Ciphers, scripts and codes, each table generated from its rule

Cipher decoder

Paste a coded message and see every reading it could have, most likely first: Caesar shifts, ROT13, Atbash, A1Z26, binary, ASCII, braille, roman numerals. Then open the cipher's own page to work on it. Nothing you paste leaves your browser.

26 readings, most language-like first. On a short text the order is a guess.

  1. Caesar shift shift 11 THE KEY IS UNDER THE BLUE FLOWERPOT BY THE BACK GATE Open the tool
  2. Caesar shift shift 4 AOL RLF PZ BUKLY AOL ISBL MSVDLYWVA IF AOL IHJR NHAL Open the tool
  3. Caesar shift shift 1 DRO UOI SC EXNOB DRO LVEO PVYGOBZYD LI DRO LKMU QKDO Open the tool
  4. Caesar shift shift 24 GUR XRL VF HAQRE GUR OYHR SYBJRECBG OL GUR ONPX TNGR Open the tool
  5. Caesar shift shift 17 NBY EYS CM OHXYL NBY VFOY ZFIQYLJIN VS NBY VUWE AUNY Open the tool
  6. Caesar shift shift 8 WKH NHB LV XQGHU WKH EOXH IORZHUSRW EB WKH EDFN JDWH Open the tool
  7. Caesar shift shift 23 HVS YSM WG IBRSF HVS PZIS TZCKSFDCH PM HVS POQY UOHS Open the tool
  8. Caesar shift shift 10 UIF LFZ JT VOEFS UIF CMVF GMPXFSQPU CZ UIF CBDL HBUF Open the tool
  9. Caesar shift shift 20 KYV BVP ZJ LEUVI KYV SCLV WCFNVIGFK SP KYV SRTB XRKV Open the tool
  10. Caesar shift shift 15 PDA GAU EO QJZAN PDA XHQA BHKSANLKP XU PDA XWYG CWPA Open the tool
  11. Caesar shift shift 9 VJG MGA KU WPFGT VJG DNWG HNQYGTRQV DA VJG DCEM ICVG Open the tool
  12. Caesar shift shift 12 SGD JDX HR TMCDQ SGD AKTD EKNVDQONS AX SGD AZBJ FZSD Open the tool
  13. Caesar shift shift 2 CQN TNH RB DWMNA CQN KUDN OUXFNAYXC KH CQN KJLT PJCN Open the tool
  14. Caesar shift shift 3 BPM SMG QA CVLMZ BPM JTCM NTWEMZXWB JG BPM JIKS OIBM Open the tool
  15. ROT13 RFC ICW GQ SLBCP RFC ZJSC DJMUCPNMR ZW RFC ZYAI EYRC Open the tool
  16. Caesar shift shift 7 XLI OIC MW YRHIV XLI FPYI JPSAIVTSX FC XLI FEGO KEXI Open the tool
  17. Caesar shift shift 22 IWT ZTN XH JCSTG IWT QAJT UADLTGEDI QN IWT QPRZ VPIT Open the tool
  18. Atbash VHK EKQ GW UBLKX VHK NDUK JDASKXZAV NQ VHK NOME IOVK Open the tool
  19. Caesar shift shift 19 LZW CWQ AK MFVWJ LZW TDMW XDGOWJHGL TQ LZW TSUC YSLW Open the tool
  20. Caesar shift shift 21 JXU AUO YI KDTUH JXU RBKU VBEMUHFEJ RO JXU RQSA WQJU Open the tool
  21. Caesar shift shift 14 QEB HBV FP RKABO QEB YIRB CILTBOMLQ YV QEB YXZH DXQB Open the tool
  22. Caesar shift shift 18 MAX DXR BL NGWXK MAX UENX YEHPXKIHM UR MAX UTVD ZTMX Open the tool
  23. Caesar shift shift 5 ZNK QKE OY ATJKX ZNK HRAK LRUCKXVUZ HE ZNK HGIQ MGZK Open the tool
  24. Caesar shift shift 6 YMJ PJD NX ZSIJW YMJ GQZJ KQTBJWUTY GD YMJ GFHP LFYJ Open the tool
  25. Caesar shift shift 25 FTQ WQK UE GZPQD FTQ NXGQ RXAIQDBAF NK FTQ NMOW SMFQ Open the tool
  26. Caesar shift shift 16 OCZ FZT DN PIYZM OCZ WGPZ AGJRZMKJO WT OCZ WVXF BVOZ Open the tool

How to use it

  1. Paste the coded text into the box. Every decoder the site has tries it at once: the 25 Caesar shifts, Atbash, A1Z26, binary, ASCII codes, braille and roman numerals.

  2. Read the list. Each reading is labelled with the cipher and, for a shift, the number, and the list is sorted with the one that most resembles English at the top.

  3. Open the tool beside a reading to work on it: change the shift, decode a longer message, or read how the cipher works and why it breaks.

What is on the site

The Caesar cipher is where almost every treasure hunt starts: each letter moves a fixed number of places along the alphabet. The message in the box above was shifted by eleven, and the decoder finds THE KEY IS UNDER THE BLUE FLOWERPOT BY THE BACK GATE without being told, by trying all 25 shifts and picking the one that reads like a language. The page has a free shift, ROT13 and the brute-force list.

The Vigenère cipher replaces the single shift with a keyword: each letter of the key decides the shift of one letter of the text. It was called unbreakable for three hundred years, and the page shows the whole tabula recta, generated row by row from the Caesar shift.

Atbash writes the alphabet backwards, so that secret becomesHVXIVG. It needs no key and is its own inverse, which makes it the first cipher to teach a child. A1Z26 writes each letter as its number in the alphabet, so hello becomes 8-5-12-12-15; it is the code of a thousand puzzle books.

The binary translator writes each byte as eight digits, so hi becomes01101000 01101001. It works in UTF-8, so accents and emoji survive the round trip. The ASCII table lists the 128 codes with decimal, hex, binary and the name of every control character.

The braille alphabet has a translator and the table of letters, numbers and signs; hi in braille is ⠓⠊, and the table is derived from Louis Braille's decades, which the page explains. Roman numerals convert both ways with the thirteen values that generate every numeral to 3999.

Three scripts have reference hubs with a section per sign and a trainer: the Greek alphabet, the Egyptian uniliterals with a name translator, andcuneiform with a syllable translator. Each says on the page what its table is and what it is not.

Where the tables come from

Every table here is the output of a program that implements the rule of its cipher, and the numbers and codes on the pages are that program's output too, not text an author typed: braille from the dot lists of the first ten letters, roman numerals from thirteen values, the Caesar table from the shift itself. Where a table cannot be derived, because the knowledge is external, it is authored and checked against a source: the 33 ASCII control names against the Unicode character database, the signs of the Greek, Egyptian and cuneiform tables against the code points the same database gives their names. Theabout page sets out how that is kept honest.

The same care goes into what a decoder cannot do. A code over 26 letters, such as A1Z26, has no room for a question mark; instead of losing it silently, the box names the characters it left out. And the decoder above is a list, never a verdict: on a short text the frequency score can prefer the wrong shift, so the candidates stay on screen with their labels.

For classrooms and treasure hunts

The substitution ciphers page gathers the ciphers that turn up in scavenger hunts, camps and maths lessons, from the easiest to the hardest. Each comes with a puzzle already encoded, the answer hidden behind a click, and a link to its decoder. The puzzles were encoded by the same programs that decode them, so a puzzle and its answer cannot disagree.

None of the tools asks for an account, stores what you typed, or sends text to a server. The work happens inside the page, on your device, and keeps working if the connection drops after the page has loaded.

Frequently asked

How does the decoder know which cipher was used?

It does not know; it tries. Every keyless cipher on the site decodes the text, and each result is scored by how closely its letter frequencies match English. A real sentence has many E, T and A; a wrong decoding is a flat spread. The list is sorted by that score, and on a short text the top result can be wrong, so the ranked list stays visible.

Which ciphers can it identify?

The ones that need no key: the Caesar cipher at any of its 25 shifts, including ROT13, Atbash, A1Z26, binary, ASCII codes, braille and roman numerals. A Vigenère cipher needs its key, and no honest decoder can guess one from a short text, so that page has its own tool with a key field.

What is a substitution cipher?

Any code in which each letter of the message is replaced by another symbol under a fixed rule. In the Caesar cipher the rule is a shift along the alphabet; in Atbash it is the alphabet reversed; in binary each letter becomes eight digits. The rule is the key, and whoever has the rule can read the message.

Are the tables here correct?

Each table is produced by a program that implements the rule of the cipher and is tested against it. The braille table, for instance, is derived from the first ten signs and the logic of the decades; roman numerals from thirteen values and the subtractive rule; ASCII control names are checked against the Unicode character database.

Does anything I paste get sent anywhere?

No. Every decoder runs in your browser. Nothing you paste leaves your device, there is no account, and there is no tracking script on the page.