Data Tools
Format, convert and check your data — private, in your browser
Format and validate JSON, convert CSV and Excel files, and move data between YAML, XML and TOML. 30 free tools that never upload your data — no signup, no limits.
All data tools
Popular tools
- JSON FormatterPretty-print JSON with 2 spaces, 4 spaces or tabs and see exactly where a syntax error is.
- CSV to JSONTurn CSV, TSV or semicolon files into clean JSON with the right types.
- JSON to CSVFlatten JSON arrays and nested objects into rows and columns for a spreadsheet.
- JSON to YAMLTurn JSON into clean, readable YAML with your choice of indent, quoting and key order.
JSON
9 toolsJSON Formatter
Pretty-print JSON with 2 spaces, 4 spaces or tabs and see exactly where a syntax error is.
JSON Minifier
Strip whitespace from JSON to shrink it, and see how many bytes you saved.
JSON Viewer
Explore JSON as a collapsible tree, search keys and values, and copy any path or value.
JSON Compare
Compare two JSON documents structurally and list what was added, removed or changed.
JSON Sort
Sort the keys of a JSON object A to Z or Z to A, recursively, with optional natural order.
JSONPath Tester
Run a JSONPath expression against your JSON and see every match with its path.
JSON to TypeScript
Generate TypeScript interfaces or type aliases from a sample JSON document.
JSON to Java Class
Generate Java POJOs, C# classes or Go structs from a sample JSON document.
JSON Schema Validator
Check JSON data against a JSON Schema and list every error with its path and keyword.
CSV & Excel
8 toolsCSV to JSON
Turn CSV, TSV or semicolon files into clean JSON with the right types.
JSON to CSV
Flatten JSON arrays and nested objects into rows and columns for a spreadsheet.
CSV to Excel
Turn a CSV into a real .xlsx workbook with a bold, frozen header.
Excel to CSV
Export any sheet of an .xlsx workbook as UTF-8 CSV.
Excel to JSON
Turn an .xlsx sheet, or the whole workbook, into JSON records.
CSV Viewer
View a CSV as a sortable, searchable table with column statistics.
CSV Cleaner
Trim cells, drop duplicates and empty rows or columns, and reorder columns.
CSV Delimiter Converter
Switch a file between comma, semicolon, tab and pipe with correct quoting.
YAML, XML & TOML
7 toolsJSON to YAML
Turn JSON into clean, readable YAML with your choice of indent, quoting and key order.
YAML to JSON
Parse YAML, with anchors and multiple documents, into JSON you can paste anywhere.
YAML Validator
Find every syntax problem in a YAML file at once, then re-format it with consistent indentation.
JSON to XML
Turn JSON into well-formed XML with attributes, repeated elements and safe escaping.
XML to JSON
Convert XML to JSON with attributes kept, repeated tags as arrays and entity expansion blocked.
XML Formatter
Pretty-print or minify XML and check it is well-formed, without reordering attributes or changing text.
TOML ↔ JSON
Convert TOML to JSON or JSON to TOML, with dates, big integers and errors handled clearly.
Other formats
4 toolsJSON to HTML Table
Turn a JSON array into clean, escaped HTML table markup with a live preview.
CSV to Markdown Table
Paste CSV, TSV or spreadsheet cells and get an aligned GitHub-flavoured Markdown table.
JSON to SQL
Generate CREATE TABLE and INSERT statements for MySQL, PostgreSQL, SQL Server or SQLite.
Query String ↔ JSON
Parse URL parameters into JSON, or build an encoded query string from a JSON object.
Generators
2 tools30 tools shown
Workflows
Common jobs, done in a few steps
Turn a spreadsheet into API data
Convert an Excel sheet to JSON, tidy it, then check it against a schema.
Move config between formats
Convert YAML to JSON, edit it, and convert it back.
Clean a messy CSV
Fix the delimiter, remove duplicates, then view the result as a table.
Load JSON into a database
Flatten JSON to CSV or generate INSERT statements directly.
Why Nelstack
Fast, private data tools
Your data never leaves your device
JSON, CSV and spreadsheets are parsed in your browser, so customer lists, API responses and configs are never uploaded or stored.
Handles large files
Heavy conversions run in a background worker with a clear size limit, so the page stays responsive instead of freezing.
Clear errors with line and column
Invalid JSON, YAML or XML points to the exact place that is wrong, in plain language.
Real Excel files
Create and read .xlsx files without Excel installed, with a sheet picker and header options.
No caps or signup
No daily quota, no account and no watermark on anything you convert.
Built for phones too
Input comes first on small screens, with touch-friendly controls and no sideways scrolling.
Looking for another kind of tool?
These live in their own tool areas and work the same private, in-browser way. Hashing and encoding live in Security Tools.
Data Tools FAQ
Are these data tools really free?
Yes. The JSON, CSV, Excel, YAML, XML and TOML tools are free with no signup, no daily limit and no watermark. Use them as often as you like.
Is my data sent to a server?
No. Every tool runs entirely in your browser. Your JSON, CSV rows, spreadsheets and config files are parsed on your device and are never uploaded or stored, so you can use them with customer or internal data.
How large a file can I convert?
Text and spreadsheet files up to about 20 MB are accepted. Heavy conversions run in a background worker so the page stays responsive, and anything above the limit gets a clear message instead of freezing the tab.
Can I create and read real Excel files?
Yes. The CSV to Excel tool downloads a real .xlsx workbook, and the Excel tools read .xlsx and .xls files, let you pick a sheet and treat the first row as headers if you choose. Formulas are read as their stored values.
What happens when my JSON or YAML is invalid?
You get a plain-language message with the line and column where parsing stopped, and nothing is changed or lost. Fix the highlighted spot and the result updates as you type.
Where are hashing, encoding and text tools?
Hashes, Base64 and encryption live in Security Tools, text cleanup and comparison in Text Tools, and converting PDFs to Excel in PDF Tools. All of them also run privately in your browser.