# Check the data type of every column

> Drop a CSV or Excel file. Each column gets a type, a confidence score and the cells that break the pattern.

Find each column’s data type and the cells that do not fit: mixed date formats, letter O for zero, lost leading zeros. Runs in your browser.

- Tool: [Data type checker](https://fixmint.cc/data-type-checker)
- Category: [Spreadsheets & data](https://fixmint.cc/spreadsheets)
- Fixes: Column has mixed formats
- Runs in the browser: files and text stay on the device, no sign-up, free.

## How to check the data type of each column

1. Drop a CSV or Excel file, or paste rows from a spreadsheet.
2. Read each column card: its type, its confidence and the cells that do not fit.
3. Copy the schema as JSON or as an SQL CREATE TABLE.

## Questions

### How does it decide a column’s type?

It gives every non-empty cell one reading, such as a whole number, a date or an email address. The column takes the reading most of its cells share, and confidence is the share of cells with no problem.

### Why is a date marked ambiguous?

If no date in the column has a first or second part above 12, then 03/04/2025 could be 3 April or 4 March. The tool says the order is ambiguous rather than guess.

### Why do leading zeros matter?

A zip code or an ID such as 01234 loses its zero when a spreadsheet reads it as a number. Keep such columns as text in your database.

### Does it change my file?

No. The file is read in your browser and never uploaded, and nothing is rewritten. The schema is a suggestion to review before you use it.

## Related tools

- [CSV column profiler](https://fixmint.cc/csv-column-profiler): Need stats for every column
- [CSV cleaner](https://fixmint.cc/csv-cleaner): Messy CSV with blanks and copies
- [Anonymize spreadsheet](https://fixmint.cc/anonymize-spreadsheet): Names and emails in a table
- [Excel formula checker](https://fixmint.cc/excel-formula-checker): Workbook has broken formulas