Findings

Things we ran, and what came back

Not tutorials. Each of these started as a question we could not answer from the documentation, so we wrote the formula into a real spreadsheet and read what Google returned.

2026-07-13 Google Sheets will not run a regex on a date, and the obvious fix hands your pattern 46213 REGEXMATCH refuses numbers outright —
2026-07-12 Google Sheets quietly deletes the umlaut from Müller We ran twenty-four formulas against real names in a live Google Sheet. The engine counts characters correctly, folds Ü to ü correctly, and then refuses to admit that ü is a letter. The correct fix is the one construct that throws an error.
2026-07-11 We deleted one backslash from twelve formulas. Sheets complained about two. A regular expression is mostly backslashes, and a backslash is the character least likely to survive a copy and paste. We measured what Google Sheets does when one goes missing. Ten of the twelve broken formulas returned an answer, and one of them returned the letter d.
2026-07-10 We ran sixty regexes from Google Sheets tutorials. All sixty work. We expected to find the internet's Google Sheets regex advice riddled with lookahead and backreferences that a cell would reject. Sixty patterns from twenty-nine pages, every one executed in a live sheet. Not one failed. What breaks is not the advice — it is the delivery, and Sheets tells you nothing useful when it does.
2026-07-09 IFERROR is hiding a broken regex in your spreadsheet An invalid pattern returns