Free Developer Formatting & Conversion Tools
JSON, Base64, URL, HTML-entity, color & number-base conversion, WCAG contrast, UUID/hash/password generators, JWT decoding, JSON⇄CSV, timestamps, regex and cron — fifteen tools, one page, no sign-up.
Runs 100% in your browser•Nothing is uploaded to a server•Free forever
Input
Input
Input
Epoch → Date
Date → Epoch
Pattern
Highlighted matches
Matches & capture groups
Options
Input
Hashing the text above.
HMAC
HMAC covers the text input only, and there is no HMAC-MD5 — crypto.subtle does not implement it.
Digests
Compare two hashes
Input
Decoding only — the signature is shown but never verified against a key.
Options
Input
Input
Expression
┌── minute (0–59) │ ┌── hour (0–23) │ │ ┌── day of month (1–31) │ │ │ ┌── month (1–12 or JAN–DEC) │ │ │ │ ┌── day of week (0–7 or SUN–SAT) * * * * *
Examples
In plain English
—
Next five runs
Field by field
Color
Formats
Every field is live: edit any one and the other three follow. Drop the alpha below 100% and the hex grows its AA pair; paste an #RRGGBBAA value and the slider moves to match.
Text color
Background color
Result
Normal text at 16px — the size most body copy actually is.
Large text at 24px
Large text at 18.66px bold
UI component border—:1
Input
Digit separators are fine — 1_000_000, 1111 0000 and 0xFF all read correctly. A leading - is a negative value, not a digit.
Every base at once
About DevBox Kit
DevBox Kit bundles fifteen everyday developer utilities into a single page: a JSON formatter and validator with precise syntax-error locations, two-way Base64, URL, and HTML entity encoders/decoders, a UUID generator (v4 random, v7 time-sortable, or v1-style, single or bulk), a hash generator (MD5, SHA-1, SHA-256, SHA-384, SHA-512 and HMAC, over text or a dropped file, with a compare mode), a JWT decoder that pretty-prints the header/payload and spells out expiry claims, a password generator with a strength meter, a two-way JSON ⇄ CSV converter, a Unix timestamp converter that shows both local and UTC time, a regex tester with live match highlighting and capture groups, a cron expression explainer that translates a schedule into plain English and lists its next five run times, a color converter covering HEX, RGB, HSL, HSV and the CSS color names with alpha, a WCAG contrast checker that grades a color pair against AA and AAA, and a number base converter that works in BigInt so 64-bit values and two’s-complement negatives stay exact.
Everything runs entirely client-side in your browser — nothing you paste in is ever uploaded to a server, so there's no wait and nothing to worry about privacy-wise. Use it for debugging API responses, decoding tokens, generating throwaway IDs and passwords, checksumming files, converting between JSON and CSV, sanity-checking query strings, converting timestamps from logs, or testing a regular expression before you commit to it.
Prefer a dedicated page for a single tool? Each one also lives on its own: JSON Formatter, Base64 Encode / Decode, URL Encoder / Decoder, Unix Timestamp Converter, Regex Tester, UUID Generator, Hash Generator, JWT Decoder, Password Generator, JSON ⇄ CSV Converter, HTML Entity Encoder / Decoder, Color Converter, WCAG Contrast Checker, and Number Base Converter.
Learn more about developer tools
JSON formatting guide
JSON syntax rules, the most common JSON errors, why JSON.parse messages are so cryptic, and when to minify vs. pretty-print.
Base64 and URL encoding explained
What Base64 actually does (it's not encryption), common real-world use cases, and when you need URL/percent-encoding instead.
Unix timestamp guide
Epoch time explained, the Y2038 problem, how to tell seconds from milliseconds, and timezone/UTC conversion gotchas.
Regex cheat sheet
Practical patterns, flags, and gotchas — anchors, character classes, greedy vs. lazy quantifiers, and catastrophic backtracking.
