Free Online Developer Tools
46 free tools · local processing where applicable · optional network features
- JSON Formatter & Validator
- URL Encoder / Decoder
- JWT Decoder
- UUID Generator
- TXT to JSON Converter
- HTML Formatter
- CSS Formatter
- SCSS Formatter
- JavaScript Formatter
- JavaScript Minifier
- JavaScript Validator
- HTML Validator
- JSON to XML Converter
- Markdown ↔ HTML Converter
- Regex Tester
- Color Picker
- Unicode Converter
- API Request Tester
- URL Parser
- .gitignore Generator
- tsconfig.json Generator
- ESLint Config Generator
- Prettier Config Generator
- Semver Bump Calculator
- Semantic Commit Message Helper
- Doc Comment Generator
- Schema Markup Generator
- Robots.txt Generator
- SEO Analyzer
- Structured Data Tester
- AMP Validator (Basic)
- Meta Description Checker
- Core Web Vitals Checklist
- PWA Checklist
- GDPR Compliance Checklist
- Mobile-Friendly Checklist
- WHOIS Lookup (RDAP)
- Redirect Checker
- Broken Link Checker
- HTML Preview
- Responsive Screen Tester
- Browser Compatibility Checker
- Font Pairing Tool
- XML Formatter
- XML Minifier
- WCAG Contrast Checker
ToolJiffy provides free developer tools for formatting, encoding and inspection in the browser. Many transformations process pasted data locally, while network lookup tools contact the destinations you request. Pages can also load resources, analytics and ads. Avoid pasting production secrets unless you have checked the specific tool and your organization’s policy.
Build and check a website before release
Copy HEX, RGB or HSL values from the CSS color picker and choose a heading and body pair with Google Fonts Pairing. Use the responsive screen tester to spot layout issues at preset widths on a site that permits embedding. Track install and offline checks with the PWA Checklist and review search copy with the meta description checker.
Format and validate data
Clean up unstructured API responses and validate data payloads instantly. Format and inspect nested API payloads using our JSON formatter and JSON validator (JSON Formatter). For markup files, clean and indent structures with our XML Formatter.
Test and debug
Debug code logic directly in your browser. Evaluate expression matches with real-time syntax highlighting using our regex tester online (Regex Tester). Validate mobile HTML markup with the AMP Validator, compare a curated browser support snapshot with the Browser Compatibility Checker, and standardize git commits using Semantic Commit Helper.
Encode, decode and generate
Format query parameters with URL Encode / Decode, inspect token structure using JWT Decoder, or generate IDs with UUID Generator. Local decoding is not a substitute for protecting production credentials; use test tokens whenever possible.
Convert between data formats
Convert tabular data in either direction with the JSON to CSV Converter (it has a CSV to JSON tab), and transform text logs with TXT to JSON Converter. Large inputs may slow down or exceed browser memory; check each tool’s output before importing it elsewhere.
Frequently Asked Questions
Is it safe to paste a real JWT or API response here?
Use test data where possible. Many formatters process input locally, but other developer tools make network requests and the site loads resources, analytics and ads. Check the exact tool before pasting a production secret.
Which regex flavors are supported?
Our Regex Tester uses standard JavaScript V8 regular expression rules (including lookbehinds, unicode flags, named capture groups, and global match flags).
Can I validate large JSON files?
Large JSON may work, but speed and maximum size depend on your device and browser memory.
Do the hash generators support SHA-256/512?
Yes. The Hash Generator calculates MD5 locally with JavaScript and SHA-1, SHA-256, SHA-384 and SHA-512 with Web Crypto when the browser provides a secure context. MD5 and SHA-1 are unsuitable for passwords or signatures.
Why client-side tools instead of regex101/jsonformatter sites?
Local transformation tools can avoid sending the entered data to a conversion server. Network lookup tools have different behavior; check the tool and avoid production secrets unless your policy permits them.
Do they work offline?
Not all tools work offline. Network lookups need connectivity, and some tool engines or site resources download on first use.