Watermark

Platforms add watermarks for two main reasons: brand recognition (so a TikTok shared on Twitter is visibly recognizable as a TikTok) and creator attribution (so the original creator's username travels with the video). The watermark is applied server-side at the moment a video is exported through the platform's official Save or Share button — it is not part of the original source MP4 stored on the platform's CDN.

This is why third-party downloaders can return watermark-free files: they fetch the underlying CDN MP4 directly, skipping the export pipeline that adds the overlay. The output is the same video at the same resolution, just without the visual logo. This is technically straightforward and entirely legal — the watermark itself is not copyrighted, and bypassing it does not bypass any DRM (none of these short-form platforms use DRM on user uploads).

Note that some watermarks are baked into the original upload — for example, a creator might embed their own logo into the video before uploading. Those cannot be removed because they're part of the source file itself, not an overlay added later.