Local-first data masking
Give AI your data.
Keep your data.
ShiftMask builds a safe local copy of your Excel, CSV and SQL — table relations intact, every date shifted by one offset, every name masked. The real records never leave your machine.
Windows · works with Wi-Fi off
| customer_id | name | invoice_date | amount |
|---|---|---|---|
| C-10482 | Nowak Logistics | 2026-08-14 | 18,420.00 |
| C-10483 | Baltic Foods | 2026-08-15 | 4,990.50 |
| C-10482 | Nowak Logistics | 2026-08-28 | 7,110.00 |
| customer_id | name | invoice_date | amount |
|---|---|---|---|
| C-10482 | Nowak Logistics | 2025-10-29 | 18,420.00 |
| C-10483 | Baltic Foods | 2025-10-30 | 4,990.50 |
| C-10482 | Nowak Logistics | 2025-11-12 | 7,110.00 |
0
Bytes sent to any server
Nothing to leak, because nothing leaves.
No account, no upload, no telemetry. ShiftMask reads your files, builds the masked copy in a local DuckDB database, and writes it back to your disk. Pull the network cable and it still works.
What survives
Masked data is worthless if the analysis breaks.
Most tools scramble values row by row. That destroys exactly the properties a model needs in order to write code that runs against your real database later.
Referential integrity
Keys are masked identically in every table, so joins, lookups and relationships still resolve.
Time intelligence
One shared offset moves the whole calendar. Intervals and period boundaries hold, so YTD, YoY and rolling averages return the same shape.
Cardinality and shape
Row counts, distinct counts and value distribution stay realistic, so the code is sized for your data, not a toy sample.
Personal data
Names, emails, phone numbers, addresses and free-text identifiers are replaced by generated values. Nothing traces back to a real person.
The method
Three moves. None in the cloud.
Point it at your files
Excel workbooks, CSV files or a SQL database. ShiftMask reads the schema and detects primary and foreign keys to map how your tables actually connect. You confirm or correct the map.
Move the calendar, mask the rest
Every date moves by one project-wide offset. Names, emails and identifiers become generated stand-ins — the same input always yields the same output, so one customer stays one customer across every file.
Hand the copy to a model
Send the safe package to ChatGPT, Claude, Gemini or a coding agent. You get back a dashboard, report or app. Point that code at your real database offline and it runs unchanged.
Built for
Two people, one bad afternoon.
The analyst
You already use AI to write DAX, SQL and Python. You also know that pasting a client extract into a chat window is the kind of thing that ends a contract. ShiftMask gives you something you can paste.
The owner
You want a report or a small internal tool without hiring anyone for three months. You are also the person who signs the data processing agreement. ShiftMask keeps the real records where they belong.
Pricing
Buy it once. It’s yours.
Core License
- Unlimited files, tables and projects — no time limit
- Excel and CSV sources
- Automatic relationship detection with manual override
- Date shifting and deterministic masking
- Export to anonymized Excel files
- Runs entirely on your machine, offline
SQL sources and DuckDB export are coming in a Pro upgrade — Core owners get a preferred upgrade price when it ships.
Get Core License$39
One payment, per device
Free updates for 1 year
Founding price — first 150 licenses
Before you trust it
The questions that actually matter.
Is it safe to put company data into ChatGPT?
Not the real data. Anything you paste leaves your control, and most public AI tools give you no contractual guarantee about where it goes. ShiftMask exists so you never have to — you send a structurally identical copy in which no value maps back to a real person or account, and you get working code back all the same.
Does my data leave my computer?
No. ShiftMask is a desktop application. It reads your files locally, builds the anonymized copy in a local DuckDB database, and writes the output to your disk. You decide what, if anything, gets sent anywhere.
Does masking break my Power BI time intelligence?
That is the specific failure ShiftMask was built to avoid. Random date replacement destroys intervals, which breaks YTD, YoY and every rolling calculation. ShiftMask moves every date by one shared offset instead, so the distance between any two events is unchanged and time-based measures return the same shape.
How do I anonymize an Excel file for AI?
Open the workbook in ShiftMask, confirm which columns hold personal data — it proposes a classification automatically — and export. You get a new workbook or a DuckDB file with the same sheets, columns and relationships, and with names, identifiers and dates replaced.
Does this make me GDPR compliant?
No tool can make that promise for you, and be careful with any that does. What ShiftMask does is remove personal data from the copy you share, which is usually the hard part of using public AI tools lawfully. Your obligations under GDPR, and under HIPAA if you work with health data, still depend on your own processes.
How is this different from an enterprise masking platform?
Those are built for test environments, priced for enterprise budgets, and usually run as a service. ShiftMask is a desktop app for one person with one project and a deadline, sold for one payment, and it never sends your data to a server.