Every developer has a toolkit — a set of utilities they reach for daily. The best tools are the ones that work instantly in your browser, require no account, and just get the job done. Here are 25 free online tools that belong in every developer's bookmarks.
Data Format Tools
1. JSON Formatter & Validator
Paste malformed JSON, get it beautifully formatted with syntax highlighting and error detection. Essential for debugging API responses and config files.
2. JSON to CSV Converter
Converting API responses to spreadsheet-friendly formats is a daily task. Tools like DevKit's JSON to CSV converter make this instant.
3. YAML to JSON Converter
Docker Compose, CI configs, Kubernetes manifests — YAML is everywhere. A reliable YAML/JSON converter saves time when switching between formats.
4. XML to JSON Converter
Legacy APIs and SOAP services still use XML. Converting XML responses to JSON for modern frontends is a common need.
5. CSV Viewer & Editor
Preview CSV files without opening Excel. Good viewers handle large files, detect delimiters automatically, and let you sort/filter.
Encoding & Security Tools
6. Base64 Encoder/Decoder
Data URIs, API tokens, email attachments — Base64 encoding is everywhere. A fast encoder/decoder is essential.
7. URL Encoder/Decoder
Debugging query parameters with special characters? URL encoding issues are among the most common API bugs.
8. JWT Decoder
Decode JWT tokens to inspect headers, payloads, and expiration times without any external library.
9. Hash Generator (MD5/SHA)
Generate checksums for file integrity verification, password hashing comparisons, and data deduplication.
10. Password Generator
Generate secure, random passwords with configurable length, character sets, and entropy indicators.
CSS & Design Tools
11. CSS Gradient Generator
Visual gradient editors save hours of tweaking CSS. The best ones generate complex multi-stop gradients.
12. Box Shadow Generator
Layered shadows create depth. Interactive generators let you preview and copy production-ready CSS.
13. Flexbox Playground
Understanding flex properties visually is 10x faster than reading docs. Interactive playgrounds show results in real time.
14. CSS Grid Generator
Grid layouts are powerful but the syntax is complex. Visual generators help you prototype layouts quickly.
15. Color Palette Generator
Generate harmonious color schemes from a base color. Essential for design systems and brand consistency.
Code Transformation Tools
16. JSON to TypeScript
Paste a JSON response, get TypeScript interfaces. The DevKit converter handles nested objects and arrays intelligently.
17. Regex Tester
Test and debug regular expressions with real-time matching, group highlighting, and explanation of pattern components.
18. JavaScript/CSS Minifier
Quick minification for one-off scripts or inline styles. Useful when build tools feel like overkill.
19. SQL Formatter
Transform single-line SQL queries into readable, indented format. Makes complex joins and subqueries comprehensible.
20. Markdown Preview
Write and preview Markdown in real time. Useful for README files, documentation, and blog posts.
Utility Tools
21. Cron Expression Parser
Cron syntax reads like hieroglyphics. A parser that shows the next execution times in plain English is invaluable.
22. Timestamp Converter
Convert between Unix timestamps, ISO 8601, and human-readable dates. Debug time zone issues instantly.
23. UUID/ULID Generator
Generate unique identifiers for database records, API keys, and session tokens.
24. HTTP Status Code Reference
Quick lookup for all HTTP status codes with descriptions and common use cases. Faster than searching the RFC.
25. Placeholder Image Generator
Generate placeholder images of any size for mockups and prototypes without external services.
Where to Find These
All of these tools (and many more) are available for free at DevKit (tools.elunari.uk). No login, no tracking, no installs — just paste and go.