To find video source material, you need the pages where the clip's frames actually appear. Upload the video and this tool checks the web for matching imagery, then lists every matching page together with the number of frames it matched — the raw evidence a real source investigation needs.
The results are matching pages and possible sources. That distinction matters: web matching finds where the footage appears, but it cannot prove which page uploaded it first. Anyone who promises a guaranteed original source from an image match is overpromising.
The find video source tool above needs an MP4 or WebM file up to 100 MB and 10 minutes. No account, no URL to paste, nothing installed — the rest of this page explains how to run the search and, more importantly, how to judge what comes back.