Developer Utilities

Small developer utilities that save a trip to a random website. Encode and decode Base64, explain a regex, build UTM links, generate QR codes and vCards, and more — the everyday helpers. Free in your browser, and available by API when you need them in a script.

SEDOL check digit
For the body B0YBKJ the check digit is 7, so the full SEDOL is B0YBKJ7. The tool computes that digit for any six-character body or validates a complete code…
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Shell argument quoter
hello world becomes 'hello world', a single safe shell argument: spaces, quotes, asterisks and other special signs are wrapped in single quotes so the shell…
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Monoalphabetic substitution cipher
With the key QWERTYUIOPASDFGHJKLZXCVBNM, Hello World becomes Itssg Vgksr: you supply the whole 26-letter cipher alphabet, every letter keeps one fixed…
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Canadian SIN check digit
The base 04645428 gets check digit 6, giving the full SIN 046454286. Enter eight digits to compute the Luhn digit or nine to validate a complete Social…
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French SIREN Luhn check
The body 732 829 32 gets check digit 0, giving SIREN 732 829 320, while a mistyped 732 829 321 fails.
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French SIRET Luhn check
73282932000074 passes: the Luhn check over all fourteen digits holds, and its first nine digits, the SIREN 732829320, pass their own check too, leaving 00074 as…
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Soundex encoder
Robert and Rupert both become R163: the first letter stays, the next consonant sounds turn into three digits, and short codes are padded with zeros, so names…
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Spanish spelling alphabet
SOS becomes Sábado Oviedo Sábado: every letter, Ñ included, and every digit gets its Spanish code word, from Antonio for A to Zaragoza for Z, so names and…
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SSCC-18 check digit calculator
The 17 data digits 00614141123456789 get check digit 0, so the full SSCC-18 is 006141411234567890.
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Germany tax ID check digit
Enter the first ten digits of a German Steuer-ID, such as 8609574271, and get its check digit, 9, plus the full number 86095742719.
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Unicode strikethrough text
Type Hello and get H̶e̶l̶l̶o̶: a long stroke mark is placed after each of its 5 letters, so the crossed-out look travels as plain text into chats, bios and…
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Unicode subscript text
Type H2O C6H12O6 x1 and get H₂O C₆H₁₂O₆ ₓ₁: digits, plus, minus, equals, brackets and the lowercase letters Unicode supports drop below the line, ready to paste…
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Unicode superscript text
Type x2 + y3 and get ˣ² ⁺ ʸ³: digits, plus, minus, equals, brackets and many Latin letters rise into Unicode superscripts that keep their raised look wherever…
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Swedish spelling alphabet
Type SOS and get Sigurd Olof Sigurd: every letter, including Å, Ä and Ö, becomes its Swedish code name and digits become Noll to Nio, ready to read aloud on a…
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System V sum checksum
The word hello gives checksum 532 and 1 block, exactly what sum -s prints on Unix. Paste text to reproduce the classic System V figure, not the BSD…
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T9 predictive text encoder
Type hello and get 43556, the keys you would press on a classic phone pad where 2 holds ABC and 9 holds WXYZ.
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Police ten-code translator
Type 10-4 and read Acknowledgement (OK / message received), or type a phrase such as message received to get the code back.
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Ubbi Dubbi translator
Hello world becomes Hubellubo wuborld: the syllable ub goes before every vowel a, e, i, o and u, while y, spaces and punctuation stay as they are.
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UIC wagon number check digit
A wagon whose first eleven digits are 21812471217 gets check digit 3, so its full UIC number reads 218124712173.
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Unicode escape sequence converter
Type Hi and get \u0048\u0069; an accented é becomes \u00e9 and the emoji U+1F600 becomes the pair \ud83d\ude00.
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Unicode NFD normalizer
The word café, written with one é, comes out as five code points: c, a, f, e and a combining acute accent.
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Unicode NFKC normalizer
file ㎞ ① becomes file km 1: ligatures, fullwidth letters, circled digits and other styled variants fold into plain text, and accents are then recomposed, so…
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Unicode NFKD normalizer
file ① café becomes file 1 café with the accent split off: ligatures expand into separate letters, circled digits become plain numbers and accented letters break…
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UPC-A check digit
The product number 01234567890 gets check digit 5, so the full UPC-A reads 012345678905. Paste a complete twelve-digit code from a partner file or scanner to…
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UPC-E converter
The UPC-E code 425261 expands to the UPC-A 042100005264: the zeros squeezed out for small packages are put back, manufacturer 42100 and product 00526, and the…
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Upside down text flip
Hello World! comes out as ¡plɹoM ollǝH: each letter is swapped for a rotated Unicode look-alike and the order is reversed, so it reads right when the screen is…
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RFC 3986 percent encoder & decoder
Under strict RFC 3986, hello world!'()* becomes hello%20world%21%27%28%29%2A: only letters, digits, hyphen, period, underscore and tilde stay as they are.
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UTF-32 code unit encoder
Turn text into fixed-width UTF-32 values: “Hi” becomes 00000048 00000069, two units and 8 bytes, and an emoji like U+1F600 stays a single unit, 0001F600.
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UTF-7 encoder and decoder
Encode text as UTF-7 so it survives seven-bit ASCII channels: café becomes caf+AOk-, and decoding brings back the original word.
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Modified UTF-7 IMAP encoder
Get the exact folder name an IMAP server expects: Inbox/日本語 becomes Inbox/&ZeVnLIqe-, and a cryptic token from a protocol log decodes back into its readable…
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UK UTR check digit
Compute or check the leading digit of a UK Unique Taxpayer Reference: the body 123456789 gives check digit 1, so the full UTR is 1123456789.
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Uuencode encoder & decoder
Turns “Hello, world!” into a classic uuencode document headed begin 644 data.txt, and reads such documents back into text.
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VIC cipher
Encrypts ATTACK AT DAWN with the board key COMPUTERS, null digits 37 and the keys ORANGE and BLUE into 61363 17174 31939 70373 3916, and decrypts it back.
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Western Union phonetic alphabet
Spells SOS as Sugar Ocean Sugar using the classic Western Union telegraph table, from Adams for A to Zero for Z, and turns a string of code words back into…
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XML entity encoder
Escapes the five characters XML reserves, so “Tom & Jerry <3” becomes “Tom &amp; Jerry &lt;3”, and turns &amp;, &lt;, &gt;, &apos; and &quot; back into plain…
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xxencode encoder
Packs “Hello, world!” into a classic xxencode block, begin 644 hello.txt and all, using only plus, minus, digits and letters so no EBCDIC gateway can mangle it…
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yEnc encoder and decoder
Encodes “Hello Usenet” into a framed yEnc fragment, with a =ybegin header and a =yend line carrying the checksum 38A1E859, and decodes such fragments back to…
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Zero-width character encoder
Hides a secret inside ordinary text with invisible Unicode characters: “Hi” tucked into “Hello world” becomes 18 zero-width characters nobody sees, and decoding…
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Minify CSS code and measure the size reduction
Shrink a stylesheet without touching its meaning: the sample drops from 101 to 71 bytes, a 29.7 % saving, while the text inside quotes, even a /* label */ {x}…
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Compute an exponential backoff schedule for retries
See exactly how long each retry waits: a base of 250 with multiplier 2 and a cap of 2000 gives 250, 500, 1000, 2000, 2000 and 2000 over 6 retries, with no…
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A1Z26 cipher
Swap each letter for its place in the alphabet: HELLO becomes 8 5 12 12 15, and a list of numbers from 1 to 26 turns back into letters.
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RFC 1924 Base85 encoder & decoder
“Hello World” becomes 7KPt{PR^XAyM<W in RFC 1924 Base85, the 85-character alphabet first proposed to write a 128-bit IPv6 address in twenty characters, here…
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Ternary / base-3 converter
42 is 1120 in ternary: one 27, one 9, two 3s and no units, shown step by step so you can check the arithmetic.
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Factorial number system converter
Convert whole numbers to factoradic and back: 23 is 3:2:1:0, also written 3210!, because three times 3! plus two times 2! plus one times 1! adds up to 23.
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Portugal NIF check digit calculator and validator
The eight digits 50196484 get the check digit 3, which completes the NIF as 501964843. Enter eight digits to calculate the ninth, or all nine to see whether the…
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Build a Content-Security-Policy header from allowed sources
Four rows, from default-src with 'self' to upgrade-insecure-requests on its own, become one policy line joined by semicolons, in your order.
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Convert Unix permissions between symbolic and octal
rwxr-xr-- converts to 754, and 754 converts back to rwxr-xr--, because read counts 4, write 2 and execute 1 for each audience.
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Seeded memorable passphrase generator
With 6 words and a hyphen, the same private seed always returns parade-orange-globe-marsh-birch-earth, so the phrase can be rebuilt instead of stored.
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Lookup an ASCII Character Code in Decimal, Hex, Octal, and Binary
The letter A is decimal 65, hexadecimal 0x41, octal 0o101 and binary 01000001. Type one character, a decimal code or a 0x code and get the full table entry…
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Convert number between bases 2–36 with digit validation
The hexadecimal number -deadBEEF becomes -1PS9WXB in base 36. Enter a whole number, say which base it is written in and pick any target base from 2 to 36; long…
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CSS Beautifier
A one-line stylesheet comes back as indented blocks with each declaration on its own line, yet a semicolon inside a quoted font name like “A; B” stays where it…
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HTML Beautifier
A whole page squeezed onto one line comes back with every nested element on its own line, two spaces deeper than its parent, so you can pair opening and closing…
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JavaScript Beautifier
A function squeezed onto one line comes back as indented blocks, while the semicolons in a for-loop header stay together and a string such as “a;b” is left…
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Format a Keep a Changelog entry from grouped changes
Give it version 2.4.0, the date 2026-07-25 and your lists of changes, and it returns the entry headed ## [2.4.0] - 2026-07-25 with Added, Changed, Fixed and…
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Parse command-line arguments with a flag and option spec
List the switches and options your program accepts, and it sorts the command line for you: --tag=stable --tag latest becomes the two tags stable and latest…
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Conventional Commits message linter and parser
Check a commit header before it lands: feat(parser)!: support escaped delimiters is read as type feat, scope parser and a breaking change, while an unknown type…
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Count lines of code by type
See how much of a file is real code: the sample function gives 6 lines, of which 4 are code, 1 is a comment and 1 is blank, judged by the comment rules of the…
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Compute a code file line diff
See exactly what changed between two versions of a file: rewriting return a + b as two new lines shows 2 added, 1 removed and 3 unchanged, with old and new line…
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Parse a Docker Image Reference into Registry, Repository, Tag, or Digest
Paste registry.example.com:5000/team/service:2026.07 and get registry registry.example.com:5000, repository team/service and tag 2026.07, because the port colon…
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Dockerfile best practices linter with line numbers
Three checks before your image is built: in the sample, node:latest on line 1, a missing WORKDIR and the RUN on line 5 that follows the one on line 3 give 3…
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