Each guide starts with what you actually see going wrong, then works through the cause in order. No generic tips lists, no sign-up, and a working tool for messy pasted data.
Pick the symptom that matches yours:
Changing the format does nothing, gives the wrong day/month, or shows a number.
Fix date formats →Often caused by numbers stored as text — the sheet looks right, but formulas ignore the values.
Fix numbers stored as text →Something in the calculation is the wrong type of value. Diagnose it before guessing.
Fix #VALUE! →Extra spaces, invisible characters, blank-looking rows, or duplicates from an import or copy-paste.
Use the data cleaner →Keep the original untouched and get a clean view instead — including fake blanks.
Remove blank rows safely →Conditional formatting not applying, formatting the wrong cells, or shifted by a row.
Run the 6 checks →Paste messy text, remove extra spaces, non-breaking spaces (CHAR 160), invisible characters and blank lines, and optionally remove duplicate lines. It runs entirely in your browser — nothing is uploaded. The cleaned text is still text, so convert numbers or dates in your spreadsheet afterwards if you need them as values.
The spreadsheet equivalent for one cell is =TRIM(CLEAN(SUBSTITUTE(A1, CHAR(160), " "))). Blank-line and duplicate removal have no single-cell equivalent.
A note on verification. The steps on this site describe standard Excel and Google Sheets behaviour. They have not yet been verified against a live Excel 365 / Google Sheets file for this site, and no sample workbooks are published yet — so always work on a copy of your file and check the result before applying a fix to an original. No tested-version badge or date is claimed on any page until that testing is done and recorded.