How it works, and where it stops

What it does

Every recipient gets a copy that looks the same as everyone else's but carries a faint pattern, derived from a secret key and the recipient's label, spread across the picture where there is enough texture to hide it. To trace a leak, the pattern is looked for in the leaked file and compared with each recipient's. Nobody is named unless the match is far stronger than chance.

Videos are made as two versions cut into short segments, and each recipient's copy takes each segment from one version or the other according to their own pattern. That is why a video costs the same to mark however many people receive it. Tracing reads which version each segment came from.

What it survives

Measured on textured footage: recompression, resizing down to about a third of the size, cropping, mirroring, brightness and colour changes, blur, grain, and a screen recording of the video playing. Photos survive JPEG at low quality, crops and resizing.

What it does not survive

• Flat or dark pictures. Cartoon shading, slides, black backgrounds and clear sky carry little. The tool tells you when this happens; those copies are traceable when shared as they are or lightly recompressed, not after heavy recompression.
• Small pictures and heavy crops. Mark the full-size original, not a thumbnail.
• A phone filming a screen, AI upscaling or "enhance" passes, and frame interpolation.
• Someone who knows it is there. Strong noise plus blur, or averaging several recipients' copies together, damages it. Treat it as deterrence plus evidence, not a lock.
• Short leaks of videos. Naming one person among several needs about two minutes of leaked video. Less than that gives a lead, not a name, and the result says so.

What a result means

A match is evidence, not proof. Someone else may have passed the copy on, or the account that shared it may have been compromised. Check against how and when you sent each copy before acting.

This free service

Files up to 300 MB, videos up to about 5.4 minutes of 1080p, up to 100 recipients, one job at a time per person. Heavy jobs wait in a queue. Your case file, not this site, holds the key.