What is a CSV Schema?

A CSV Schema is a JSON file that defines the rules for a valid CSV file: which columns are required, what data type each column must contain, and what constraints apply (value ranges, regex patterns, required fields, currency codes, and more).

Once you have a CSV Schema, you can validate any CSV file against it—catching data quality issues automatically before they reach your database, ETL pipeline, or analytics system. The schema acts as a machine-readable data contract between data producers and consumers.

Why Generate a Schema Automatically?

Writing a CSV Schema by hand is tedious and error-prone, especially for files with many columns. The CSV schema generator in CSV Workbench analyzes your actual data to:

Detect the correct data type for each column based on observed values
Identify constraints like minimum/maximum values, regex patterns, and required fields
Bootstrap schema creation in seconds instead of hours
Ensure the schema accurately reflects your real data, not assumptions

How to Generate a Schema from a CSV File: Step by Step

Step 1: Add Your CSV File to CSV Workbench

Open CSV Workbench at app.csvworkbench.com and add a reference to your CSV file. The application uses the File System Access API to read your file directly from your local file system—no upload required. The file is automatically validated for RFC 4180 compliance when added.

Step 2: Click "Generate Schema"

In the CSV Data Editor, click the Generate Schema button in the toolbar. The WebAssembly-powered schema generator analyzes every row of your CSV file, inferring data types and detecting constraints from the actual values present in each column.

Step 3: Review the Generated Schema

A schema review dialog displays the detected column types, confidence levels, and sample values for each column. You can review and edit the generated schema before saving—adjusting types, adding constraints, or marking fields as required.

Step 4: Save and Use the Schema

Accept the generated schema to save it as a CSV Schema file. Once saved, you can associate it with your CSV file and use it to validate future CSV files of the same format—catching data quality issues automatically on every subsequent file.

What the CSV Schema Generator Detects

The generator supports all 6 CSV Schema data types and detects relevant constraints for each:

Data Type	Detected Constraints
CsvString	Regex patterns, min/max length, required
CsvInteger	Min/max value range, required
CsvDecimal	Min/max value range, precision, required
CsvMoney	ISO 4217 currency code, min/max, required
CsvDateTime	RFC 3339 format, date range, required
CsvBoolean	True/false value variants, required

Using the Generated Schema for Ongoing Validation

Once you have a generated CSV Schema, you can use it to validate any future CSV file of the same format. In CSV Workbench, associate the schema with a CSV file and click Validate Data. The validation engine checks:

Column names and counts match the schema
Every value matches its declared data type
All constraints (ranges, patterns, required fields) are satisfied

The generated schema can also be shared with data providers as a formal data contract—a machine-readable specification that defines exactly what a valid CSV file looks like. This eliminates ambiguity and enables data providers to validate their files before sending.

How to Generate a Schema from a CSV File