What Detector Set v0.4 actually catches
Most spreadsheet bugs do not throw an error. They return a plausible-looking number that ends up in a board deck. SheetBrain's published Detector Set v0.4 ships six deterministic detectors that target common visible and silent bug classes. No AI is involved in the scan.
1. broken_reference — error
Cells displaying #REF!, plus VLOOKUP/HLOOKUP/INDEX calls whose column or row index exceeds the referenced range. The lookup-index case ships with an auto-fix that clamps the index.
2. mixed_text_number — warning
A column that looks numeric but has text-as-number cells ("15,000", "15K"). SUMIFS and AVERAGEIFS quietly skip them.
3. duplicate_lookup_key — warning
VLOOKUP and XLOOKUP return the first match. If your customer-ID column has accidental duplicates, some lookups have been wrong forever.
4. visible_formula_error — error
Formula cells returning #N/A, #VALUE!, #DIV/0!, #NAME?, #NUM!, #NULL!, or #ERROR!. Literal text values are ignored.
5. inconsistent_formula_pattern — warning
One-off formula deviations inside repeated same-column formula runs. It is deliberately conservative and skips dynamic reference formulas to avoid noisy pattern guesses.
6. missing_formula_pattern — warning
Hardcoded or blank cells inside repeated formula columns, only when the two formulas immediately above and two immediately below all share the same pattern. Review-only by design.
Each one is individually easy to review once you know it is there. The hard problem is that you do not. The full detector list, severity classes, scope limits, and content hash are pinned at /standard/detector-sets/v0.4/.
How to run a health check on your Google Sheet
Two ways, both free, both unlimited:
Option 1 — sidebar (one click)
- Install SheetBrain from the Google Workspace Marketplace (no credit card, free Gmail™ supported).
- Open any Sheet, then Extensions › SheetBrain › Open.
- Click the Check tab. The scan runs automatically on the active sheet.
- Review the findings list — each entry shows the affected cell, the issue type, the severity (error or warning), and fix or review guidance where available.
Option 2 — in any cell
If you prefer the formula bar over a sidebar, the same health check is exposed as a custom function. Pass the range as an unquoted reference (a quoted string is rejected with a usage hint):
Returns a 0–100 score like "87 — 2 issues" directly in the cell. The score starts at 100 and drops 15 per error and 5 per warning, with a floor at 0; "100 — All clear ✓" means no findings. Pair it with =SHEETBRAIN_ISSUES(A1:Z1000) in an empty area to spill a Cell / Issue / Severity / Description table. Tip: pass NOW() as a second argument, e.g. =SHEETBRAIN_HEALTH(A1:Z1000, NOW()), to bypass Apps Script's argument-value memoization and force a refresh.
Manual audit vs automated health check
You can do parts of this by hand. Ctrl+F with "search within formulas" enabled finds visible #REF! tokens. =COUNTA(range) - COUNT(range) tells you how many text-as-number cells are in a column. =COUNTIF(col, cell) > 1 in a helper column finds duplicate lookup keys. Manual works on small sheets, but on a 5,000-row workbook it takes 20-40 minutes; the deterministic scan takes about three seconds and runs the same checks consistently every time.
One bug class manual auditing cannot reliably catch is schema drift — when a column moves, your formula still has a value, just the wrong one. SheetBrain's Repair tab is designed for that case: it compares the active sheet against a captured schema snapshot and proposes safe rewrites. Repair is separate from Check and lives under the Pro plan.
What a clean report looks like
If your sheet is healthy, the verdict is Trusted: zero errors, zero warnings. Public audit reports SheetBrain generates after a Pro scan can be shared as proof — recipients see the verdict, the detector set used, and an expiry date, but no formulas, cell values, or column headers. The Spreadsheet Trust Standard documents what each verdict means and the privacy guarantees on the public report page.
The verdict thresholds in v0.4 are exact:
- Critical —
errorCount > 0(anybroken_referenceorvisible_formula_errorfinding). - Has open issues —
errorCount === 0 && warningCount > 0(anymixed_text_number,duplicate_lookup_key,inconsistent_formula_pattern, ormissing_formula_patternfinding, no errors). - Trusted — no findings of any severity.
Detector Set v0.4 has no info-class detectors yet; informational findings would not affect the verdict if added in a future detector set. Scope is bounded to 1,000 evaluated data rows and 50 columns per sheet.
Try a health check on your worst sheet
Free forever. Works on free Gmail™. Unlimited scans. No API key, no credit card.
Install on Google Workspace MarketplaceFrequently asked questions
What does a spreadsheet health check do?
SheetBrain's Detector Set v0.4 runs six deterministic detectors: broken_reference (cells displaying #REF! plus lookup formulas with column or row indexes outside the referenced range), visible_formula_error (formula cells returning common visible errors), mixed_text_number (columns mixing numeric and text-stored values), duplicate_lookup_key (lookup-key columns with duplicates), inconsistent_formula_pattern (formula pattern outliers), and missing_formula_pattern (missing copied formulas). Returns a 0–100 health score plus an issue list with severity and fix or review guidance where available.
Is the SheetBrain health check actually free?
Yes. The deterministic scan runs no AI calls, so it has no quota and is unlimited on every plan including the free tier. Pro ($9/mo) is for the AI side of the product (Generate, Debug, Repair).
How is this different from Find & Replace for #REF!?
Find & Replace catches visible error tokens one search at a time. Detector Set v0.4 catches common visible formula errors, mixed-type columns where SUMIFS quietly excludes text cells, duplicate VLOOKUP keys, formula pattern outliers, missing copied formulas, and lookup formulas whose column or row index exceeds the referenced range — structural defects Find & Replace cannot detect by string match.
Does this work on free Gmail accounts?
Yes. SheetBrain runs on free Gmail™ identically to paid Google Workspace. Gemini for Workspace requires a paid Workspace subscription; SheetBrain does not.
What does the health score mean?
0 to 100. The score starts at 100 and drops 15 per error finding and 5 per warning finding, with a floor at 0. =SHEETBRAIN_HEALTH(A1:Z1000) returns this as a string like "87 — 2 issues" or "100 — All clear ✓". Pass NOW() as a second argument to force a refresh.
Does Check catch formula drift after columns move or get renamed?
No. Detector Set v0.4's deterministic Check tab includes conservative same-column formula-pattern outlier and missing-copied-formula checks, but it does not include schema drift or formula-drift detection after columns move or get renamed. SheetBrain's Repair tab handles that case separately, by comparing the active sheet to a captured schema snapshot and proposing safe formula rewrites. Repair is part of the $9/mo Pro plan.
Does the public audit report show my data?
No. The public report page lists issue types, severity counts, and sheet names, plus generic descriptions of each finding. It never includes raw formulas, cell values, or column headers. Privacy guarantees are documented in the Spreadsheet Trust Standard v0.1.