# Developer Tools > Free developer tools: format and validate JSON, test REST APIs, generate QR codes, encode Base64, and more. Everything runs locally in your browser — no signup. - **Category page:** https://www.toolnova.org/dev-tools - **Tools:** 24 - **Price:** Free · No signup · Browser-based ## Tools in this category - [Live HTML Editor](https://www.toolnova.org/dev-tools/html-editor) — Write HTML and see the live preview instantly. Responsive device widths, Monaco syntax highlighting, Prettier formatting, autosave, copy and one-click HTML/PDF export — free, no signup. Markdown: https://www.toolnova.org/dev-tools/html-editor.md - [REST API Tester](https://www.toolnova.org/dev-tools/api-tester) — Test REST APIs in your browser. Send GET/POST/PUT/PATCH/DELETE with query params, custom headers, Bearer/Basic/API-key auth, and inspect response headers, status, timing & size — a free Postman alternative. Markdown: https://www.toolnova.org/dev-tools/api-tester.md - [QR Code Generator](https://www.toolnova.org/dev-tools/qr-generator) — Generate QR codes for URLs, WiFi passwords, contact cards, and text. Add custom logos, choose colors, and download as SVG or PNG — free, no signup. Markdown: https://www.toolnova.org/dev-tools/qr-generator.md - [Barcode Generator](https://www.toolnova.org/dev-tools/barcode-forge) — Generate professional barcodes online. Create CODE128, EAN-13, UPC-A, and CODE39 barcodes and download as SVG or PNG — free, no server upload. Markdown: https://www.toolnova.org/dev-tools/barcode-forge.md - [JWT Decoder & Generator](https://www.toolnova.org/dev-tools/jwt-forge) — Decode, verify, and generate JWT tokens online. Inspect payload claims with human-readable timestamps, detect expiry, verify HS256/HS384/HS512 signatures, and create signed tokens — all locally in your browser. Markdown: https://www.toolnova.org/dev-tools/jwt-forge.md - [JSON to CSV Converter](https://www.toolnova.org/dev-tools/json-csv-converter) — Convert JSON to CSV or CSV to JSON online. Flattens nested objects & arrays, unions all keys, supports comma/semicolon/tab/pipe delimiters and type inference — free, live, runs locally. Markdown: https://www.toolnova.org/dev-tools/json-csv-converter.md - [JSON Formatter](https://www.toolnova.org/dev-tools/json-formatter) — Format, validate, and minify JSON code online. Instantly prettify messy JSON, fix syntax errors, and explore data in tree view — free, no signup. Markdown: https://www.toolnova.org/dev-tools/json-formatter.md - [Base64 Image Encoder](https://www.toolnova.org/dev-tools/base64-image) — Convert images to Base64 strings for embedding in CSS or HTML. Generate data URIs for icons and logos without external HTTP requests — free, local processing. Markdown: https://www.toolnova.org/dev-tools/base64-image.md - [CSS Generator](https://www.toolnova.org/dev-tools/css-forge) — All-in-one CSS generator with 21 tools: triangle, arrow, gradient, box-shadow, glassmorphism, neumorphism, loader, tooltip, clip-path, filter, transform, animation, flexbox, grid & variables — live preview, copy & download, free. Markdown: https://www.toolnova.org/dev-tools/css-forge.md - [SVG Generator & Optimizer](https://www.toolnova.org/dev-tools/svg-forge) — All-in-one SVG toolkit: wave, blob, pattern, polygon, spiral & star generators plus SVG optimizer, minifier, cleaner, path editor, color replacer & sprite generator — live preview, copy & download, free. Markdown: https://www.toolnova.org/dev-tools/svg-forge.md - [Developer Utilities](https://www.toolnova.org/dev-tools/dev-utilities) — Essential developer tools in one place. URL encode/decode, Base64 text conversion, and live Regex testing — all running locally in your browser. Markdown: https://www.toolnova.org/dev-tools/dev-utilities.md - [UUID Generator](https://www.toolnova.org/dev-tools/uuid-generator) — Free UUID generator for v4, v7 and NIL. Create unique identifiers in bulk with uppercase, hyphen-free and brace options, then copy or download — runs locally, no signup. Markdown: https://www.toolnova.org/dev-tools/uuid-generator.md - [Hash Generator](https://www.toolnova.org/dev-tools/hash-generator) — Free online hash generator. Create MD5, SHA-1, SHA-256, SHA-512, SHA-3 and RIPEMD-160 checksums, HMAC signatures and verify hashes — computed locally in your browser, no signup. Markdown: https://www.toolnova.org/dev-tools/hash-generator.md - [Unix Timestamp Converter](https://www.toolnova.org/dev-tools/timestamp-converter) — Free Unix timestamp converter. Convert epoch time to date and date to timestamp in seconds or milliseconds, with UTC, local and ISO 8601 output — runs locally. Markdown: https://www.toolnova.org/dev-tools/timestamp-converter.md - [Cron Expression Generator](https://www.toolnova.org/dev-tools/cron-generator) — Free cron expression generator and explainer. Build cron schedules, read them in plain English, use common presets and preview the next run times — no signup. Markdown: https://www.toolnova.org/dev-tools/cron-generator.md - [Color Contrast Checker](https://www.toolnova.org/dev-tools/color-contrast-checker) — Free WCAG color contrast checker. Test text and background colors for AA and AAA accessibility compliance with a live contrast ratio and preview — hex or RGB. Markdown: https://www.toolnova.org/dev-tools/color-contrast-checker.md - [Hex RGB HSL Color Converter](https://www.toolnova.org/dev-tools/color-converter) — Free color converter: HEX to RGB, RGB to HEX, plus HSL, HSV, CMYK and alpha. Live sliders, color picker, EyeDropper, saved swatches, harmonies, WCAG contrast, colour-blindness preview and code export — no signup, runs locally. Markdown: https://www.toolnova.org/dev-tools/color-converter.md - [Redirect Generator](https://www.toolnova.org/dev-tools/redirect-generator) — Free redirect generator. Convert old→new URL pairs into Nginx, Apache .htaccess, Netlify or Vercel redirect rules with 301 or 302 codes — copy or download. Markdown: https://www.toolnova.org/dev-tools/redirect-generator.md - [JSON to TypeScript](https://www.toolnova.org/dev-tools/json-to-typescript) — Free JSON to TypeScript converter. Generate interfaces or types from JSON with nested objects, arrays and unions inferred automatically — copy the result, no signup. Markdown: https://www.toolnova.org/dev-tools/json-to-typescript.md - [URL Encoder / Decoder](https://www.toolnova.org/dev-tools/url-encoder-decoder) — Free URL encoder & decoder. Percent-encode or decode URLs and query strings with encodeURIComponent or encodeURI, and inspect query parameters — instant, no signup. Markdown: https://www.toolnova.org/dev-tools/url-encoder-decoder.md - [Regex Tester](https://www.toolnova.org/dev-tools/regex-tester) — Free online regex tester. Write JavaScript regular expressions and see live highlighted matches, capture groups, flags and a replace preview — instant, no signup. Markdown: https://www.toolnova.org/dev-tools/regex-tester.md - [User Agent Parser & Display](https://www.toolnova.org/dev-tools/user-agent-parser) — Parse any user-agent string and display the browser, engine, OS, device and bot details instantly. Colour-coded UA anatomy, headless/automation detection, live Client Hints, inspect your own UA, and export JSON — free, private, runs in your browser. Markdown: https://www.toolnova.org/dev-tools/user-agent-parser.md - [WhatsApp Number Checker & Phone Validator](https://www.toolnova.org/dev-tools/whatsapp-phone-checker) — Validate any phone number and build a WhatsApp click-to-chat link, QR code, and vCard — then open it in WhatsApp to confirm the number is registered and view their profile photo. Free, private, no signup. Markdown: https://www.toolnova.org/dev-tools/whatsapp-phone-checker.md - [DNS Lookup](https://www.toolnova.org/dev-tools/dns-lookup) — Look up A, AAAA, MX, TXT, NS, CNAME and SOA DNS records for any domain instantly, resolved live via Google Public DNS — free, no signup. Markdown: https://www.toolnova.org/dev-tools/dns-lookup.md ## FAQ ### Does ToolNova store my code? No. All developer tools, including the HTML Editor and JSON Formatter, process data locally using WebAssembly and Javascript. ### Can I test local APIs with the REST Client? Yes, since the tool runs in your browser, it can reach localhost and internal network endpoints that cloud-based testers cannot. ### Are the QR codes generated in vector format? Yes, the QR Architect allows for high-fidelity SVG exports suitable for professional print and digital branding. ### Can I use the JSON-CSV converter for large datasets? Yes. The converter handles datasets up to several megabytes using streaming JavaScript parsing. For very large files (100MB+), performance depends on your device's memory, but typical API payloads and CSV exports process in milliseconds. ### How does the JWT Forge work without sending tokens to a server? The JWT Forge decodes and validates JSON Web Tokens entirely in your browser using the crypto-js library. It inspects the header, payload, and signature — and you can verify signatures against public keys — all without the token ever touching a network. ### Is the HTML Editor suitable for prototyping production pages? Absolutely. It features Monaco Editor (the engine behind VS Code) with syntax highlighting, autocomplete, and live preview. You can build and test interactive HTML/CSS/JS prototypes directly, then export the code for use in any project. --- ToolNova — https://www.toolnova.org · See https://www.toolnova.org/llms.txt for the full directory.