CalcaTools

JSON, YAML and XML Formatter | Validate and Convert Data

Format, validate, and inspect JSON, YAML, or XML directly in your browser without uploading anything. Indent messy documents, catch syntax errors with clear messages, and keep sensitive configuration local — the developer's daily helper for data files and API payloads.

Last updated: August 2026 · Free · No sign-up required

Format, validate, and inspect JSON, YAML, or XML directly in your browser without uploading source content.

How this tool works

How formatting and validation work

JSON is parsed with the browser’s JSON parser, XML is parsed with the browser’s XML parser, and the formatter then emits readable output. The current YAML mode handles simple key-value documents and is intentionally conservative.

Privacy and limits

Processing occurs in the browser. Do not rely on a web formatter for secrets, and validate the final output with the target application because dialect-specific YAML and XML rules may differ.

Worked example

Enter representative inputs, review the result, and adjust assumptions to compare scenarios.

Frequently asked questions

Does this formatter upload my data?

The formatter is designed to process content in your browser and does not need to upload the pasted data to format it.

Which formats are supported?

The tool supports JSON, XML, and a conservative simple YAML mode. Complex YAML features should be checked with a full YAML parser.

How do I validate JSON?

Choose JSON and format the document. If parsing fails, the browser reports an error instead of producing formatted output.

Can I convert JSON to YAML?

The current mode formats simple YAML key-value content; full cross-format conversion may require a dedicated parser for nested and typed YAML.

Why does XML formatting preserve some declarations?

The browser XML serializer preserves the parsed document structure and may normalize whitespace or declaration details.

Can I paste passwords or API keys?

Avoid pasting secrets into any online tool. Use local development tooling for confidential credentials even when client-side processing is intended.

Quick reference

FormatKey SyntaxBest For
JSON{ "key": "value" }APIs, configs, data exchange
YAMLkey: value (indentation-based)Config files, readability
XML<key>value</key>Documents, legacy systems

swap_horiz Format conversion

JSON, YAML, and XML in one click.

bug_report Error pinpointing

Malformed input is explained.

lightbulb Pro tip

Use the compact mode for payloads.

lightbulb Worked example

Cleaning up a minified JSON API response for debugging.

Result: Readable, indented, valid JSON ready for inspection.

Formula & methodology

Formula: formatted output preserves the parsed data structure while applying readable indentation and syntax rules

How formatting and validation work

JSON is parsed with the browser’s JSON parser, XML is parsed with the browser’s XML parser, and the formatter then emits readable output. The current YAML mode handles simple key-value documents and is intentionally conservative.

Privacy and limits

Processing occurs in the browser. Do not rely on a web formatter for secrets, and validate the final output with the target application because dialect-specific YAML and XML rules may differ.

Authoritative source: JSON specification overview

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