The Best Free Browser Tools for Node.js Developers
Node.js developers move fast. Whether you're building REST APIs with Express, microservices with NestJS, or real-time apps with Socket.IO, you're constantly handling JSON, tokens, hashes, and encoded strings. The tools at tools.fun are designed to eliminate the small friction points that slow you down — all free, all browser-based, zero install required.
JSON Formatter & Validator
Node.js is the language of JSON. From Express middleware to NestJS interceptors, JSON is everywhere. When JSON.parse() throws a syntax error in production, paste the raw payload here to see exactly where the problem is. The formatter also pretty-prints minified responses so you can read nested objects without squinting.
package.json files after manual edits, and inspecting AWS Lambda event payloads.JSON.stringify() output and use the formatter to verify your objects serialize exactly as expected before sending to a client.Regex Tester
JavaScript regex and Node.js string validation go hand in hand. Whether you're writing input validation middleware in Express or building route pattern matchers, test your regex patterns here against real sample data before committing them to code. The tester supports all JavaScript-compatible flags including g, i, m, and s.
Base64 Encoder / Decoder
JWT tokens are base64url-encoded. HTTP Basic Auth headers are base64-encoded. Buffer-to-base64 conversions happen constantly in Node.js. Use this tool to manually decode JWT segments, inspect auth headers, or verify that your Buffer.from(str).toString('base64') output is correct without running a script.
. separators in a JWT with newlines, then decode each segment separately to inspect header, payload, and signature independently.URL Encoder / Decoder
Node.js's built-in encodeURIComponent() and URLSearchParams handle most URL encoding, but when you're debugging a mangled redirect URL or constructing OAuth callback URLs, a visual encoder is much faster than writing throwaway scripts. This tool handles both encoding and decoding instantly.
WebSocket Tester
Testing WebSocket endpoints without Postman or a custom client script is a pain. The WebSocket tester lets you connect to any ws:// or wss:// endpoint directly from the browser, send JSON messages, and see responses in real time. This is perfect for testing Socket.IO servers, NestJS WebSocket gateways, and custom WebSocket microservices.
Unix Timestamp Converter
JavaScript's Date.now() returns milliseconds while most backend systems use seconds. JWT exp claims use seconds. MongoDB timestamps use milliseconds. The constant mismatch causes bugs. Use the timestamp converter to instantly verify what any epoch value represents and catch off-by-1000 errors before they hit production.
Date.now() vs Math.floor(Date.now()/1000) timestamp differences.Text Diff Tool
Comparing two versions of a package.json, an OpenAPI spec, or a NestJS module configuration is something Node.js developers do constantly during upgrades and refactors. The diff tool shows precise line-by-line changes without needing Git, making it ideal for comparing config snapshots or reviewing auto-generated files.
package-lock.json changes between versions, reviewing auto-generated NestJS boilerplate, and diffing OpenAPI spec files.MD5 Hash Generator
While Node.js's crypto module handles hashing in production, you often need a quick MD5 during development — for cache keys, ETag values, or verifying that two strings produce the same hash. This tool gives you instant results without writing a script or opening the Node REPL.
AES Encryption Tool
Node.js crypto operations for AES encryption require getting IV, key size, and mode exactly right. Use this tool as a reference implementation to verify your Node.js crypto.createCipheriv() output against known-good encrypted values, ensuring your encryption logic is correct before sending sensitive data to production.
Password Generator
Node.js apps need strong secrets for JWT signing, session cookies, and API key generation. Use the password generator to create high-entropy random strings on demand. Generate a 64-character secret for your JWT_SECRET environment variable or a 32-character API key for your service — then store it safely in your secrets manager.
JWT_SECRET values for Node.js services, creating strong session secrets for Express, and producing API keys for internal service authentication.cURL Command Builder
Testing Node.js REST APIs from the command line means writing curl commands. The curl builder lets you construct requests visually — set method, headers, and body, then copy the generated curl command. This is a free alternative to Postman's basic request building, with no account or subscription required.
Character & Word Counter
Writing API documentation, README files, or npm package descriptions requires knowing your character counts. The character counter is especially useful when writing description fields in package.json, composing GitHub Actions workflow names, or sizing notification message payloads for push notification APIs.
The next time you're debugging a Node.js API at 2am and need to quickly decode a JWT, format a JSON error response, or test a WebSocket connection — tools.fun has you covered without leaving the browser. Keep it bookmarked.
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