CSV Data Type Guesser

CSV Data Type Guesser is a free online tool that works entirely in your browser — no signup, no data uploaded, no limits.

Guessing Column Types Is the First Step of Every Import

Before a CSV becomes a database table, somebody has to decide what type each column should be. Is the signup_date column a real date or just a text string that looks like one? Is is_active stored as the word "true" or as a 1 and 0? Get this wrong and your import either fails outright or succeeds while quietly storing everything as the wrong type, which causes calculation and sorting bugs much later.

This tool examines every value in each column and matches it against pattern rules for dates, booleans, numbers, and emails, falling back to plain text when nothing else fits. The result tells you not just the guessed type but how confident that guess is, based on what percentage of values in the column actually matched the pattern.

Why Pattern Order Matters

A value like "20240115" could be read as a large number or a date in compact format. The detection checks date patterns first because dates have more distinctive structure, then falls through to boolean and numeric checks, and only classifies as generic text if nothing more specific matches. This ordering avoids common misclassifications.

Using Confidence Percentage to Spot Dirty Columns

A column detected as Number with 98% confidence is clean and ready to import as a numeric field. A column detected as Number with only 70% confidence means roughly three in ten values do not fit the pattern — worth investigating before you commit to that column type, since those mismatched values will likely cause import errors.