JSON Converter
Convert JSON to CSV, YAML, TypeScript interfaces or JSON Lines — and back again. Everything runs locally in your browser, so the data you paste is never uploaded.
Input
Conversion
Output
CSV flattens nested objects into dot-columns. TypeScript merges array element shapes and marks inconsistent keys optional.
About ALT JSON Converter
ALT JSON Converter is a fast, private tool for turning JSON into the format you actually need — and turning other formats back into JSON. It runs entirely in your browser. We built it because most online converters quietly upload whatever you paste to a server before handing anything back, which is a problem the moment your data contains anything you'd rather keep to yourself. This page never sends your data anywhere.
Pick a conversion, paste your data, and hit convert. There's nothing to install and no account to create. Output appears instantly, ready to copy or download as a file.
Convert JSON to CSV
Drop in a JSON array of objects and get a clean CSV you can open in Excel, Google Sheets or Numbers. Nested objects are flattened into dot-notation columns like address.city, and any keys that only appear on some rows still get their own column, so nothing is silently dropped. Going the other way, CSV to JSON reads your header row and turns each line into an object, guessing numbers, booleans and nulls so you don't end up with everything stuck as a string.
Convert JSON to YAML
Need a config file or a Kubernetes manifest? JSON to YAML produces tidy, properly indented YAML with sensible quoting — strings that could be misread as numbers, booleans or dates are quoted automatically, so the result stays valid. It handles nested objects and arrays the way you'd expect.
Generate TypeScript types from JSON
Paste a sample API response and JSON to TypeScript writes the interfaces for you. It walks the whole structure, merges the shapes of objects inside an array into one interface, marks keys that aren't always present as optional, and reuses identical shapes instead of repeating them. It's a real time-saver when you're wiring up a new endpoint and don't want to hand-type a dozen interfaces.
JSON and JSON Lines (JSONL)
Working with logs, datasets or streaming records? JSON to JSONL turns an array into one object per line, and JSONL to JSON collects those lines back into a single array. Both directions are one click.
Your data never leaves the page
Everything you paste is converted right here in your browser and is never uploaded. We use privacy-respecting, consent-based analytics to see which tools are useful, but the data you convert is never transmitted, so you can safely work with access tokens, internal payloads or production data. The conversions themselves keep working even with your Wi-Fi switched off.
Looking for more than conversion? The companion JSON Formatter & Editor formats, validates, repairs, explores and diffs JSON in the same private, in-browser way.
Frequently asked questions
Is ALT JSON Converter free?
Yes. Every conversion is free, with no limits, sign-up or paywall.
Do you see or store the data I paste?
No. Nothing is uploaded or saved anywhere. Your data lives only in the browser tab and is gone the moment you close it.
Does it work offline?
It does. Once the page has loaded you can disconnect completely and every conversion still runs.
What can it convert?
JSON to CSV, YAML, TypeScript interfaces and JSON Lines, plus CSV to JSON and JSONL to JSON.