How KolTheia works

The short version

KolTheia answers one question: was this photo or video really captured by a camera, at this moment? It proves it. It never guesses from the pixels, and it never says something is fake — it can only say a proof exists and checks out, or that it doesn’t.

It also answers a second, separate one for any file at all: who registered these exact bytes first? See Registering a file. The two answers are never mixed: a registration says who had a file first, not that it is real.

How to use it

Create your account. Give your email and choose a password. KolTheia emails you a 6-digit code to confirm the email is yours, then you pick a username: the name shown on your captures. Your email stays private. From then on you log in with your username or email and your password.
Capture. Use the camera inside KolTheia. It works like your phone’s own camera: photo and video, the lenses and zoom your phone offers, tap to focus, flash, a timer, a level line that turns yellow when your phone is level (switch it on in the settings; it is never part of the picture), and a note when it is too dark for a good picture. For video you choose the frame rate and the size, up to 4K, and the sealed copy keeps that same size; 4K takes noticeably longer to seal and send than HD. Videos are recorded with sound. Your browser asks for the microphone the first time; if you say no, the video is silent and KolTheia tells you so. There is deliberately no “choose a file” button — that would let anyone seal a photo they didn’t take.
Save the sealed file and copy its code. KolTheia shows both the moment sealing finishes, because it keeps no permanent copy of your photo or video. Until you have saved it, KolTheia holds one more copy in memory only, for 15 minutes at most, so a dropped connection or a switched-off phone does not lose it: it is on My Captures under “Waiting for you to download”, and you can delete it there at once. The code is also kept in My Captures, so you can copy it again later, next to a small picture drawn from the file’s fingerprint so you can recognise a capture at a glance (a picture for recognising, not a proof). On the phone that took it, that picture also carries a soft drawing of the shot behind it, made on the phone and kept only there.
Anyone can check it on the Verify page — no account, nothing to install. They can drop the file, or just paste the code to see the record.

Install it on your phone or computer

KolTheia is a web app: there is nothing to download from an app store. Install it and it gets its own icon and opens full screen like any other app. On a phone this is worth doing: it keeps the camera screen uncluttered, and it keeps the signing key KolTheia holds in your browser safe from the browser’s clean-up of websites you have not visited for a while.

You do not need to install KolTheia to check a file: the Verify page works in any browser, with no account.

What the results mean

Eight possible answers. The first six are about files KolTheia sealed; the last two are about files it didn’t.

Verified capture: This exact file was captured and sealed by a real device. Nothing has changed since.
Tracked edit: Edited after capture, and the edit history says which tool did it.
Recompressed: For a video. Not the original file, but its picture matches a real capture everywhere KolTheia looked: it was recompressed, for example by a messaging app. The answer lists what else it found — resized, cropped, shortened (and which seconds are left), mirrored, turned — and that nothing added or changed was found in the places checked. That is a finding, not a guarantee.
Altered, traced: Not the original file, but it traces back to a real capture. The answer says what was found: a filter over the whole picture is shown in green (nothing wrong with it), and something introduced in one place is shown in yellow, with roughly where (and, for a video, when). A copy KolTheia can only trace by the hidden mark or by how it looks gets no list of what was done.
Altered: You gave a capture ID, but this file doesn’t match it. It changed after it was sealed.
Signature invalid: A record exists for this file, but its proof no longer checks out. Don’t trust it.
Content credentials: KolTheia didn’t seal this file, but it carries Content Credentials from the camera or app that made it — for example a Google Pixel, Samsung Galaxy, Sony, Leica, Nikon or Truepic. KolTheia checks the signature and whether the signer is on the official trust list, and reports who signed it, the device, and whether the credentials say it was edited or made by AI. It’s the maker’s own statement: KolTheia can’t add anything about when or where it was taken.
Unverified: KolTheia has no record of this file and it carries no credentials. That doesn’t make it fake — only that nothing vouches for it.

Registering a file

Not everything you make comes out of the camera: a script, a song, a design, a document, a photo you already took. On the Register page, choose the file. Your browser works out its fingerprint (SHA-256) and sends only that, with the file’s name, its size and a description if you add one. The file itself never leaves your device. If nobody has registered those exact bytes before, KolTheia records that your account registered them, at that moment, and gives you a code starting KR- with a certificate anyone can open.

First one wins. The same bytes can be registered once. Anyone who later tries gets the first registration’s certificate instead. A file that is already a KolTheia capture cannot be registered: its capture certificate already proves when it existed.

What it proves. That these exact bytes existed by then and that your account registered them before anyone else did with KolTheia. Each registration is sealed, added to the same public log as every capture, and its fingerprint is time-stamped by the same outside authority, so it does not rest on KolTheia’s word alone.

What it does not prove. That the file is real, unedited, or what it shows; that you made it; or that you own any right in it. Anyone can register a file they have, so a registration is evidence of who had it first, not of who made it. It is not a copyright registration or any other legal title. And it covers the exact bytes only: re-save, convert, compress or crop the file and it is a different file.

Checking. Open the certificate from its code (the Verify page sends a KR- code there), and choose your copy of the file on it: your browser compares the fingerprints. Dropping a file on the Verify page also says, in its own box, whether those exact bytes were registered. Your registered files are listed under My Captures.

Proof beyond KolTheia’s word

A record on its own is only KolTheia’s word that it is the same as when it was accepted. Three things make it stand on more than that. Each one is on the capture’s certificate page.

The seal on the record. KolTheia seals its own record of every capture and chains one device’s records together, so an edited or removed record is caught by an audit KolTheia runs every day. Only KolTheia can check this seal.

An independent time-stamp. Right after a capture is sealed, KolTheia sends a public time-stamp authority the fingerprint of the sealed file (the fingerprint only, never the file) and keeps its signed answer. That is proof the file existed no later than that moment, by a clock that is neither yours nor KolTheia’s. You can download the answer from the certificate and check it with OpenSSL, without KolTheia.

A public log. Every record is also added to an append-only public log that KolTheia signs and the same authority time-stamps. On a certificate, “Check the proof in this browser” makes your own browser recompute the proof, trusting nothing the page says. If KolTheia later changed, back-dated or removed a record, anyone who had kept an earlier copy of the log’s head could prove it. That protection only reaches people who kept one, which is why the heads are public and time-stamped.

None of these show the scene was real. They show a file and its record are unchanged, and existed by a certain time.

What KolTheia keeps

Not your photos. KolTheia seals your capture and hands it straight back to you. It keeps only a small record of the seal — a fingerprint of the file, when it was captured, your username, which device, what the phone and browser said they were (for example “Pixel 9, Chrome, Android 15”), the label you chose, and the general area (about 5 km across) if you allowed location. For a video it also keeps a small note about the pictures: a coarse description (a few dozen distinctive points every half second and four small squares of colour and brightness every fifth of a second, about 180 KB for each minute) that lets KolTheia recognise a copy and say what was done to it. It is not a copy and cannot play the video; the best rebuilding we tried from the squares gave only a blurry colour mosaic of about half the picture, with no faces and no writing. So there is no stored copy of your media to leak, sell, or hand over. The one exception is a sealed file you have not yet picked up: it is kept in memory only (never written to disk) for 15 minutes at most, then deleted.

Two other places hold fingerprints, never the media: the public log, which holds a fingerprint of each record (and, for as long as the record exists, the same label and device name the record has), and the time-stamp authority, which sees only the sealed file’s fingerprint. If a record is erased, the log keeps just its fingerprint. The soft drawing of each shot stays on the device that took it: KolTheia never receives it. The note about a video’s pictures is not in the public log and is erased with the record.

Your account

Your email is private: it is only used to confirm your account, to reset your password, and for security messages. Your username is separate: it is the public name on your captures, and you can change it from your account page.

You sign in with your username or email and your password (at least 10 characters; a few ordinary words strung together works well). KolTheia refuses a password that is very common or that appears in a known data breach, and it stores only a scrambled hash of it. Keep me signed in keeps a device signed in for 180 days. Emailed 6-digit codes are used only to confirm a new email and to reset a forgotten password: choose Forgot password on the log-in page. After several wrong passwords an account pauses for 15 minutes.

You can add a passkey too, right after you sign in or from your account page at any time: that lets you log in with the Face ID, fingerprint or screen lock you already use to unlock your phone or computer, instead of typing a password. Your face or fingerprint never leaves your device, and KolTheia never sees it. A passkey is always optional.

To see or remove what KolTheia holds about you, see your data.

What it can’t promise

Where your signing key lives. Each capture is signed with a secret key that stays on your device and is never sent to KolTheia. Right now that key is kept by your browser — real protection, but still software, so someone who fully took over your device could in principle copy it. Phones and laptops also have a security chip (the same one behind Face ID) where a key can be used but never copied out. That is the stronger option, and KolTheia is built to use it, but it isn’t switched on for capture yet.

Device details. The phone model, browser and camera settings shown on a certificate are what the device reported at capture. KolTheia locks them into the signature so they can’t be edited later, but it can’t independently prove the device told the truth.

When. The capture time is your device’s own clock, held to what is possible (never in the future); the time KolTheia received the capture is shown beside it. The independent time-stamp shows the sealed file existed by a moment, not when it was captured.

Sound. A video’s sound is whatever the microphone heard. KolTheia keeps it in the sealed file but cannot prove it is real, any more than it can prove the picture is.

Location. It is what your device reports. KolTheia is sent only the general area (a square about 5 km across) and a sealed fingerprint of your exact spot; the exact spot stays on your device, and you can show it later, which anyone can check against the seal. KolTheia can’t independently prove your device wasn’t told a false location, and if you clear this browser’s data without saving the reveal file from the certificate, nobody can recover the exact spot.

Fake cameras. Someone can feed a fake video feed into a browser. On the front camera, KolTheia flashes a random colour pattern and checks it shows up in the picture, which a pre-recorded feed can’t know in advance. A further check by the phone itself needs the native app, which doesn’t exist yet, so KolTheia says “unavailable” rather than pretend.

Copies that were changed. KolTheia can hide a tiny mark in a capture, but it is switched off at the moment for photos and videos: at the strength it needs to survive real sharing it left a faint ripple you could see, and a seal should not change how your picture looks. So a sealed file carries no hidden mark today, and a changed copy is traced by the note described below instead.

When there is no mark. KolTheia also compares what the picture looks like against a tiny fingerprint it keeps for each capture (64 bits). That can still catch a heavily squeezed photo, or a copy of a video’s first 16 seconds, but not a cropped, turned or mirrored one, and it is reported as a weaker “looks like a capture” match, never as proof, because a photo of a screen would look the same. The exact-file seal, and the Content Credentials built into the file, never survive a change, by design: they prove this precise file.

Content Credentials. Every sealed file carries them, in the open C2PA standard, so other checkers can read it without KolTheia. They are signed by KolTheia’s server and carry your device’s own signature inside, plus an outside time-stamp when the time-stamp authority answers while sealing. KolTheia’s signing certificate is not yet on the official C2PA trust list, so other checkers show them as intact but from a signer they don’t recognise.

What was done to a copy. For every photo and video KolTheia keeps a small note (distinctive points and small squares of brightness and colour) and can compare a copy with it, then say what it found: recompressed, resized, cropped, shortened (a video), mirrored, turned, a filter over the whole picture, or something introduced in one place. It says what it found in the places it checked, not that nothing else changed: a small or brief change can fall between the squares, and in our tests a few such changes were missed. A copy squeezed to well under 360 pixels wide can be wrongly flagged as changed, and a cropped copy of a steady pan can too; a very plain scene gives it little to hold on to. For a photo, a copy that was photographed at a slant, turned, bent or drawn over is usually still lined up when about half of it or less is covered (for photos sealed from 29 October 2026; older ones keep fewer points, so they line up less often); with three quarters or more covered it usually is not, and is reported as not verified. When a photo lines up only loosely, the answer says so, because a bent copy and a different photo of the same scene can look alike.

Edit histories. Very few photos on the internet carry them today, and most apps strip them when you upload. KolTheia reads them when they’re there, but its own seal is the foundation.