Introducing Velum: masking before the model, not after

Every time you paste a client record into ChatGPT or Claude, you make a trade. You get the answer, and you hand over data that was never yours to give away. Names, addresses, ID numbers, medical notes. Once it is sent, it is sent.

We built Velum because that trade is avoidable.

The problem is architectural

Most privacy tooling in this space is a wrapper. It puts access controls or a scrubbing API in front of a system that was still designed to move your data somewhere else. You end up trusting a second vendor to protect you from the first.

Velum does the work before anything is sent. It runs on your machine, finds the personal data in your text or your file, and replaces each value with a placeholder. The masked version is what reaches the model. When the reply comes back, Velum puts the real values in.

That is the whole idea, and it is deliberately unglamorous. The model still gets a coherent prompt, because the structure of the sentence is untouched. You still get a usable answer, because the placeholders come back out.

Reversible, not destructive

Redaction tools blank things out. That protects the data and ruins the answer: you get back a draft full of holes to fill in by hand, so people stop using the tool and paste the raw version instead.

Velum's placeholders are reversible. ⟦PERSON_1⟧ maps back to the real name, consistently, throughout the document. You can also choose pseudonymised masking, where the stand-in is fake but format-valid, which suits documents that have to keep looking like documents.

What "local" means here, precisely

The masking runs on your device and nothing you mask is sent anywhere. That claim is worth stating carefully, because vague versions of it are exactly what we are asking you to distrust in other tools:

• Detection and masking happen on your machine. There is no vendor server in the path, and no account to create.
• The desktop app does open a socket on 127.0.0.1, because the interface talks to the local engine that does the work. It is bound to your machine and cannot be reached from the network. "No network calls at runtime" means nothing leaves the device, not that no socket exists.
• The app writes a usage log to your own disk, with no personal data in it. Nothing uploads it. You can delete it.

We would rather be this specific and be checked than round it up to something cleaner.

What it does not do

It does not make you compliant. GDPR cares about what you do with personal data, and masking before disclosure to a third party is a genuine and useful control, but it is one control among many. We have no HIPAA or BAA posture today. SOC 2 is in progress and not finished. If a vendor tells you their tool makes compliance automatic, check what they mean.

It also does not catch everything. Detection is very good on structured identifiers and good on names and addresses, and it varies by language and document. Velum reduces exposure. It does not eliminate it.

Where to start

The macOS app and the browser extension both run for seven days with no account and no card. After that a licence key keeps masking on, and unmasking is never gated, so anything you have already masked stays readable either way.

Try it on your own documents: download Velum, or see where it fits.