Video metadata before upload: an MP4 and MOV privacy checklist.

Why video metadata is different

Video files are containers. An MP4, MOV, or M4V file can hold media tracks, timing data, subtitles, thumbnails, chapters, and metadata atoms. Some atoms are required for playback, while others can include text fields such as creation date, software name, comments, author labels, or encoder information. Cleaning video requires more caution than removing a simple text field.

Verify playback after cleaning

A cleaned video is only useful if it still plays. Open the output before upload. Check the first seconds, the middle, and the ending. Listen for audio, confirm captions or overlays are still present, and test the file on the platform or device where it will be used. This is especially important for client delivery.

Client delivery considerations

For client delivery, avoid sending a cleaned file without confirming that the client expects a public-ready copy. Some clients need original metadata for records or editing. Others only need the finished clip. Clear naming and a short delivery note can prevent confusion between source files and cleaned public exports.

DataClean's MP4 and MOV boundary

The current cleaner overwrites recognized metadata text payloads in place. It preserves box sizes and byte positions so media offsets are not shifted. It does not transcode the video or audio. Consequently, a cleaned video can have exactly the same file size as its source.

This is selective cleaning. Track-header dates, some vendor-specific fields, timed metadata tracks and information inside encoded media can remain. The interface's success status does not certify removal of every location signal. Use a dedicated offline workflow if those fields are part of your threat model.

Inspect tracks as well as the container

ffprobe -v error -show_format -show_streams -of json original.mp4
ffprobe -v error -show_format -show_streams -of json original-clean.mp4

These read-only commands require FFmpeg's ffprobe. Compare stream count, codecs, duration, dimensions and the tags in both format and stream sections. Unexpected changes are a reason to stop. Then play the beginning, middle and end with sound. Inspection lists structure and tags; playback checks a different failure mode.

See the official ffprobe documentation for output options. The commands inspect files; they do not clean them.

Understand the video report

The current independent inspector compares top-level mdat media-data boxes byte for byte. The report deliberately has no video-metadata inventory: it does not parse every nested metadata atom. An empty block-count table for MP4 is therefore not a claim that the clip contains no metadata.

Unchanged mdat data is valuable evidence that the cleaner did not alter those encoded audio/video bytes. Timing tables, track configuration and player interpretation are outside that comparison. You must still test playback. A video that plays in one editor can have a codec unsupported by a recipient's browser.

A concrete playback test

1. Compare source and output duration and resolution with ffprobe.
2. Seek near the middle, where a damaged index can become noticeable.
3. Play the last seconds; check that audio remains synchronized.
4. Check rotation, captions and alternate audio tracks if your delivery depends on them.
5. Upload the cleaned copy to the intended destination and inspect its preview.

Same size, different metadata payload

DataClean preserves box lengths and replaces recognized text within those lengths. A source and output of the same size can therefore contain different descriptive text. File size alone cannot confirm success or failure. If ffprobe still shows a field you need removed, stop and choose a tool that explicitly supports that field. Do not repeatedly clean the same output expecting unsupported fields to disappear.