Data Format Converters
Convert between the data formats developers use every day — JSON, YAML, CSV, XML, Markdown, and TypeScript. Every converter runs 100% in your browser, so nothing is ever uploaded to a server.
JSON to YAML Converter
Convert JSON to YAML and YAML back to JSON, with a one-click direction swap.
Open JSON ↔ YAML →JSON to CSV Converter
Turn a JSON array into CSV for spreadsheets, or parse CSV into clean JSON.
Open JSON ↔ CSV →XML to JSON Converter
Convert XML to JSON and JSON back to XML, preserving attributes and nested structure.
Open XML ↔ JSON →Markdown to HTML Converter
Convert Markdown to clean HTML with a live preview, powered by a fast CommonMark parser.
Open Markdown → HTML →JSON to TypeScript
Generate TypeScript interfaces from a JSON sample, with nested types inferred automatically.
Open JSON → TS →What are data format converters?
A data format converter takes structured data written in one format and re-expresses it in another, without changing the underlying meaning. The same list of users might live in a .json API response, a .yaml config file, a .csv spreadsheet export, or an .xml document — converters move data between these representations so you can use whichever one a given tool, language, or teammate expects.
Formatly's converters cover the most common interchange paths in modern development:
- JSON ↔ YAML — switch between the format APIs return and the format that powers Kubernetes, CI pipelines, and app configs. Bidirectional, with a one-click direction swap.
- JSON ↔ CSV — turn a JSON array of objects into spreadsheet-ready CSV for Excel or Google Sheets, or parse a CSV export back into clean JSON. Bidirectional.
- XML ↔ JSON — convert legacy or SOAP/RSS-style XML into JSON your code can consume, or build XML from JSON. Element attributes and nesting are preserved.
- Markdown → HTML — render Markdown into clean HTML with a live preview. This conversion is one-way.
- JSON → TypeScript — generate
export interfacedeclarations from a JSON sample so you get static typing for API payloads. This conversion is one-way.
When and why you convert formats
You usually convert when two systems prefer different shapes for the same data:
- Configuration: tooling that emits JSON often needs to become YAML for a Kubernetes manifest, Docker Compose file, or GitHub Actions workflow — and back again for programmatic editing.
- Spreadsheets and reporting: stakeholders want CSV they can open in a spreadsheet, while your code wants JSON. Converting bridges the two.
- APIs and integration: a partner returns XML but your service speaks JSON, so you convert at the boundary.
- Documentation: Markdown is easy to write, but websites, emails, and CMS fields need HTML.
- Typing: turning a sample JSON response into TypeScript interfaces gives you autocomplete and compile-time safety with no hand-written types.
Lossless, structure-preserving, and private
Where the source and target formats can both express the same structures, these conversions are structure-preserving — keys, nesting, arrays, and scalar values map across faithfully, and JSON ↔ YAML, JSON ↔ CSV, and XML ↔ JSON are reversible. Some conversions are inherently one-way: Markdown → HTML and JSON → TypeScript generate new artifacts (rendered markup and type declarations) and are not designed to round-trip back. Tabular CSV also flattens deeply nested JSON, so a JSON array of flat objects converts most cleanly.
Every converter is 100% client-side. Your data is parsed and transformed entirely in your browser using JavaScript — it is never uploaded, logged, or stored on a server. That makes these tools safe for proprietary configs, internal API payloads, and sensitive spreadsheet exports, and means they keep working even after your connection drops.
Guides
Learn the concepts behind these tools:
Data Format Converters FAQ
What is the difference between a data format converter and a formatter?
A formatter re-indents data that stays in the same format — for example, beautifying messy JSON into readable JSON. A converter changes the format itself, such as turning JSON into YAML, CSV, XML, or TypeScript. Formatly offers both as separate tools.
Are these conversions lossless?
Where both formats can represent the same structures, yes — JSON ↔ YAML, JSON ↔ CSV, and XML ↔ JSON are structure-preserving and reversible. CSV is tabular, so deeply nested JSON flattens best when it is an array of flat objects. Markdown → HTML and JSON → TypeScript are intentionally one-way — they generate rendered HTML and type declarations rather than round-tripping.
Is my data uploaded to a server when I convert it?
No. Every converter is 100% client-side, running entirely in your browser. Your JSON, YAML, CSV, XML, or Markdown is never sent to, stored on, or seen by any server, so it is safe to use with confidential configs, internal API responses, and sensitive data.
Why is Markdown to HTML one-way?
Converting Markdown to HTML renders your text into the final markup a browser displays, and there is no single, unambiguous way to reconstruct the original Markdown from arbitrary HTML. Formatly shows the generated HTML source alongside a live preview, but it does not convert HTML back to Markdown.
Do XML to JSON conversions keep attributes and nested structure?
Yes. The XML ↔ JSON converter preserves nested elements and element attributes (attributes are mapped to JSON keys with an @_ prefix) so the document structure survives the round trip. You can convert XML to JSON to inspect or process it, then build XML back from JSON.
Can I generate TypeScript types from a JSON response?
Yes. The JSON → TypeScript tool infers export interface declarations from a JSON sample: nested objects become their own interfaces, arrays of objects are merged into one shape, keys missing from some items become optional, and mixed value types become unions — all locally in your browser.
Do these converters work offline?
Once the page has loaded, conversions run locally with no further network requests, so the tools keep working even if your connection drops. Nothing leaves your device at any point.