Data Type Guesser
Paste a CSV table, JSON array, or plain list of values and instantly detect the data type of each column — integer, float, boolean, date, email, URL, UUID, and more. Our data type guesser computes confidence scores, numeric statistics, and generates SQL CREATE TABLE and TypeScript interface output. All analysis runs locally in your browser with no signup required.
Paste a CSV table, JSON array of objects, or a plain list of values. The data type guesser detects the type of each column — integer, float, boolean, date, email, URL, UUID, and more — with confidence scores, SQL types, and TypeScript types. All analysis runs locally in your browser.
Why Use Our Data Type Guesser?
Instant column type detection with SQL and TypeScript output
Instant Data Type Detection
Our data type guesser detects 12 distinct types — integer, float, boolean, date, datetime, time, email, URL, UUID, JSON, null, and string — for every column in your CSV or JSON input. Results appear instantly with per-column confidence scores and type breakdowns.
Secure Data Type Guesser Online
All type detection runs locally in your browser. Your CSV data, JSON arrays, and column values are never uploaded to any server when you use our data type guesser online — 100% private, safe for sensitive business data and PII.
Data Type Guesser — No Installation
Use our free data type guesser directly in your browser with no downloads, no plugins, and no account required. Paste CSV, JSON, or a plain list of values and get instant type detection results — completely free.
SQL and TypeScript Type Generation
Beyond type detection, our data type guesser generates a ready-to-use SQL CREATE TABLE statement and a TypeScript interface from your column results — saving you time when setting up databases or defining data models.
Common Use Cases for Data Type Guesser
Practical applications for automatic column type detection
Database Schema Design
Paste a CSV export and use our data type guesser to instantly get the correct SQL column types for your CREATE TABLE statement — saving hours of manual type inference when designing a new database schema.
API Response Validation
Paste a JSON array from an API response into the data type guesser to verify that field types match your expected schema — catching type mismatches like strings where integers are expected before they reach production.
Data Pipeline Setup
Before importing CSV data into a data warehouse or ETL pipeline, use our data type guesser to detect column types and identify null values, mixed types, and unexpected formats that could cause pipeline failures.
TypeScript Model Generation
Generate a TypeScript interface from any CSV or JSON dataset with one click. Our data type guesser infers the correct TypeScript types — including nullable variants — and outputs a ready-to-use interface definition.
Data Quality Auditing
Use the confidence scores and type breakdown in our data type guesser to spot columns with mixed types — for example, a column that is mostly integers but contains a few string values — indicating data quality issues.
Spreadsheet to Database Migration
When migrating spreadsheet data to a relational database, use our data type guesser to automatically determine the correct column types, null constraints, and SQL data types for each column in your export.
Understanding Data Type Detection
Learn how the data type guesser detects column types and generates schema output
What is a Data Type Guesser?
A data type guesser is a tool that analyzes the values in a data column and infers the most likely data type — such as integer, float, boolean, date, email, or string. This is essential when working with CSV exports, API responses, or spreadsheet data where column types are not explicitly declared. Our data type guesser detects 12 distinct types per column, computes a confidence score based on how consistently values match the detected type, and generates both SQL and TypeScript type suggestions — all running locally in your browser with no server upload required.
How Our Data Type Guesser Works
- Paste Your Data: Paste a CSV table (with or without a header row), a JSON array of objects, a JSON array of primitives, or a plain newline-separated list of values. The data type guesser automatically detects the input format and delimiter.
- Instant Browser-Based Analysis:Click "Detect Data Types" and the tool analyzes every value in every column entirely in your browser. No data is sent to any server. Each column gets a dominant type, a confidence score, a type breakdown, sample values, and numeric statistics where applicable.
- Copy or Download the Output: Switch to the TypeScript Interface or SQL CREATE TABLE tabs to copy or download the generated schema code. Use it directly in your database migration, ORM model, or TypeScript data layer.
What the Data Type Guesser Detects
- Numeric Types: Integers (whole numbers matching
-?\d+) and floats (decimal numbers including scientific notation) are detected separately and mapped toINTEGERorDECIMAL(18,6)SQL types. - Temporal Types: Dates (ISO 8601 and common formats), datetimes (with time and timezone), and times (HH:MM:SS with optional AM/PM) are detected and mapped to
DATE,TIMESTAMP, andTIMESQL types. - Semantic Types: Email addresses, URLs, and UUIDs are detected using pattern matching and mapped to appropriate SQL types (VARCHAR(254), TEXT, UUID) and TypeScript string types.
- Null Handling:Empty strings, the literal text "null", "NA", "N/A", and "-" are all treated as null values. Columns with any null values get a
NULLSQL constraint and a| nullTypeScript union type.
Important Notes on Type Detection Accuracy
The data type guesser uses heuristic pattern matching — it infers types from value patterns, not from a declared schema. A confidence score below 80% indicates a mixed-type columnwhere values do not consistently match a single type. This often signals a data quality issue worth investigating before importing into a database. For ambiguous cases — such as a column containing only "1" and "0" — the guesser may detect boolean or integer depending on the majority pattern. Always review the type breakdown and sample values before using the generated SQL or TypeScript output in production.
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Frequently Asked Questions About Data Type Guesser
Common questions about column type detection, confidence scores, and schema generation
A data type guesser analyzes the values in a data column and infers the most likely data type — integer, float, boolean, date, email, URL, UUID, or string. Our data type guesser runs entirely in your browser, supports CSV, JSON, and plain lists, and generates SQL and TypeScript types from your data — no signup required.
The data type guesser supports CSV tables (with automatic delimiter detection for comma, semicolon, tab, and pipe), JSON arrays of objects, JSON arrays of primitive values, and plain newline-separated lists. The input format is detected automatically.
Yes. All type detection runs entirely in your browser using JavaScript. Your CSV data, JSON arrays, and column values are never uploaded to any server. Everything stays completely private on your device — safe for sensitive business data, PII, and confidential records.
Yes. Our data type guesser is 100% free with no signup, no account, and no usage limits. Analyze as many datasets as you need — completely free, forever.
The confidence score is the percentage of non-null values in a column that match the dominant detected type. A score of 100% means all non-null values are the same type. A score below 80% indicates a mixed-type column — for example, a column that is mostly integers but contains some string values — which often signals a data quality issue.
Empty strings, the literal text "null", "NA", "N/A", and "-" are all treated as null values. Null values are excluded from type detection and confidence scoring. Columns with any null values get a NULL SQL constraint and a "| null" TypeScript union type in the generated output.
Yes. The data type guesser detects ISO 8601 dates (YYYY-MM-DD), common date formats (DD/MM/YYYY, MM/DD/YYYY), ISO 8601 datetimes with timezone offsets, and time values (HH:MM:SS with optional AM/PM). Ambiguous date formats like "01/02/03" may be detected as a date but the exact interpretation depends on your locale.
The data type guesser maps each detected type to a standard SQL type: integers to INTEGER, floats to DECIMAL(18,6), booleans to BOOLEAN, dates to DATE, datetimes to TIMESTAMP, emails to VARCHAR(254), URLs and JSON to TEXT, and UUIDs to UUID. Columns with null values get a NULL constraint; columns without nulls get NOT NULL.
Yes. The generated TypeScript interface uses standard TypeScript types — number, string, boolean, Date, and Record<string, unknown> for JSON columns. Nullable columns get a "| null" union type. Copy the interface and paste it into your TypeScript project as a starting point — you may want to rename the interface and adjust types for edge cases.