Developer Tools
Encode, decode, test and generate values for everyday development work. Input is processed in your browser.
Data Converter
Convert and validate data locally in your browser for common development tasks.
Base64 / URL / JWT
Encode and decode Base64 or URLs and inspect JWT headers and payloads in the browser.
Cron Parser
Read Unix, Spring, Quartz and AWS cron expressions, see the next run times in any time zone, or build an expression field by field.
RegEx Tester
Test regular expressions with highlighted matches and capture groups, preview replacements, and copy the pattern as code for six languages.
Hash Generator
Calculate MD5, SHA-1, SHA-256, SHA-384 and SHA-512 hashes or HMACs of text or files in your browser and compare them with an expected checksum.
Password & UUID Generator
Generate random passwords and UUIDs (v4 and v7) in your browser with the Web Crypto API, and inspect the version and timestamp of a UUID.
Unix Timestamp Converter
Convert Unix timestamps in seconds, milliseconds, microseconds or nanoseconds to dates in any time zone, and dates back to timestamps, in your browser.
Choosing the right developer tool
Start from the kind of value in front of you. Base64 / URL / JWT suits strings from an API response or an Authorization header: it encodes and decodes Base64 as UTF-8 text (decoding also accepts the URL-safe variant) and percent-encoding, and shows a token's header, payload and any iat, nbf and exp dates. URL decoding leaves plus signs as they are, and Base64 that decodes to binary data, such as an image, is reported as an error instead of being shown. JWT decoding does not verify the signature, so a decoded token is no proof of who issued it or that it is valid. Use the Cron Parser to check a Unix, Spring, Quartz or AWS EventBridge schedule and list its next run times in a time zone you choose, and the RegEx Tester when a pattern matches too much or too little.
The Hash Generator calculates MD5, SHA-1, SHA-256, SHA-384 and SHA-512 hashes of text or a file and compares them with an expected checksum, for example to check a download against a published SHA-256 value. It also calculates HMACs with the SHA algorithms. The Password & UUID Generator creates random passwords with an entropy estimate and v4 or v7 UUIDs, and can inspect an existing UUID. The Unix Timestamp Converter helps when a log shows a number such as 1700000000: unless you choose the unit yourself, it guesses from the size of the number whether it is in seconds, milliseconds, microseconds or nanoseconds, and it also turns dates into timestamps.
These tools run as JavaScript in your browser, and what you enter is not sent to LeedyBox. Passwords and the random parts of UUIDs come from the browser's cryptographic random number generator. SHA hashes and HMACs use the Web Crypto API, which browsers offer only in secure contexts such as HTTPS pages, while MD5 is calculated by the page's own script. A file is read into memory as a whole before it is hashed, so very large files can be slow or fail. Patterns are tested with the JavaScript regex engine and may behave differently in Python, Java or a database; matching normally runs in a background worker that is stopped if it takes longer than two seconds. Cron and timestamp results depend on your browser's time zone data.
The developer guides explain cron syntax, hash functions, password entropy and UUID versions, regular expressions and Unix time in more depth.