THM file
Also known as: thumbnail file, .THM, GoPro THM
A tiny JPEG thumbnail an action camera saves next to each video clip, so the camera screen and phone app can show a preview grid without opening the video.
Updated
What it means
A THM file is a thumbnail: one small still image that represents a video clip. GoPro writes a THM next to every recording, and the idea goes back to older digital cameras from Canon and others that used the same trick. Despite the unusual extension, the content is an ordinary JPEG, just a few kilobytes in size.
Its job is to make browsing fast. When you open the gallery on the camera's rear screen or in the phone app, showing dozens of THM images is instant, while decoding the first frame of every HEVC clip would make the grid crawl. The thumbnail carries no video, no audio and no metadata you need for editing.
How it works in practice
On a GoPro card you will find the THM in the same DCIM folder as its clip, with an identical base name: GX010045.MP4 sits next to GX010045.THM, alongside the LRV preview. Every chapter of a long take gets its own set, so a single ride split into chaptered files leaves several THM files behind.
Rename one to .jpg and any image viewer will open it, which is occasionally handy for checking what is on an unlabeled card without loading the video. Desktop editors and media managers ignore THM files and build their own thumbnails, so most people simply exclude the extension when copying. A filter such as *.MP4 in the file manager, or an offload tool set to video only, keeps them off your drive.
What to watch out for
THM files are harmless, but they cause small headaches. Dragging a whole DCIM folder into an editor or cloud backup can trigger errors about unsupported files, or clutter a project with dozens of icons that look like media. Filtering by extension avoids that.
Be careful with cleanup while the card is still in use. Deleting THM files directly on the card can leave blank tiles in the camera gallery or in GoPro Quik. And never judge a clip by its thumbnail alone: the THM shows only one frame from the very start, which tells you nothing about whether the dead time ends ten seconds or ten minutes in.
How RawClip handles it
RawClip does not read THM files, and they add nothing to your video, so there is no reason to upload them. Pick only the video clips from the card. The AI looks through the footage itself to find jumps, faces and peak action, rather than relying on a single preview frame, and assembles them into one highlight.