Caesar Cipher Encoder / Decoder

Shift letters by any amount to encode or decode a Caesar cipher.

Shift: 3

Input

Encoded

Cipher solver — all 26 possible decodings

↓0The quick brown fox jumps over the lazy dog.

↓1Sgd pthbj aqnvm enw itlor nudq sgd kzyx cnf.

↓2Rfc osgai zpmul dmv hsknq mtcp rfc jyxw bme.

↓3Qeb nrfzh yoltk clu grjmp lsbo qeb ixwv ald.

↓4Pda mqeyg xnksj bkt fqilo kran pda hwvu zkc.

↓5Ocz lpdxf wmjri ajs ephkn jqzm ocz gvut yjb.

↓6Nby kocwe vliqh zir dogjm ipyl nby futs xia.

↓7Max jnbvd ukhpg yhq cnfil hoxk max etsr whz.

↓8Lzw imauc tjgof xgp bmehk gnwj lzw dsrq vgy.

↓9Kyv hlztb sifne wfo aldgj fmvi kyv crqp ufx.

↓10Jxu gkysa rhemd ven zkcfi eluh jxu bqpo tew.

↓11Iwt fjxrz qgdlc udm yjbeh dktg iwt apon sdv.

↓12Hvs eiwqy pfckb tcl xiadg cjsf hvs zonm rcu.

↓13Gur dhvpx oebja sbk whzcf bire gur ynml qbt.

↓14Ftq cguow ndaiz raj vgybe ahqd ftq xmlk pas.

↓15Esp bftnv mczhy qzi ufxad zgpc esp wlkj ozr.

↓16Dro aesmu lbygx pyh tewzc yfob dro vkji nyq.

↓17Cqn zdrlt kaxfw oxg sdvyb xena cqn ujih mxp.

↓18Bpm ycqks jzwev nwf rcuxa wdmz bpm tihg lwo.

↓19Aol xbpjr iyvdu mve qbtwz vcly aol shgf kvn.

↓20Znk waoiq hxuct lud pasvy ubkx znk rgfe jum.

↓21Ymj vznhp gwtbs ktc ozrux tajw ymj qfed itl.

↓22Xli uymgo fvsar jsb nyqtw sziv xli pedc hsk.

↓23Wkh txlfn eurzq ira mxpsv ryhu wkh odcb grj.

↓24Vjg swkem dtqyp hqz lworu qxgt vjg ncba fqi.

↓25Uif rvjdl cspxo gpy kvnqt pwfs uif mbaz eph.

How the Caesar cipher works

The Caesar cipher is one of the oldest encryption techniques: each letter is shifted a fixed number of places down the alphabet, so with a shift of 3, A becomes D and Z wraps around to C. Because there are only 25 useful shifts, it is trivial to break — the solver above lists every decoding so you can spot the readable one. Letter case is preserved and non-letters pass through untouched.

A shift of 13 is the special case known as ROT13. For real keyword-based encryption, step up to the Vigenère cipher. Everything is computed locally in your browser.

Built and maintained by Meet Shah · Last updated 19 July 2026

What this tool is used for

Solving a puzzle by trying each of the twenty-five possible shifts until the text reads properly.
Teaching the idea of a key by showing exactly what changes when the shift changes.
Lightly obscuring an answer where the reader is expected to work it out themselves.
Checking whether a string is a shifted version of otherwise readable text.
Reproducing a classical example where the shift is historically three.

Frequently Asked Questions

How does the Caesar cipher work?: Every letter moves a fixed number of places through the alphabet, wrapping at the end. A shift of 3 turns A into D. The shift is the entire key, which is why there are only 25 useful ones.
How is it broken?: By trying all 25 shifts, which takes seconds by hand, or by frequency analysis — the most common letter in English ciphertext is usually a shifted E. It offers no real security against anyone who recognises it.
What happens to numbers and punctuation?: They pass through unchanged, which also leaks structure: word lengths and punctuation stay visible, giving an attacker a strong head start even before the shift is guessed.
How does it relate to ROT13?: ROT13 is a Caesar cipher with a shift of 13. Because 13 is half of 26 it is its own inverse, which is why the same operation both encodes and decodes.
Is it useful for anything today?: Teaching and puzzles. It introduces keys, ciphertext and frequency analysis clearly, which is why it survives in courses long after it stopped protecting anything.

Common errors and gotchas

Treating it as security. There are only twenty-five keys, and trying all of them is instantaneous.
Expecting digits and punctuation to shift. Only letters move, which leaves the word shapes fully intact.
Forgetting that a shift of thirteen is ROT13, so encoding and decoding become the same operation.
Using a shift of zero or twenty-six and reporting the tool did nothing, when that is arithmetically correct.
Assuming the shift maps non-Latin letters, which are left untouched regardless of the amount.