FPS, and a maximum file size of 4GB. All of which a perfectly valid MP4 can violate.

An export that checks itself before calling itself done

Montaj exports one predictable file: 1080x1920, HEVC, in an .mp4 container. What's less common is that the export verifies itself. It checks the duration, the dimensions and the audio, and decodes frames back out of the finished file before declaring it complete. That's the failure mode this whole page is about: a file that looks fine in the export dialogue and won't play elsewhere. Everything runs on your device, with nothing uploaded. Converting a video for TikTok stops being a recurring chore when the export was correct the first time.