Book Cipher Decoder

Paste the numbers into Code to decode and the pages both sides own into Your key text.

Book Cipher Decoder

Code to decode: 1.3.4 2.4.2 1.6.4 2.3.8 2.4.8 1.1.7

This is a sample. Type or paste your own code over it.

Message

the key is under the owl
Not sure of the format? Try every format

The same code read in every format against the same key text. The one that finds every reference and reads as words is the format it was written in.

FormatReadingFoundUse it
Page, line and word (page.line.word) Likelythe key is under the owl6 of 6In use
Page, line and word, first letter (page.line.word) Likelytkiuto6 of 6
Page, line and letter (page.line.letter) Likelyohraor6 of 6
Word number (word)visitors asked to are to are visitors the to are…18 of 18
Word number, first letter (word)vatatavttaaaatavvo18 of 18
Letter number (letter)vsiiiivoiissiisvvr18 of 18
Line and word (line.word)[?] [?] [?] [?] [?] [?]0 of 6
Line and word, first letter (line.word)[?][?][?][?][?][?]0 of 6
Line and letter (line.letter)[?][?][?][?][?][?]0 of 6
Word and letter (word.letter)[?][?][?][?][?][?]0 of 6
Paragraph and word (paragraph.word)[?] [?] [?] [?] [?] [?]0 of 6
Page and word (page.word)[?] [?] [?] [?] [?] [?]0 of 6
Line, word and letter (line.word.letter)eo[?][?][?]r3 of 6
Chapter, verse and word (chapter.verse.word)[?] [?] [?] [?] [?] [?]0 of 6
Page, line, word and letter (page.line.word.letter)[?][?][?][?][?][?]0 of 6
More options

Counting switches and a different edition

  • All 6 references found.
  • Key text: 2 pages, 16 lines, 149 words, 606 letters.
The working, step by step (6 rows)

Each reference, read as page, line, word.

ReferenceWhere it pointsGives
1.3.4page 1, line 3, word 4the
2.4.2page 2, line 4, word 2key
1.6.4page 1, line 6, word 4is
2.3.8page 2, line 3, word 8under
2.4.8page 2, line 4, word 8the
1.1.7page 1, line 1, word 7owl

Next step All letters, no numbers? Shift them against a keyDecoded letters still scrambled? Unshuffle them

How it works

This book cipher decoder looks up each number in a text you paste, in any of 15 formats from a plain word count to page, line and word. No book is bundled: yours must match the sender's word for word.

Read the full guide

Paste the numbers, then the key

Your key text holds 200,000 characters. Pick a Reference format, or open Try every format and press Use on the row that reads. For page formats, type a line reading [page] wherever the book turns a page. The working, step by step explains every miss, such as page 1, line 2 has 8 words, so there is no word 40.

When the decode is nearly right

Real words in nonsense order mean the format is right and the counting off. Somebody counted a heading you did not. Under Counting switches and a different edition, shift a count by one or tick Count a hyphenated word as two. The second Beale paper is said to fit only a Declaration of Independence that counts self-evident as two words.

Tips
  • Numbers like 120.9.7 are usually Page, line and word. Benedict Arnold and John André wrote theirs so: 120.9.7 was general.
  • Single numbers, unrelated words? Try Word number, first letter. Beale's second paper opens 115: the 115th word, instituted, gives I.
  • Under Encode, Pick new positions picks another place for each word. A repeated word need not repeat its number.

Questions and answers

Can I decode a book cipher without the book?

Not here: the page looks numbers up in a text, so it needs the text. With a shortlist, paste a chapter of each book and look in Try every format for a sentence. Keep real secrets elsewhere: Wikipedia's article calls the cipher quite easily broken.

What if my code has letters mixed in with the numbers?

Leave them in. Letters stuck to a reference join the decoded word. Arnold handled endings his book lacked that way, writing 94.9.9ing and 207.8.17ed. A letter between the numbers suggests a dictionary code with lettered columns, which pasted text cannot supply.

Which text makes a good key for my own puzzle?

One whose wording and line breaks never change: a poem, or a text with numbered verses. Chapter, verse and word survives a new edition of the same translation. If it lacks a word, spell it with a first-letter format. E-books reflow, so page numbers fail.

More tools

Browse Text styles

All 15 reference formats

One number for each word or letter 3

  • Letter number One number for each letter: count letters from the start of the key text, skipping spaces, digits and punctuation. The numbers run as high as the key has letters, so this format suits a short key such as a single verse or a paragraph.
  • Word number One number for each word of the message: count words from the start of the key text and take the whole word. Wikipedia's article on the book cipher calls this the simple version, and notes that it fails if the message uses a word that does not appear in the text.
  • Word number, first letter One number for each letter of the message: find that word and keep only its first letter. The second Beale paper is written this way against a printing of the United States Declaration of Independence, where number 115 lands on the word instituted and gives the letter I.
Show all 15 reference formats (12 more)

Two numbers 6

  • Line and letter Two numbers: the line, then the letter on that line, counted across its words with spaces and punctuation skipped. A second number larger than the line has words is the quickest way to tell it from Line and word.
  • Line and word Two numbers: the line, counted through the whole text, then the word on that line. It needs a key whose line breaks never move, such as a poem or a printed notice. Blank lines are not counted.
  • Line and word, first letter Two numbers that find a word by line and position, of which only the first letter is kept. It spells names and words the key text does not contain, at the price of one reference for each letter.
  • Page and word Two numbers: the page, then the word counted from the top of that page. The key text needs a [page] marker line wherever the printed book turns a page.
  • Paragraph and word Two numbers: the paragraph, then the word inside it, counted across the paragraph's lines. A blank line or a page marker ends a paragraph. It survives a text being reflowed, because paragraphs stay put when line breaks move.
  • Word and letter Two numbers: the word, counted from the start of the text, then the letter inside that word. The second number stays small, because few words run past ten letters.

Three numbers 5

  • Chapter, verse and word Three numbers for a key text with numbered verses: chapter, verse, then the word inside the verse. Verse numbers are printed in the text itself, so this is the one three-number format that survives a change of edition, as long as the translation is the same.
  • Line, word and letter Three numbers with no page: the line counted through the whole text, the word on that line, the letter inside that word. It fits a key that is one poem or one page long.
  • Page, line and letter Three numbers: the page, the line on that page, then the letter on that line with spaces and punctuation skipped. When the third number is larger than the number of words on the line, this is the format to try.
  • Page, line and word Three numbers: the page, the line on that page, the word on that line. Benedict Arnold and John André wrote theirs with full stops between the numbers, and Wikipedia's article on the Arnold Cipher decodes 120.9.7 as the word general.
  • Page, line and word, first letter Three numbers that find a word by page, line and position, of which only the first letter is kept. Use it when the book is fixed but the message needs words the book never uses.

Four numbers 1

  • Page, line, word and letter Four numbers: page, line, word, then the letter inside that word. It is the most exact format and the slowest to write, since every letter of the message costs four numbers.

How this list was compiled: The 15 formats are the ways a number in a book cipher can point into a text: by word, line, paragraph, page, verse or letter. The list was compiled for this site from the schemes described in Wikipedia's articles Book cipher (https://en.wikipedia.org/wiki/Book_cipher), Arnold Cipher (https://en.wikipedia.org/wiki/Arnold_Cipher) and Beale ciphers (https://en.wikipedia.org/wiki/Beale_ciphers), all read on 2026-09-19, plus the letter-level variants that follow from them. Historical notes in the list are stated as those articles record them. Both sample key texts were written for this site and are not quotations from any book. Every example code was produced by a script that encodes the message against the sample, decodes it again with a separate routine and checks that the two agree, using the counting rules this page describes: blank lines are skipped, a [page] line starts a page, punctuation is stripped from the ends of a word, and a hyphenated word is one word. Licence: own work