ROT13 & Caesar Brute Forcer
Shift, substitute or Vigenère-encode text in your browser — then break a Caesar cipher with chi-squared scoring against real English letter frequencies.
Alphabet dial
Inner ring = plain alphabet, outer ring = cipher alphabet, pointer = rotation.
Full substitution mapping
| Plain | A | B | C | D | E | F | G | H | I | J | K | L | M |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cipher | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
Letters only: A→N, Z→M. Shift 13 is ROT13, its own inverse.
Brute force — all 26 decryptions of the current cipher text
Ranked by chi-squared distance from standard English letter frequencies (lower is a better fit). The confidence badge uses the ratio between the best and second-best score.
| # | Shift | Plaintext preview | χ² | Copy |
|---|---|---|---|---|
| 1 | 0top 1 | Why did the chicken cross the road? Gur puvpxra pebffrq gur ebnq! | 108.6 | |
| 2 | 1 | Vgx chc sgd bghbjdm bqnrr sgd qnzc? Ftq otuowqz odaeeqp ftq damp! | 845.0 | |
| 3 | 2top 5 | Ufw bgb rfc afgaicl apmqq rfc pmyb? Esp nstnvpy nczddpo esp czlo! | 242.3 | |
| 4 | 3 | Tev afa qeb zefzhbk zolpp qeb olxa? Dro mrsmuox mbyccon dro bykn! | 412.0 | |
| 5 | 4 | Sdu zez pda ydeygaj ynkoo pda nkwz? Cqn lqrltnw laxbbnm cqn axjm! | 539.8 | |
| 6 | 5 | Rct ydy ocz xcdxfzi xmjnn ocz mjvy? Bpm kpqksmv kzwaaml bpm zwil! | 926.6 | |
| 7 | 6 | Qbs xcx nby wbcweyh wlimm nby liux? Aol jopjrlu jyvzzlk aol yvhk! | 412.6 | |
| 8 | 7 | Par wbw max vabvdxg vkhll max khtw? Znk inoiqkt ixuyykj znk xugj! | 597.5 | |
| 9 | 8 | Ozq vav lzw uzaucwf ujgkk lzw jgsv? Ymj hmnhpjs hwtxxji ymj wtfi! | 1003.3 | |
| 10 | 9 | Nyp uzu kyv tyztbve tifjj kyv ifru? Xli glmgoir gvswwih xli vseh! | 280.8 | |
| 11 | 10 | Mxo tyt jxu sxysaud sheii jxu heqt? Wkh fklfnhq furvvhg wkh urdg! | 370.7 | |
| 12 | 11 | Lwn sxs iwt rwxrztc rgdhh iwt gdps? Vjg ejkemgp etquugf vjg tqcf! | 307.7 | |
| 13 | 12 | Kvm rwr hvs qvwqysb qfcgg hvs fcor? Uif dijdlfo dspttfe uif spbe! | 243.7 | |
| 14 | 13top 3 | Jul qvq gur puvpxra pebff gur ebnq? The chicken crossed the road! | 219.9 | |
| 15 | 14 | Itk pup ftq otuowqz odaee ftq damp? Sgd bghbjdm bqnrrdc sgd qnzc! | 623.9 | |
| 16 | 15top 4 | Hsj oto esp nstnvpy nczdd esp czlo? Rfc afgaicl apmqqcb rfc pmyb! | 239.3 | |
| 17 | 16 | Gri nsn dro mrsmuox mbycc dro bykn? Qeb zefzhbk zolppba qeb olxa! | 422.2 | |
| 18 | 17 | Fqh mrm cqn lqrltnw laxbb cqn axjm? Pda ydeygaj ynkooaz pda nkwz! | 538.1 | |
| 19 | 18 | Epg lql bpm kpqksmv kzwaa bpm zwil? Ocz xcdxfzi xmjnnzy ocz mjvy! | 1276.6 | |
| 20 | 19 | Dof kpk aol jopjrlu jyvzz aol yvhk? Nby wbcweyh wlimmyx nby liux! | 341.9 | |
| 21 | 20 | Cne joj znk inoiqkt ixuyy znk xugj? Max vabvdxg vkhllxw max khtw! | 767.9 | |
| 22 | 21 | Bmd ini ymj hmnhpjs hwtxx ymj wtfi? Lzw uzaucwf ujgkkwv lzw jgsv! | 658.5 | |
| 23 | 22top 2 | Alc hmh xli glmgoir gvsww xli vseh? Kyv tyztbve tifjjvu kyv ifru! | 213.6 | |
| 24 | 23 | Zkb glg wkh fklfnhq furvv wkh urdg? Jxu sxysaud sheiiut jxu heqt! | 332.5 | |
| 25 | 24 | Yja fkf vjg ejkemgp etquu vjg tqcf? Iwt rwxrztc rgdhhts iwt gdps! | 355.9 | |
| 26 | 25 | Xiz eje uif dijdlfo dsptt uif spbe? Hvs qvwqysb qfcggsr hvs fcor! | 297.9 |
Frequency analysis — cipher text vs standard English
Comparing the two distributions (Kullback–Leibler style gap against the baseline) is what the shift ranking above automates: an unshifted English text peaks at E/T/A, a Caesar-shifted one at the letters those became.
About this tool
ROT13 & Caesar Brute Forcer encrypts, decrypts and cryptanalyses classical substitution ciphers: shift ciphers (ROT-N, including one-click ROT13), a keyword-shuffled substitution alphabet, and a repeating-key Vigenère cipher. Non-letter characters are always passed through untouched and letter case is preserved, so punctuation, digits and accented text survive round-trips. The brute-force panel decrypts the text at every shift and ranks the results with a chi-squared test against real standard English letter frequencies.
Everything runs entirely in your browser — no text is ever uploaded or sent anywhere, and the tool works offline. Analysis tables are capped for responsiveness: the brute-force preview shows the first 90 characters of each candidate, and shifts are only scored once the text holds at least 8 letters.
Free, no sign-up, no uploads.
- 100% free — no account needed
- Runs in your browser
- Nothing is uploaded
Frequently asked questions
Is ROT13 & Caesar Brute Forcer really free?
Yes. ROT13 & Caesar Brute Forcer is completely free on PureBrowser — every feature, with no account, no trial, and no credit card.
Does ROT13 & Caesar Brute Forcer upload my data?
No. ROT13 & Caesar Brute Forcer runs entirely inside your browser, so anything you type, paste, or open stays on your own device.
Do I need to sign up or install anything?
Neither. There is no account and nothing to download — open the page and ROT13 & Caesar Brute Forcer is ready to use on desktop or mobile.
Does ROT13 & Caesar Brute Forcer work offline?
Once the page has loaded, yes. All of the processing happens locally in your browser, so it keeps working without a connection.
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