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Klargrid

Tools for your workbooks that never see your data

Klargrid repairs, cleans, combines and compares Excel and CSV files in your browser. Here is what sets it apart, and how to check it.

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The problem

A company's Excel file rarely holds harmless data: salaries, margins, customer details, bank statements. To merge two exports, fix a CSV or compare two versions, online tools ask you to upload those files to their servers. Excel add-ins install with administrator rights and only run on Windows.

For many professions (payroll, accounting, healthcare, the public sector), this is not a preference: uploading to a third party is simply forbidden.

What we do instead

All the work happens inside your browser tab. The file is read from your disk, transformed in memory, and the result goes back to your disk. No server receives it: this site is a set of static files, and the page working on your workbook is not allowed to open a connection to any other domain.

  • Nothing is sent

    No upload, no queue, no account. The page's security policy forbids it, and the browser enforces it.

  • Nothing gets lost

    A repaired workbook keeps everything that was not fixed, byte for byte: charts, macros, validations, pivot tables.

  • We show before we act

    Every transformation is previewed: what will be removed, merged, converted. You save knowing what you get.

Nothing gets lost, and it is checked

Repairing a workbook with a generic library means reading it and writing it back whole, losing whatever the library does not understand: charts, formatting, validations, macros. Klargrid rewrites only the part of the file it fixes, and copies the other parts as they are, compressed bytes included.

Then it reads the output back and compares it with the original: every value, every formula, at the same address. The result appears next to the file, for example "184,312 cells read back, no difference beyond the requested fixes". If the comparison fails, the file is not offered.

How to check it

  1. Open the developer tools

    Press F12, Network tab. Drop a file and run a tool: no request leaves with your data.

  2. Turn off the network

    Once the page has loaded, switch to airplane mode and keep working: everything still works.

  3. Read the security policy

    In the page source, the Content-Security-Policy tag carries connect-src 'self': the browser refuses any connection to another domain. The details.