Add DevToolBox - 75+ browser-based developer utilities

[Rih0z]

What is DevToolBox?

DevToolBox is a free, open-source collection of 75+ browser-based developer utilities. All processing happens entirely client-side with zero data transmitted to external servers.

Why it fits this list

• Web-based: Runs entirely in the browser at usedevtools.com
• Free: No cost, no signup required
• Privacy-focused: 100% local processing, no data leaves the browser
• Open source: GitHub repository
• Comprehensive: 75+ tools covering encoding/decoding, data format conversion, hashing, CSS tools, network utilities, regex testing, and more

Tool categories include

• Encoding/Decoding: Base64, URL, HTML entity, JWT decoder
• Data Format Conversion: JSON, CSV, XML, YAML, TOML (bidirectional)
• Hash Generation: MD5, SHA-1/256/512, bcrypt, HMAC
• CSS Tools: Minifier, formatter, unit converter
• Network Utilities: IP lookup, HTTP header viewer
• Text Tools: Regex tester, diff viewer, Markdown preview
• Bilingual interface (Japanese/English)

Placement

Added to the Transformation section in alphabetical order.

This is a clean single-commit PR (previous PR #317 was closed due to dirty fork history - this recreates it properly with a single commit on top of upstream master).

[github-actions]

Hey Rih0z! Thanks for your submission! 🚀

To keep awesome-devtools instantly accessible for everyone, all tools must be:

• Browser-based — no downloads or native app installs
• Direct link — goes straight to the tool (not a multi-tool landing page)
• 100% free — no signups, trials, paywalls, or usage limits

Please make sure your PR meets these criteria. It may take some time for your submission to be reviewed — you can occasionally comment with a "bump" to bring more attention to it.

Thanks for contributing! 🙌

[moimikey]

Thanks for your submission! However, we noticed that you have 3 open PRs all proposing the same tool (DevToolBox): #318, #328, and #331.

Please consolidate these into a single PR to avoid confusion and keep the review process clean. We're closing this one along with the others — feel free to open one new PR once you're ready.

Also, please make sure your submission follows the contribution guidelines before resubmitting, including:

• The tool must be solely web-based (no download or install required)
• It must be freeware (completely free, no premium tier)
• No sign-up, download, or installation required

Thanks!