How to Use
- 1.
Choose Caesar Cipher or the ROT13 quick option.
- 2.
Select Encrypt or Decrypt, then paste or type text in the input area.
- 3.
For Caesar Cipher, set a shift from 1 to 25 and choose forward or backward direction.
- 4.
Choose whether to preserve letter case or rotate digits; punctuation stays unchanged.
- 5.
Review the live output, cipher wheel, mapping table, and letter frequency chart.
- 6.
If the key is unknown, open Brute Force or run Auto Detect, then copy, swap, or download the result.
Features
Caesar cipher encrypt and decrypt modes
ROT13 one-click encoder and decoder
Shift slider and number input
Forward and backward alphabet direction
Optional case preservation
Optional digit rotation
Real-time browser output
All 25 brute-force decryptions
Heuristic English shift detection
Letter frequency analysis
Interactive alphabet cipher wheel
Side-by-side mapping table
Copy output and individual candidates
Swap input and output
Download result as TXT
Client-side privacy
Responsive mobile interface
No signup required
Frequently Asked Questions
What is a Caesar cipher?+
A Caesar cipher substitutes each letter with a letter a fixed number of alphabet positions away. The shift wraps at the end of the alphabet.
How do I decrypt a Caesar cipher?+
Choose Decrypt and enter the shift used during encryption. If the shift is unknown, review all 25 Brute Force candidates or try the English auto-detection helper.
What is ROT13?+
ROT13 is a Caesar cipher with a fixed shift of 13. Because the English alphabet has 26 letters, applying ROT13 a second time restores the original text.
Is Caesar cipher secure encryption?+
No. It has very few possible keys and can be broken immediately by brute force. It is suitable for education, puzzles, and light obfuscation only.
What happens to spaces and punctuation?+
Spaces, punctuation, emoji, and other non-Latin characters remain unchanged. You can optionally rotate digits from 0 through 9.
Does the tool preserve uppercase and lowercase letters?+
Yes when Preserve letter case is enabled. When disabled, transformed Latin letters are normalized to uppercase.
How does automatic shift detection work?+
It compares every possible decryption with common English letter frequencies and word patterns. It is a heuristic and can be inaccurate for short or non-English text.
What does brute-force mode do?+
It applies every possible Caesar decryption shift from 1 to 25, letting you inspect and select the readable candidate without knowing the key.
Can this tool decrypt modern encryption?+
No. It only handles simple Caesar alphabet shifts and ROT13. It cannot decrypt AES, RSA, password hashes, or other modern cryptographic formats.
Is my text uploaded to a server?+
No. The cipher, analysis, copying, and TXT export run in your browser, so entered text is not sent to WebToolsEdge for processing.
About this tool
Free Caesar Cipher Encrypt and Decrypt
Use the free WebToolsEdge Caesar Cipher Encrypt and Decrypt tool to shift letters forward or backward through the alphabet. Choose any Caesar shift from 1 to 25, switch between encryption and decryption, or select ROT13 for a fixed 13-letter transformation. The output updates instantly and remains on your device. How a Caesar Cipher Works A Caesar cipher replaces each letter with another letter a fixed number of positions away. With a forward shift of 3, A becomes D, B becomes E, and X wraps around to A. Decryption applies the opposite movement. The interactive cipher wheel and alphabet mapping table show exactly how the current transformation changes every letter. Caesar Cipher Encrypt and Decrypt Modes Encrypt mode transforms readable plaintext into shifted ciphertext. Decrypt mode reverses a known shift. Select forward or backward direction when a puzzle or legacy system defines its shift in the opposite direction. Letter case can be preserved, while punctuation and symbols remain unchanged. An optional digit control rotates numbers from 0 through 9 using the same shift. ROT13 Encoder and Decoder ROT13 is a special Caesar cipher with a fixed shift of 13. Applying ROT13 twice returns the original text, so the same operation encodes and decodes it. It is useful for light obfuscation, spoilers, puzzles, and demonstrations, but it is not secure encryption. Brute-Force Caesar Cipher Decoder If the shift is unknown, Brute Force displays all 25 possible Caesar decryptions. Review the candidates and use the readable result. This works because a traditional Caesar cipher has only 25 non-trivial letter shifts, making it unsuitable for protecting confidential information. Automatic Shift Detection Auto Detect scores all possible decryptions using common English letter frequencies and words. It can provide a useful starting point for normal English sentences, but it may be wrong for short text, names, code, abbreviations, or another language. The tool reports the result as a likely shift rather than a guaranteed answer. Letter Frequency Analysis Frequency analysis counts how often A through Z appear in the current output. Longer English ciphertext often retains recognizable statistical patterns, which can help students understand classical cryptanalysis and compare possible decryptions. Privacy and Security All transformations, brute-force candidates, detection, copying, and downloads run locally in your browser. Caesar cipher and ROT13 provide obfuscation only. Never use them to protect passwords, API keys, financial records, private messages, or other sensitive information; use modern, reviewed cryptography for real security. Related Text and Developer Workflows After decoding text, use Text Diff Checker Online to compare versions, Find and Replace Text Online to clean repeated patterns, or Text Space Cleaner to normalize copied content. URL Encoder Decoder is the appropriate related utility when reserved URL characters need percent encoding rather than alphabet substitution.