About Dev Kit

Dev Kit puts the small everyday utilities on one page: pretty-print and validate JSON, test a regular expression against sample text, translate a cron line into plain English, base64 and URL encode or decode, hash a string with MD5 or SHA, decode the payload of a JWT, and convert between Unix time and a date.

Everything runs in the page. After the first visit it works with the network off, and no input you paste is sent anywhere.

How to use it

  1. Open the tool and pick the utility from the list.
  2. Paste your input: JSON, a pattern, a token, a timestamp.
  3. Read the result. Errors point at the character or field that failed.
  4. Copy the output. Recent inputs stay until you close the tab.

Common questions

Is a pasted JWT or API response sent anywhere?

No. Decoding and hashing run in JavaScript in the tab. Nothing is logged or transmitted.

Does the JWT tool verify the signature?

It decodes and shows the header and payload and checks the expiry. It does not verify the signature, which needs the secret or public key.

Which hash algorithms are included?

MD5, SHA-1, SHA-256, and SHA-512 for text input.

Does it really work offline?

Yes. A service worker caches the page on the first load, so it opens with no connection after that.