Developer utilities
Passwords, hashes, UUIDs, Base64/URL, JWT, JSON, cron, and more — free, in-browser.
Convert text to and from Base64, instantly in your browser.
Cron expression builderTranslate a cron schedule into plain English and see the next run times.
Hash generatorGenerate MD5, SHA-1, and SHA-256 checksums, in your browser.
IP address converterConvert IPv4/IPv6 between dotted, decimal, hex, and binary.
JSON formatter & validatorBeautify, minify, and validate JSON, in your browser.
JWT decoderDecode a JSON Web Token's header and payload, in your browser.
MAC address lookupIdentify the hardware vendor behind a MAC address from its OUI.
Password generatorBuild strong random passwords and test strength, in your browser.
Regex testerTest regular expressions against sample text with live matches.
Timestamp converterConvert between Unix time and human-readable dates.
URL encode/decodeConvert text to and from percent-encoding, in your browser.
User-agent parserBreak a user-agent string into browser, OS, and device.
UUID generatorGenerate random version 4 UUIDs, one or many, in your browser.
Everyday development throws up a hundred small conversions and checks — encoding a string, decoding a token, formatting messy JSON, or working out a cron schedule. These free developer utilities handle those tasks instantly in your browser, with nothing to install and nothing uploaded. They are quick, private, and always free — and if you build a cron schedule here, SJ Monitor's cron and heartbeat monitoring can alert you whenever a scheduled job fails to run.
Frequently asked questions
Are these tools really free with no limits?
Yes. The developer utilities run in your browser, require no account, and have no usage caps.
Is my data safe?
These utilities process input locally in your browser and do not upload it, so even sensitive strings stay on your device.
Is Base64 or a JWT payload safe to use for secrets?
No. Base64 is just reversible encoding, and a JWT payload is only encoded, not encrypted — anyone can read both. Never store sensitive data in either; use real encryption or keep secrets server-side.
Which hashing tool should I use for passwords?
None of these — MD5 and SHA are far too fast to safely store passwords. Use a slow, salted algorithm like bcrypt, scrypt, or Argon2 in your application code; the hash tool here is for checksums and integrity checks.
Can SJ Monitor tell me if a scheduled job fails?
Yes. Build the schedule with the cron tool, then point cron and heartbeat monitoring at the job — it expects a check-in for each run and alerts you when one is missed.
Other tool categories
Want any of this watched around the clock? Turn on SJ Monitor's cron & heartbeat monitoring — create a free account and we'll alert you the moment something changes.