Your spreadsheet stays on your computer
MindySheets is designed so your file never needs to leave your browser. Here is exactly what happens to your data, what goes to the AI and what we keep.
How your data flows
1. Your browser
Reads the file with a spreadsheet engine running on your computer. Profiling, cleaning, duplicate removal, formula checks and every calculation happen here.
2. MindySheets server
Checks your free credits, adds Mindy’s instructions and forwards the request. It keeps no file contents and no AI answers.
3. Claude
Plans calculations and writes explanations. It sees the summary and calculated results, not your file.
What is sent to the AI
Nothing is sent until you use an AI feature, such as Mindy’s first read, a question, a cleaning plan or a report. Then Mindy sends Claude a compact profile of the sheet you’re working on:
- file and sheet name, row and column counts;
- column names, detected types and how full each column is;
- summary statistics such as totals, averages, minimums, maximums and date ranges;
- the most common values in each column, and the problems MindySheets detected;
- a sample of about 12 rows, with long values shortened.
For a cleaning plan, the list of distinct values in short category columns (like Region or Status) is added so Mindy can spot spelling variants. For questions and reports, Claude asks for calculations and receives only their results — for example revenue by month — limited to 100 rows per calculation.
Switch on Private mode in the workspace toolbar and MindySheets holds back the sample rows and the values of personal columns (names, customers, emails, phone numbers, IDs and free-text notes). When a calculation result includes those values — say, your top customers — they’re replaced with placeholders such as [Customer #3] before reaching Claude, and swapped back to the real names on your screen.
About Claude and Anthropic
Mindy’s AI features use Claude, made by Anthropic, through Anthropic’s commercial API. Anthropic states that, by default, it does not use inputs or outputs from its commercial products to train its models, and that it automatically deletes API inputs and outputs within 30 days of receipt or generation, with limited exceptions. Read the details in Anthropic’s model training and data retention articles.
What MindySheets stores
| Data | Why | How long |
|---|---|---|
| Your spreadsheet | Not stored. It stays in your browser’s memory and is gone when you close the tab. | – |
| Daily usage counter | To give each visitor free AI credits fairly. Keyed to a one-way hash of your IP address. | 3 days |
| AI request log | Task type, model and token counts to monitor costs. No questions, data or answers. | Kept by the site owner |
| Email address | Only if you join early access, subscribe or contact us. | Until you ask us to delete it |
Other protections
- The Claude API key lives only on the server. Your browser never sees it and can’t choose Mindy’s instructions.
- All traffic is encrypted with HTTPS.
- Spreadsheet content is treated as data, never as instructions, so text hidden in a cell can’t redirect Mindy.
- MindySheets never changes your original file. You download a new copy with every change listed.
- No advertising trackers. If the site owner enables analytics, it records page views and feature usage, not your data.
Security questions
Where is my spreadsheet processed?
In your web browser, on your own computer. The file is read with a JavaScript spreadsheet engine; it is not uploaded to MindySheets.
What exactly is sent to the AI?
Column names and types, summary statistics (counts, totals, ranges), the most common values in each column, the problems MindySheets detected and a sample of about 12 rows. For cleaning plans, the list of distinct values in short category columns is included so Mindy can spot spelling variants. For questions and reports, Claude also receives the results of the calculations it asks for, such as “revenue by month”, capped at 100 rows each. With Private mode on, sample rows and the values of personal columns like names, emails and phone numbers are held back, and any such values in calculation results are replaced with placeholders like [Customer #3] that are swapped back only on your screen.
Does Anthropic train AI models on my data?
Anthropic states that by default it does not use inputs or outputs from its commercial products, including the Anthropic API, to train its models.
How long does Anthropic keep API data?
According to Anthropic’s privacy centre, it automatically deletes API inputs and outputs from its backend within 30 days of receipt or generation by default, with limited exceptions described in its policies.
What does MindySheets store?
Very little: a daily usage counter keyed to a one-way hash of your IP address (deleted after three days), an anonymous log of AI requests (task type and token counts, no content) and any email address you choose to give us.
Can I use MindySheets with confidential data?
Many people do, with Private mode switched on. If your organisation has a data policy, check that sending summaries to a third-party AI provider is allowed. Business and Enterprise plans will add stricter controls; contact us if you need them.
See it for yourself.
Open the workspace, switch on Private mode and try it with a sample file. Your own files never leave your browser.