Free Online Developer Tools
Everyday utilities for developers, designers and site owners that run instantly in your browser. Paste API responses, tokens, configs and stylesheets without worrying — the regex tester, JWT debugger, HMAC and webhook signature checker, hex and binary converters, hash generator and cron tool never send data to a server — measure screens and screenshots pixel by pixel with a calibrated screen ruler, and check any domain’s DNS records from public DNS servers worldwide.
23 tools · free · no sign-up
JSON Formatter & Validator
Format, validate, minify and repair JSON online. Get the exact line and column of every error, a collapsible tree view and sorted keys — private, in-browser.
XML to JSON Converter
Convert XML to JSON and JSON to XML online. Keeps attributes, arrays and leading zeros intact, shows exact error lines and never uploads your data.
DNS Lookup
Free DNS lookup: check A, AAAA, CNAME, MX, NS, TXT, SOA and CAA records of any domain, see SPF and DMARC, and do reverse DNS for an IP address.
DNS Propagation Checker
Check DNS propagation worldwide: see the A, CNAME, MX, NS or TXT answer from 7 public DNS networks and 18 ISPs in 15 countries, and track the change.
JSON to CSV Converter
Convert JSON to CSV for Excel or Google Sheets: nested objects become columns, lists are kept and big numbers stay exact. Also CSV to JSON. No upload.
CSV to JSON Converter
Convert CSV or data pasted from Excel to JSON: auto-detected delimiter, real numbers and true/false, nested objects from dotted columns. Free, no upload.
UUID Generator
Generate UUIDs (GUIDs) online: random v4, sortable v7, v1, and name-based v5 and v3 — one or 10,000 at a time. Also decode and validate any UUID.
URL Encoder / Decoder
Encode or decode URLs and query strings online: %20, + and UTF-8 (Hindi, emoji) done right, errors pinpointed, and URL parameters shown in a table.
Base64 Encoder & Decoder
Encode text or files to Base64 and decode Base64 back — UTF-8, URL-safe Base64URL, data URLs for images, file type detection. Free, private, no upload.
Markdown Live Previewer
Write Markdown with a live preview: GitHub tables, task lists, alerts and highlighted code. Export to HTML or PDF — free, private, runs in your browser.
JSON to XML Converter
Convert JSON to XML online: attributes, text, arrays and nested data, with a root element, CDATA and pretty or minified output. Free and private, no upload.
Cron Expression Generator
Build and explain cron expressions in plain English with next run times. Supports Linux crontab, Quartz, Spring and AWS EventBridge, and converts between them.
CSS to Tailwind Converter
Convert CSS to Tailwind classes online: hover, media queries, dark mode and gradients become variants, colours match the palette. Tailwind v4 and v3, free.
Hash Generator
Generate MD5, SHA-1, SHA-256, SHA-512, SHA-3, BLAKE3, CRC32 and HMAC hashes of text or files, and verify checksums. Free, fast and private — no upload.
CSV to Interactive Chart
Turn CSV or Excel data into an interactive bar, line, area, pie or scatter chart online. Group and sum rows, hover for values, download PNG or SVG. No upload.
JWT Debugger
Decode any JWT and verify its signature in your browser: header, claims and expiry explained; HS256, RS256, ES256 and EdDSA with PEM or JWK keys. No upload.
JWT Encoder
Create and sign JWTs in your browser with HS256, RS256, PS256, ES256 or EdDSA: edit claims, set expiry, generate keys and a JWKS. Keys never leave your device.
Markdown to HTML Converter
Convert Markdown to clean HTML online: GitHub tables, task lists and highlighted code, as a snippet or full page, minified or not. Batch files, no upload.
Pixel-Perfect Screen Ruler
Free online screen ruler: a real-size cm and inch ruler calibrated with a bank card, plus pixel-perfect measuring of screenshots with zoom and smart edges.
Regex Tester
Free online regex tester: live match highlighting, groups, replace, a plain-English explanation, unit tests and code for Python, PHP, Java, C# and Go.
Hex to ASCII Converter
Convert hex to ASCII or UTF-8 text and text to hex as you type. Reads 0x, \x and spaced hex, flags bad bytes and shows a hex dump. Free, private, no upload.
Binary to Text Converter
Translate binary code to text and text to binary, live. Handles spaced or joined 8-bit bytes, UTF-8 Hindi and emoji, and flags bad digits. Free and private.
HMAC Generator
Generate HMAC-SHA256, SHA-512, SHA-1 or MD5 in hex or Base64, and verify GitHub, Stripe, Slack, Shopify and Razorpay webhook signatures. Private, no upload.
FAQ
Developer Tools: common questions
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