This is the grab-bag category: the utilities that belong to no framework and no platform, but turn up in the middle of a debugging session. Subnet arithmetic, timestamp conversion, identifier generation — small jobs that are tedious by hand and not worth installing anything for.

Every utility in this category runs entirely in your browser. Nothing is uploaded, nothing is stored and there is no sign-up. Once a page has loaded it keeps working even if your connection drops.

🧰 Free DevToolBox Tools

Client-side and free — nothing you paste leaves your browser:

CIDR / Subnet Calculator — IPv4 and IPv6 subnet maths: network, broadcast, mask and usable range.
Timestamp Converter — Convert Unix seconds or milliseconds to a readable date, in any timezone.
UUID Generator — Generate v1, v4 and v7 identifiers individually or in bulk.
JSON Formatter — Format, validate and tree-view JSON with clear error positions.
SQL Formatter Online — Beautify SQL across 15+ dialects, or minify it for production.
Regex Tester Online — Test a regular expression with live highlighting, match groups and a pattern explainer.
JWT Debugger — Decode and verify JWT tokens without sending them anywhere.
Diff Checker — Compare text, code or JSON side by side.
Base64 Encoder — Encode text and files to Base64, URL-safe included.
Base64 Decoder — Decode Base64 strings and files back to readable text.
URL Encoder/Decoder — Encode and decode URL-unsafe characters per RFC 3986.
HTML Entity Encoder — Convert special characters to HTML entities and back.
Hash Generator — MD5, SHA-1/256/512, CRC32 and HMAC digests in one page.

❓ Frequently Asked Questions

Are these tools really free?

Yes — all of them, with no usage limit and no sign-up. The site is a static deployment and every tool is a self-contained page.

Does anything get uploaded to a server?

No. Each tool is plain JavaScript running in the page. You can confirm it in your browser's network tab: after the page loads there are no outbound requests.

Can I use these tools offline?

Once a page has loaded you can keep working if the connection drops, because nothing else is fetched. Reloading naturally requires a connection.

Which tool should I reach for first when debugging?

Start with the Diff Checker to see what changed, then the JSON or SQL formatter to make the data readable, and the encoding tools when a value arrives in a form you do not recognise.