Developer Utilities
The fast, offline, no-sign-up utilities you reach for daily — decode a JWT, plan a subnet, convert an epoch, generate an ID. Everything runs in your browser; nothing is sent anywhere.
Handbooks 1
Interactive Tools 13
JWT Decoder
A client-side JWT decoder. Paste a JSON Web Token and instantly see the decoded header and payload, with the standard claims (iss, sub, aud, exp, iat, nbf) explained and the expiry shown as a live countdown. Everything runs in your browser — the token is never sent anywhere, so it is safe to paste a real one.
CIDR Calculator
An IPv4 subnet calculator. Enter a CIDR block like 10.0.0.0/24 and instantly see the network address, broadcast address, usable host range, total and usable host counts, the subnet mask and wildcard mask, and the binary breakdown. Handy for planning VPC subnets, firewall rules and route tables — all computed in your browser.
Unix Time Converter
A Unix timestamp converter. Paste an epoch value (seconds or milliseconds — auto-detected) to get the human-readable date in both UTC and your local timezone, or pick a date to get the timestamp back. Shows the ISO 8601 string, relative time, and the current epoch ticking live. Runs entirely in your browser.
UUID & ULID Generator
A UUID and ULID generator. Produce cryptographically-random version-4 UUIDs or sortable ULIDs, one at a time or in bulk, with one-click copy. Explains when to reach for a random UUID versus a time-sortable ULID, and shows the structure of each. Uses the browser’s secure crypto — nothing is generated on or sent to a server.
Regex Tester
An interactive regular-expression tester. Type a pattern and flags, paste your test text, and see all matches highlighted with their positions, plus every numbered and named capture group. Explains the flags and common tokens, and runs entirely in your browser so nothing is sent anywhere.
Base64 & URL Encoder
A Base64 and URL encoding tool. Paste text to get its standard Base64, URL-safe Base64URL, and percent-encoded forms at once, or switch to decode to recover the original — all UTF-8 aware and computed in your browser. Handy for JWTs, data URIs, query strings and API debugging.
Chmod Calculator
A Unix file-permission calculator. Toggle read, write and execute for owner, group and others to get the octal mode (like 755) and the symbolic string (rwxr-xr-x), or type an octal number to see exactly which permissions it grants. Explains what each bit means and the common modes to reach for.
Password Entropy Calculator
A password strength calculator based on entropy. Type a password (analyzed only in your browser) to see the character pool it draws from, its entropy in bits, a strength rating, and an estimated time to crack at realistic offline attack speeds. Explains why length beats complexity and where the entropy model’s limits are.
Cron Expression Builder
A cron expression builder and decoder. Type a five-field cron schedule and instantly get a plain-English description plus the next several times it would fire, or start from a common preset. Supports ranges, lists and step values, and explains what each of the five fields means — all computed in your browser.
SQL Formatter
A lightweight SQL formatter. Paste a cramped, one-line query and get it back with each major clause on its own line, keywords cased consistently, and conditions indented — so you can actually read and review it. Runs in your browser; it formats for readability rather than parsing the full SQL grammar.
Markdown Table Generator
A Markdown table generator. Paste comma- or tab-separated data and get a properly aligned Markdown table you can drop into a README, a pull request, or docs — with a live rendered preview and a choice of column alignment. Everything runs in your browser.
Diff Checker
A text diff checker. Paste an original and a changed version to see a line-by-line comparison — additions, removals and unchanged lines highlighted — computed with a longest-common-subsequence diff, entirely in your browser. Handy for comparing configs, logs, JSON, or any two versions of text.
JSON Formatter & Diff
A JSON formatter, validator and diff tool. Paste JSON to validate it and pretty-print it, with clear error messages on invalid input. Paste a second document to see a key-sorted, value-level diff — so real changes stand out instead of formatting or key-order noise. Everything runs in your browser.
10.0.0.0/24 is pure bitwise arithmetic — network address, broadcast, usable host range, all derivable on the spot. A Unix timestamp is seconds (or milliseconds) since 1970-01-01 UTC, and converting it is just date math. A UUID v4 or ULID is a few random bits in a fixed layout. Because all of it is local computation, the right place to do it is the one where the data never leaves your machine: every tool in this hub runs entirely in your browser, offline-capable, with nothing logged or transmitted — which is exactly what you want when the input is a real token, a real address plan, or production data.