Which types can it detect?

For each column it tests, in order, boolean, integer, float, ISO date, email and phone, falling back to free-text. A column is assigned a type only when at least 80% of its non-empty cells match that type, so a few stray values do not derail the result.

How is confidence calculated?

Confidence is the share of non-empty cells in the column that match the chosen type. A column where 95 of 100 filled cells parse as integers reports the integer type at 95% confidence; the remaining cells are likely typos or missing-value markers.

No. Parsing and inference run entirely in your browser using JavaScript. The CSV you paste — which may contain real customer records — never leaves your machine.

Why is a numeric column reported as float instead of integer?

If a column contains any decimal values alongside whole numbers, it is reported as float so the chosen type can represent every value. A column whose cells are all whole numbers is reported as integer.

How many rows does it look at?

It samples up to 1000 data rows per column, which is plenty to infer a stable type while staying fast in the browser. If your file is larger, the inference is based on that representative sample.

CSV Column Type Inferrer

The CSV Column Type Inferrer reads pasted CSV data and works out the most likely data type of each column — integer, float, boolean, ISO date, email, phone or free-text — with a confidence score. It is a quick way to understand an unknown dataset or bootstrap a database schema, all in your browser.

How it works

First the tool parses the CSV using an RFC-4180-style reader that correctly handles quoted fields containing commas, escaped quotes ("") and embedded newlines. It then samples up to 1000 data rows and classifies each non-empty cell with an ordered set of tests:

boolean — values like true, false, yes, no, t, f
integer — optional sign followed by digits
float — a decimal point with digits
ISO date — YYYY-MM-DD with an optional time component that also parses as a real date
email — a local part, @, and a dotted domain
phone — an optional + and at least seven digits with common separators
free-text — anything else

A column is assigned a type only when at least 80% of its non-empty cells match a single type; otherwise it is reported as free-text. If a numeric column mixes whole numbers and decimals, it is reported as float so every value fits.

Example

A price column containing 19.99, 5 and 12.50 is reported as float (because of the decimals), while an id column of 1, 2, 3 is reported as integer. A signup_date column of 2026-01-15-style values is reported as date.

Notes

Confidence is the fraction of non-empty cells matching the chosen type, so it also hints at data quality — a high-but-not-100% score usually points to a few malformed rows worth investigating. All parsing runs locally, so the tool is safe for sensitive datasets.