Features
Keys stay with you: client-side pseudonymisation explained
With Keys stay with you, personal data is detected and replaced in your own browser, and the key that reverses the tokens stays in the browser's storage or in a key file you download. Neither the document text nor the key is sent to or stored by LEXARIS. It suits text documents; scans, audio and video need Cloud.
Key points
- Detection and replacement run in your browser, not on LEXARIS servers.
- The key lives in the browser's IndexedDB or in a key file you download, never in a cookie.
- Text and documents with a text layer only: no OCR, audio or video.
- Lose the key file and clear the browser, and the data cannot be restored.
What client-side pseudonymisation means
Client-side pseudonymisation means the work happens on your device. Your browser finds the personal data, replaces it with tokens and keeps the key; neither the source text nor the key is sent to LEXARIS.
Pseudonymisation is the replacement of identifying details with stand-ins, such as [PERSON_1], while keeping a separate key that can reverse the change. "Client-side" means the replacement and the key live with you, the client, rather than on a service provider's servers.
In LEXARIS this way of working is called Keys stay with you. The alternative, Cloud, processes documents on our servers in St Petersburg, Russia (EU, UK, US and Swiss regions are planned and not yet available). Both use the same idea of reversible tokens; they differ in where the processing and the key live.
How Keys stay with you works, step by step
The workflow is the same as usual, anonymise, check, send, restore, but the sensitive steps happen in your browser.
- Anonymise locally. You open a document or paste text. Detection and replacement run in the browser, so the original values never leave your device.
- Check. The GO/NO-GO check runs before sending. When you send through LEXARIS, an unchecked document cannot be sent. The check reduces risk; review the result before sharing.
- Send. Only the tokenised text goes to the AI you choose, such as ChatGPT, Claude or Gemini.
- Restore. When the answer comes back, your browser uses the key to put the real values back.
Tenant John Smith, phone +44 20 7946 0958, is two months in arrears.
Tenant [PERSON_1], phone [PHONE_1], is two months in arrears.
The full workflow is described in how to use AI with client documents.
Where the key lives, and why not in a cookie
The key is kept in the browser's IndexedDB, or in a key file that you download and store yourself. It is never placed in a cookie.
IndexedDB is a storage area built into modern browsers. Data saved there stays on your device and is not sent anywhere unless a page's code sends it. A key file is simply the key saved as a file, which you can keep on your computer, a company drive or a password manager that stores files.
Cookies work differently. Browsers attach cookies to every request they make to the website that set them. A key stored in a cookie would therefore be sent to the server again and again, and it would not really stay with you. That is why cookies are not used for keys.
What you gain: fewer processor and transfer questions
Because LEXARIS never receives the document content or the keys in this mode, it does not process that personal data on your behalf. That removes one party from the chain you need to assess. Your account details and ordinary access logs are processed as described in the privacy notice.
With Cloud, LEXARIS acts as a processor under a data processing agreement, which is a normal and well-understood arrangement under Article 28 of the GDPR. With Keys stay with you, there is no personal data reaching LEXARIS to process, so questions about LEXARIS as a processor or about transfers to its servers largely fall away.
You still need to think about the AI provider that receives the tokenised text, and about the context around the tokens. The guide on pseudonymisation versus anonymisation under the GDPR explains how recent case law approaches that question.
Limits: Cloud compared with Keys stay with you
Keys stay with you trades some features for control. Anything that needs heavy server-side processing, such as OCR or video tracking, is only available in Cloud.
| Cloud | Keys stay with you | |
|---|---|---|
| Where detection runs | Our servers in St Petersburg, Russia (EU, UK, US and Swiss regions planned) | Your browser |
| Where the key is kept | Encrypted, on our servers in Russia | Browser IndexedDB or a key file |
| Document content sent to LEXARIS | Yes, processed under a DPA | No |
| Formats | All 13, including scans, audio and video | Text and documents with a text layer |
| OCR, audio, video | Yes | No |
| History, team workspaces, audit log | Yes | No |
| Restore from | Any device | Same browser, or anywhere with the key file |
| If the key is lost | Keys are held encrypted in the Cloud | Data cannot be restored |
The Cloud and Keys stay with you comparison on the main page sets out the same choice, and the supported formats section lists what each format needs.
Who should choose which
Choose Keys stay with you when keeping personal data entirely off third-party servers matters more than convenience. Choose Cloud when you need scans, media, team features or restoring from anywhere.
- Keys stay with you suits individual practitioners and small teams working mainly with Word documents, text-based PDFs and emails, and organisations whose policies discourage sending client data to additional vendors.
- Cloud suits teams that handle scanned documents, recordings or video, need shared workspaces and an audit log, or want to restore answers on any device. Cloud processing of PHI is not currently offered.
Many teams use both: Keys stay with you for everyday text, Cloud for the files that need it.
What happens if you lose the key
If the browser storage is cleared and the key file is lost, the tokens cannot be turned back into the original values. LEXARIS does not have a copy, so it cannot help recover them.
That is the other side of the guarantee. To avoid surprises, download the key file for anything you may need to restore later, keep it with the project it belongs to, and remember that clearing site data or using a private window can remove what the browser has stored.
The tokenised text itself stays readable, so a lost key does not lose the AI's work; it only means the real names and details have to be filled in by hand. For a closer look at how tokens compare with other modes, see seven ways to replace personal data.
Frequently asked questions
What is client-side pseudonymisation?
It means personal data is found and replaced with tokens on your own device, in the browser, before anything is sent anywhere. The key that links tokens back to real values is also kept on your side.
Why is the key not stored in a cookie?
Browsers send cookies to the server with every request. A key kept in a cookie would travel to the server each time, so it would not really stay with you. IndexedDB and a downloaded key file do not have that behaviour.
What happens if I lose the key?
If you have cleared the browser storage and do not have the key file, the tokens cannot be turned back into the original values. Nobody, including LEXARIS, holds a copy. Keep the key file somewhere safe.
Can I process scanned PDFs with Keys stay with you?
No. This mode works with text and documents that already have a text layer. Scans need OCR, and audio and video need transcription and tracking, which are available in Cloud.
Sources
This guide is general information, not legal advice. Check the current text of the law and regulator guidance for your situation.
Try it on your own document
The demo runs entirely in your browser. Nothing is sent anywhere.