Tools
Self-contained utilities. Each one is a single page that keeps working offline once loaded, and nothing you type leaves the browser.
Networking
Subnet Calculator
Work out network address, broadcast, usable host range and mask from any IPv4 address and prefix length.
MAC Address Formatter
Reformat a MAC address between colon, hyphen and Cisco dot notation, and read the bits that tell you what kind of address it is.
Port Reference
Filterable list of the TCP and UDP ports that actually come up in day-to-day work, searchable by number, service or protocol.
Encoding and data
Encoder and Decoder
Convert text to and from Base64, Base64url, URL percent-encoding and HTML entities, with correct handling of non-ASCII characters.
JWT Decoder
Read the header and claims of a JSON Web Token, with timestamps resolved to real dates and expiry checked against now.
JSON Formatter
Reindent, minify and validate JSON, with the parse error pointed at the line and column that broke it.
Hash Generator
Produce SHA-1, SHA-256, SHA-384 and SHA-512 digests of text or a file, computed locally by the browser's own crypto engine.
Storage
Sysadmin
Password Generator
Generate random strings or passphrases using the browser's cryptographic random source, with the real entropy shown for each.
Cron Explainer
Read a five-field cron expression back in plain English and see the next run times, so you can check a schedule before it goes live.
Epoch Converter
Convert Unix timestamps to readable dates and back, in both UTC and local time, with seconds and milliseconds handled automatically.