Code Testing — 11 Free Online Tools
11 free online code testing. No signup required.
Test and validate code: regex patterns, JWT tokens, grammar, text diffs, math problems, and typing. Free developer tools for everyday coding tasks.
Need a JSON formatter online or an image compressor free? DevTools Hub has both, plus 278 free online developer tools that run entirely in your browser. Code Testing are free online developer tools you can use instantly — no signup, no upload, 100% private. Popular free tools in this category include a free online regex tester, a JWT decoder and verifier, a grammar checker, or a text diff tool — all free to use online, no signup required. DevTools Hub is a collection of 278 free online developer tools that run entirely in your browser — no signup, no upload, no watermark. Popular tools across the whole site include a free JSON formatter online, a free image compressor free, a free online video compressor, and a free online calculator.
Code Minifier & Beautifier - JS, CSS, HTML
Free online code minifier and beautifier. Minify JS, CSS, HTML for production or beautify for debugging. Size stats, copy, all in browser. No signup.
cURL to Code Converter - Python, Node, Go, PHP, C#
Convert curl commands to Python, Node, Go, PHP, C# code. Deterministic parser, 100% in-browser, no upload, no signup.
Free Grammar Checker - AI Error Explanation
Free AI grammar checker that not only corrects your English but explains why it's wrong. Perfect for learning proper grammar rules.
Free Online Math Solver - Step-by-Step Solutions
Free online math solver with step-by-step solutions. Solve algebra, equations, fractions, and more. No signup required, instant results.
Free Text Diff Checker - Compare Text & Code Online
Free online text diff checker to compare text and code. Side-by-side view with syntax highlighting. Compare JSON, XML, code files and find differences.
Free Typing Test - WPM, Accuracy & Code Mode
Free online typing test with WPM, accuracy, and code snippet modes (JavaScript, Python, SQL, HTML). No signup. Practice common words, quotes, numbers, and programming syntax. Privacy-first.
HTML Playground - Live HTML CSS JS Code Editor with Preview
Free online HTML playground with live preview. Write and test HTML, CSS, and JavaScript instantly. No signup, 100% private browser processing. AI cannot run your code - we do.
JavaScript Obfuscator - Protect JS Code Online
Free online JavaScript obfuscator. Protect JS source code with variable renaming, string encryption, control flow flattening, dead code injection, debug protection, and self-defending. 100% private browser, no signup. AI cannot reliably obfuscate JS - we use a deterministic engine.
JWT Decoder - Decode & Verify Tokens
Free JWT decoder and token inspector. Decode JSON Web Tokens, inspect claims, verify payload data and JWT format. 100% browser-based, no signup.
JWT Generator - Create Signed Tokens Online
Free JWT generator. Create signed JSON Web Tokens with HS256, HS384, HS512 algorithms using Web Crypto API. No signup, no upload, 100% private browser processing. AI cannot generate valid signed JWTs - we do.
Regex Tester - Test Regular Expressions
Test regular expressions with real-time matching. Supports g, i, m, s flags. See match count and captured groups.
Frequently Asked Questions
4 Q&AWhat can I test with the code testing tools?
You can validate regular expressions against sample text, decode and verify JWT tokens (HS256/RS256), check grammar, diff two text blocks, solve math problems step-by-step, and measure typing speed. All eight tools are free, no signup.How does the regex tester work?
Paste a regex and a test string; the tool highlights all matches in real time and reports capture groups, indices, and flag behavior (global, case-insensitive, multiline). Patterns execute in your browser using the JavaScript RegExp engine.Is the JWT decoder safe to use with real tokens?
Yes for inspection: decoding only reads the header and payload, it does not verify the signature. Do not paste tokens containing highly sensitive claims (PII, secrets) into any third-party site; for production verification, use a library in your own backend.Do these tools require an account or API key?
No. All eight code-testing tools run client-side with no server API calls and no signup. You can use them offline once the page is loaded.How to Use These Code Testing Tools
guideEvery code testing tool below runs entirely in your browser — no signup, no upload, no watermark. To find a specific tool, type a name, keyword, or scenario into the search box and the list filters instantly. Popular code testing tools are linked in the summary at the top; click any card or link to open the tool and follow the on-screen instructions. Hover any tool card to read its full description, then click its name or button to open it.