A shared spreadsheet in Google Sheets™ breaks quietly. Nobody means to — someone types a number over a total, pastes a column from an email (which skips the dropdown), sorts one column on its own, renames a header, or leaves a filter on so everyone else sees half the rows.

Shared Sheet Guardrails sets up guardrails from what's already in your sheet in a couple of minutes, then checks what's been broken since.

SIX WAYS A SHARED SHEET BREAKS — AND WHAT IT CHECKS
- A total typed over: a formula replaced by a number, including the first and last rows Google Sheets™' own checks skip.
- A paste past the dropdown: values that break a column's dropdown, date or number rule, and near-duplicates like "done", "Done " and "Completed".
- One column sorted alone: names no longer on the same row as their data.
- A filter left on for everyone.
- A range that stops at row 50 while the data runs on.
- A blocked ARRAYFORMULA: one typed cell and the whole column shows #REF!.
Plus: broken references, errors spreading, lost dropdowns on inserted rows, duplicate IDs, numbers stored as text, renamed headers, deleted tabs, and an audit of every protection on the tab.

THE GUARDRAILS ARE GOOGLE SHEETS™' OWN
Protected ranges (warning or locked), dropdowns and data validation, red highlights, a frozen header and a note on each header. So they work for every collaborator, on every device — including phones — and nobody else installs anything. Remove them all in one click, free, at any time.

WHAT PRO ADDS
Checking is free and unlimited, and so are Quick protect (formulas and headers, warning only), Undo last setup and Remove guardrails. Pro (£4/month or £29/year, 50% off for schools and charities) adds the full setup wizard, one-click fixes, Check all tabs, contracts you can save, refresh, export and apply to similar tabs, and a report. 3 activations, 30-day full refund. Only the keeper pays; collaborators never need it.

WHAT PROTECTION CAN'T DO
The file's owner can always edit, anyone with edit access can make a copy, and viewers are unaffected. These are guardrails, not security.

YOUR DATA
The check runs in the sidebar, in your browser. Your spreadsheet's content never leaves Google — the only thing sent anywhere is a licence key and an anonymous install id, and only to activate or check a Pro licence. It asks for "this spreadsheet only", never your Google Drive™.

Google, Google Sheets™, Google Workspace™ and Google Drive™ are trademarks of Google LLC. Shared Sheet Guardrails is not affiliated with or endorsed by Google.