Data & File Tools

Free online data tools - JSON to CSV, CSV to JSON, JSON validator, XML to JSON converter.

Free Online Data Conversion Tools - JSON, CSV & XML

Data format conversion is a constant requirement in API development, data analysis, database work, and spreadsheet reporting. These four free tools convert between the most common data interchange formats - JSON, CSV, and XML - instantly in your browser. No file upload to a server, no processing delay, and no size limits for typical use cases. Paste your data, get the converted output, and copy it to where you need it.

JSON to CSV Converter

JSON (JavaScript Object Notation) is the universal format for API responses and modern data storage - but spreadsheet applications like Excel, Google Sheets, and LibreOffice Calc work best with CSV (Comma-Separated Values). The JSON to CSV Converter takes a JSON array of objects and produces a CSV file where the first row contains the column headers (extracted from the JSON object keys) and subsequent rows contain the data values. This makes it easy to take API response data and open it in a spreadsheet for analysis, filtering, pivot tables, and charts. The converter handles nested objects by flattening them with dot notation, and handles arrays within objects by joining their values.

CSV to JSON Converter

The reverse operation - CSV to JSON - is used when you need to import spreadsheet data into a web application, database, or API. The converter reads the header row of your CSV to determine field names, then converts each subsequent row to a JSON object with those field names as keys. Automatic type detection converts numeric strings to numbers and "true"/"false" strings to booleans, so the JSON output is ready to use without further processing. The converter handles various CSV dialects including comma-separated, semicolon-separated (common in European locales where commas are used as decimal separators), and tab-separated (TSV) files.

JSON Validator

Invalid JSON causes application errors that can be difficult to debug, especially in minified or large JSON files where the error position is hard to identify by eye. The JSON Validator checks syntax against the JSON specification (RFC 8259) and reports the exact line and character position of the first error. It detects the most common JSON mistakes: trailing commas after the last item in an object or array (not valid in JSON, though valid in JavaScript), single-quoted strings (JSON requires double quotes), unquoted object keys (JavaScript object syntax, not valid JSON), comments (not supported in JSON), missing commas between items, and mismatched brackets or braces. After validation, it can also format the JSON for easier reading.

XML to JSON Converter

XML (Extensible Markup Language) was the dominant data interchange format before JSON, and is still widely used in enterprise systems, SOAP web services, RSS feeds, configuration files (Maven, Gradle, Spring), and legacy APIs. Converting XML to JSON is necessary when modernising legacy APIs, integrating old enterprise systems with modern REST APIs, processing RSS feeds in JavaScript, or simply working with data that arrives as XML but needs to be used in a JSON context. The converter handles XML attributes (converted to @attribute keys in the JSON), text content, nested elements, and repeated elements (converted to JSON arrays). The resulting JSON preserves the full structure of the XML document.

When to Use Each Data Format

JSON is the best choice for web APIs, JavaScript applications, NoSQL databases (MongoDB, Firestore, DynamoDB), and configuration files in modern applications. It is lightweight, human-readable, and natively supported in all programming languages.

CSV is best for tabular data that will be used in spreadsheets, data analysis tools (Excel, pandas, R), relational database imports, and reporting. It is not suitable for nested or hierarchical data - that would need JSON or XML.

XML remains important for SOAP web services, document formats (DOCX, XLSX are ZIP files containing XML), RSS/Atom feeds, SVG graphics, configuration in Java/Spring ecosystems, and any context where schema validation and namespaces are required.

Frequently Asked Questions

Is my data uploaded to a server when I use these tools?

No. All data conversion processing happens entirely in your browser using JavaScript. The JSON, CSV, or XML you paste into the tool never leaves your device - it is not sent to any server, not logged, and not stored. This is both more private and faster than server-side tools: there is no upload/download round trip, so conversion is instant even for large files. Once the page has loaded, the tools work without any internet connection at all.

What happens to nested JSON objects when converting to CSV?

CSV is a flat, two-dimensional format - it has rows and columns but no nesting. When a JSON object contains nested objects (e.g., an address field that itself contains street, city, and postcode), the converter flattens them using dot notation: address.street, address.city, address.postcode become separate column headers. Arrays within objects are typically joined into a single string value (comma-separated or pipe-separated). For deeply nested JSON with complex arrays of objects, full flattening may not produce the expected result - in those cases, it may be better to pre-process the JSON to extract the specific fields you need before converting.

Why does my JSON fail validation even though it looks correct?

The most common causes of JSON validation failure are: (1) Trailing commas - JSON does not allow a comma after the last item in an array or object. JavaScript objects allow this, but JSON does not. (2) Single-quoted strings - JSON requires double quotes around all strings and object keys. (3) Comments - JSON has no comment syntax; // and /* */ comments are not valid. (4) Unquoted keys - object keys must be quoted strings in JSON. (5) Special number values - NaN, Infinity, and -Infinity are not valid JSON values. The validator identifies the specific error and its location so you can fix it quickly.

How does the CSV to JSON converter handle different delimiter types?

The converter auto-detects the delimiter used in your CSV file. It checks whether the file uses commas (standard CSV, most common in English-locale systems), semicolons (common in European countries where commas are used as decimal separators), or tabs (TSV files, common in database exports and Excel exports). Auto-detection works by analysing the frequency and consistency of these characters in the first few lines. If auto-detection produces the wrong result, you can manually select the delimiter. Quoted fields (fields containing the delimiter character, wrapped in double quotes) are handled correctly.

How are XML attributes handled in the XML to JSON conversion?

XML attributes are preserved in the JSON output using a conventional prefix to distinguish them from child elements. The most common convention is to prefix attribute names with @ - so an XML element <user id="123" status="active"> becomes a JSON object {"@id": "123", "@status": "active"}. Text content within an element is stored as a "#text" key. Repeated elements at the same level (which are valid in XML but have no direct JSON equivalent) are converted to JSON arrays. This ensures that all information from the XML document is preserved in the JSON output, though the resulting JSON structure may look different from a JSON document designed from scratch for the same data.