Developer & Data · Column contracts

CSV Schema Contract Checker

Set the rules each column must follow, then see every broken value marked in your table: types, required values, ranges, allowed values and duplicates.

Types
Required
Min and max
Allowed values
Unique
Runs in your browser

Open CSVOpen project

CSV data

Your table, checked

Column rules

Edit the rules as JSON

Column contract

Issues

Types are string, number, integer, boolean and ISO date. Values are checked as CSV text. This is a focused contract checker, not JSON Schema. Up to 1.5 million characters.

Using CSV Schema Contract Checker

Validate CSV columns against an explicit contract with types, required values, numeric ranges, allowed values and uniqueness rules.

Paste your CSV or open a file, or start from the example.
Set each column’s type, required, unique, range and allowed values, or press Suggest rules from data.
Broken values are marked in the table and listed under Issues.
Download the report or the contract, or save a project.

Example

Try the built-in example, inspect validation issues and compare the result after changing one option.

Questions & answers

What does CSV Schema Contract Checker do?

Validate CSV columns against an explicit contract with types, required values, numeric ranges, allowed values and uniqueness rules.

What are the important limitations?

Supported types are string, number, integer, boolean and ISO date. Values are checked as CSV text; this is a focused contract checker, not JSON Schema.

Can I save and reopen my work?

Yes. Save a project JSON file containing your inputs, settings and any imported assets. Projects are limited to 40 MiB. Undo/redo stores up to 20 edits in this session and is not saved in the project. There is no automatic saving.

How do imports and output previews work?

Source text is limited to 1.5 million characters per editor; imported text files are limited to 1.5 MB. Text previews show up to 150,000 characters; downloads include the complete output. Tables show 50 rows per page; CSV files include all rows.