JSON formatter, JWT decoder, Base64, UUID generator, regex tester and 10+ more tools. Everything runs in your browser. Your data never leaves your machine.
Format, beautify, and pretty-print JSON data with syntax highlighting. Supports large files.
Validate JSON data and get detailed error messages with line numbers. Instant validation.
Minify and compress JSON by removing whitespace. Reduce JSON file size instantly.
Convert JSON arrays to CSV format. Download as .csv file. Handles nested objects.
Convert CSV data to JSON format instantly. Auto-detects delimiters and headers.
Convert JSON to YAML format. Perfect for Kubernetes configs and CI/CD pipelines.
Convert YAML to JSON format. Validates YAML syntax during conversion.
Encode and decode Base64 strings instantly. Supports text and binary data.
Encode and decode URL strings. Handle special characters and query parameters.
Encode and decode URL strings online. Handle special characters, query parameters, and percent-encoding instantly.
Format, beautify, and pretty-print XML online. Auto-indent nested tags, validate structure. 100% client-side.
Format and beautify SQL queries online. Indent SELECT, JOIN, WHERE clauses. Supports MySQL, PostgreSQL, and standard SQL.
Decode and inspect JWT tokens. View header, payload, and verify signature structure.
Generate MD5, SHA-1, SHA-256, and SHA-512 hashes from text. Compare hashes.
Generate random UUID v4 values. Bulk generate and copy multiple UUIDs.
Convert between Unix timestamps and human-readable dates. Supports milliseconds.
Compare two texts and see differences highlighted. Side-by-side or inline view.
Test regular expressions with real-time matching. See matches highlighted with capture groups.
fmt.hjlabs.in is a suite of 15 free online developer tools built for speed, privacy, and simplicity. Every tool runs entirely in your browser on Cloudflare's global edge network, so your data never touches a server. No tracking, no signup, no ads, no limits.
Our free JSON formatter beautifies, validates, and pretty-prints JSON data with syntax highlighting. The JSON validator handles large JSON files efficiently and provides exact line numbers for syntax errors. Use the JSON minifier to compress payloads before shipping. Perfect for debugging API responses, editing config files, and learning JSON.
Convert between formats instantly: JSON to CSV, CSV to JSON, JSON to YAML, and YAML to JSON. Our converters handle nested objects, arrays, and edge cases automatically. Perfect for transforming API data, spreadsheet exports, and Kubernetes configs.
Base64 encode/decode, URL encode/decode, JWT token decoder, and a cryptographic hash generator (MD5, SHA-1, SHA-256, SHA-512) powered by the Web Crypto API. Everything you need for API testing, auth debugging, and security work.
UUID v4 generator, Unix timestamp converter, regex tester with live matching and capture groups, and a side-by-side text diff checker. All the small tools you need every day, in one fast, clean interface.
Powered by Cloudflare Workers for sub-100ms global performance. Part of the hjLabs.in ecosystem — try our OG image generator, AI photo enhancer, DPDPA privacy policy generator, or Arduino image2cpp converter.
Most established online JSON formatters were built in the 2010s, are loaded with display ads, run trackers on every keystroke, and (this is the important one) send your JSON to a server for “processing” that could easily run locally. We rebuilt the whole category for 2026: every tool is a single static page (under 50 KB total), every operation runs in your browser using native APIs, there is no analytics on input data, no signup wall, no rate limit on the page itself, and the source is on GitHub so you can audit exactly what runs. The 15 tools were picked from a list of the most-searched developer utilities, and each one has its own dedicated, indexed page with code examples, gotchas, and links to related tools.
Every single tool on fmt.hjlabs.in — JSON formatter, JSON validator, JSON minifier, JSON↔CSV, JSON↔YAML, Base64 encoder, URL encoder, JWT decoder, SHA-256 / SHA-512 hash generator, UUID generator, Unix timestamp converter, text diff, regex tester — processes your input locally in your browser tab using the standard Web APIs (JSON.parse, btoa/atob, crypto.subtle.digest, crypto.randomUUID, new RegExp). Nothing is uploaded, nothing is logged, nothing is stored. You can put the browser into Airplane Mode after the page loads and every tool keeps working. The only network requests after page load are for Google Fonts (cosmetic) and an optional pageview ping that contains the path you visited and your country code — never the tool input.
Working on Arduino, ESP32, Raspberry Pi Pico, or any embedded project that talks to a backend? These tools pair naturally with our sister site pixel.hjlabs.in (image2cpp — convert PNG/JPG/SVG into C++ PROGMEM byte arrays for SSD1306, ST7735, ILI9341 OLED/TFT displays). Use the JSON formatter for ESPHome / Home Assistant configs, the JWT decoder for AWS IoT Core / Azure IoT Hub tokens, the hash generator for OTA firmware checksums, and the Base64 tool for LoRaWAN sensor payload decoding.
Building a Next.js / Astro / Remix / SvelteKit site? Combine fmt.hjlabs.in with our og.hjlabs.in sister site (free favicon generator + 1200×630 OG image API with 6 templates — the lightweight Vercel OG alternative). Pretty-print your blog post JSON frontmatter here, generate the social preview there, ship to production.