Data Conversion Tools
Data Conversion covers the moves between the formats data travels in: JSON from APIs, CSV and Excel from spreadsheets and exports, YAML for configuration, and TypeScript types for the code that consumes all of it. Developers, data analysts and anyone wiring a spreadsheet into an app use these tools to change the shape of data without writing a one-off script.
6 free tools · no sign-up · no ads
All Data Conversion (6)
JSON Formatter
Format, minify, validate and query JSON documentsJSON to TypeScript Generator
Generate TypeScript interfaces from any JSON payloadCSV to JSON
Convert CSV data to JSON formatJSON to YAML
Convert between JSON and YAML formatsExcel to JSON Converter
Convert Excel (.xlsx, .xls) and CSV files to JSON format instantlyData Visualization Tool
Create beautiful charts from CSV data with multiple visualization types
Which tool do I need?
Check whether an API response is valid JSON and pull one field out
The JSON Formatter reports Valid or Invalid as you type, pretty-prints the document and runs JSONPath queries such as $.items[0].id.
Turn a spreadsheet into JSON for a fixture or seed file
Export CSV and use the CSV to JSON Converter, or load the .xlsx directly into the Excel to JSON Converter to keep number and date types.
Write TypeScript types for a JSON payload
Paste a sample with several varied records into the JSON to TypeScript Generator so optional fields and unions can be inferred.
Convert a JSON config into YAML for Kubernetes or CI
The JSON to YAML Converter works in both directions with YAML 1.2 rules and rejects duplicate keys instead of dropping data.
Make a quick chart from a CSV without opening Excel
Paste the CSV into the Data Visualization Tool, choose the X axis and a numeric column, and download the chart as SVG.
About Data Conversion
A typical chain starts with the JSON Formatter, which validates with the same JSON.parse your code uses, pretty-prints or minifies, and runs JSONPath queries to pull one field out of a large response. From there the JSON to TypeScript Generator infers interfaces from a sample, the JSON to YAML Converter produces YAML 1.2 for a config file, and the CSV to JSON Converter works in both directions for spreadsheets. The Excel to JSON Converter reads .xlsx and .xls directly, keeps numbers as numbers and turns date cells into ISO 8601 strings. The Data Visualization Tool draws a bar, line, scatter or other chart from a CSV and exports it as SVG.
Each conversion has a point where data can change quietly, and the tools call these out rather than hide them. JSON integers above JavaScript's safe-integer limit (2^53 - 1) can lose precision and a repeated key keeps only its last value. YAML comments do not survive conversion to JSON, and YAML 1.1 readers may treat an unquoted no as false. CSV values stay strings, so leading zeros survive but numbers need converting in your code. Excel formulas are not recalculated; the value saved in the file is used. Generated TypeScript types are only as complete as the sample you gave. All of these tools run in the browser, and the Excel converter accepts files up to 10 MB.
Guides
- JSON Formatting, Validation and JSONPath: A Practical GuideWhy JSON breaks, how to read parser errors, when to minify, and how JSONPath queries save you from scrolling through 4,000-line API responses.
- Converting CSV to JSON (and Back) Without Losing DataCSV looks simple until a comma shows up inside a field. A practical guide to RFC 4180, headers, types and the edge cases that break naive converters.
- JSON vs YAML: Differences, Gotchas and When to ConvertYAML is a superset of JSON with indentation, comments and a few famous traps. Learn how the two map onto each other and what to check after converting.
- Excel to JSON: Dates, Empty Cells and Other Spreadsheet TrapsWhy Excel dates turn into numbers like 45306, how empty cells and merged cells should look in JSON, and a checklist for getting clean data out of a spreadsheet.
Frequently asked questions
Should my data be JSON, CSV or YAML?
It depends on who reads it. JSON suits APIs and nested data that code consumes. CSV suits flat tables that people open in spreadsheets or load into databases. YAML suits configuration that people edit by hand, because it allows comments and is easier to read, at the cost of stricter indentation rules.
Why did numbers or dates change after converting my data?
Each format represents types differently. JSON has one number type and loses precision above 2^53, CSV has no types so everything stays a string, Excel stores dates as serial numbers that the converter turns into ISO 8601 strings, and YAML 1.1 readers can turn unquoted words like no into booleans. Check those fields after any conversion.
Can I convert nested JSON to CSV columns?
Only the top level becomes columns. CSV is flat, so the JSON to CSV direction writes nested objects and arrays as JSON text inside a single cell. If you need each nested field as its own column, flatten the objects in code before converting.
Do the data conversion tools upload my files?
No. CSV, YAML and JSON are parsed in your browser, and Excel files are read locally with the SheetJS library. Nothing you paste or open in this group is sent to a server.
What is the difference between valid JSON and JSON that matches a schema?
Valid JSON means the text parses: brackets balance, keys are double-quoted and there are no trailing commas or comments. Matching a schema means the parsed data has the required fields and types. The JSON Formatter checks syntax only, so a document can pass it and still be missing a field your API expects.