Use the free XOR Cipher Encoder below: your data never leaves your browser — all work happens on your device, and nothing is uploaded to any server.
One operation, used everywhere
XOR, short for “exclusive or”, is one of the simplest operations in computing: it compares two bits and returns 1 only when they differ. It is also one of the most widely used, sitting inside stream ciphers, checksums, graphics and error correction. This tool shows XOR at its most direct: your text is combined byte by byte with a repeating key, and the result is shown as hexadecimal, a compact form that can be copied, stored and pasted back for decryption.
Using it is straightforward. Type your text, enter a key, and choose Encrypt to hex or Decrypt from hex. Encryption turns “hello” with a key into a hex string; decryption takes that hex string and the same key and returns the original text. Everything runs in your browser, and nothing is sent anywhere.
How the key repeats
The key is applied one byte at a time and starts again when it runs out, so a three-letter key encrypts the fourth character with the first key letter again. That repetition is the whole mechanism and also the whole weakness, explained below. Keys are case-sensitive: “Key” and “key” give different results, so decryption needs the exact key, including capitals. The tool works byte by byte on the character codes of your text, which keeps the behaviour predictable for the plain Latin text this tool is designed for; unusual characters outside that range may not round-trip exactly, so stick to ordinary letters, digits and punctuation for puzzles.
A toy cipher, not secure encryption
This must be said clearly: XOR with a short repeating key is not secure, and must never protect real secrets such as passwords, financial details or private messages. With enough ciphertext, the repeating key leaks patterns, and classic techniques recover both the key length and the key itself. Even a long key is only truly safe in the one-time-pad form, where the key is random, as long as the message, and never reused, conditions this tool does not enforce and a casual user will not meet. If something genuinely needs to stay secret, use a modern, well-tested encryption tool, not a browser toy. This tool exists for learning, puzzles and light obfuscation, such as hiding a spoiler or an answer key from a casual glance.
Reading the hex output
Encrypted output is shown as hexadecimal because raw XOR bytes are often unprintable control characters that cannot be copied reliably. Each byte becomes two hex digits, so “A” with key “k” becomes “2a”. Hex is easy to copy into a message, a document or a puzzle page, and pasting it back with the same key restores the text. If decryption gives you gibberish, the usual cause is a wrong key or a hex string with a missing digit: hex must always have an even number of digits, and the tool reports invalid input instead of guessing.
Practical uses
Teachers demonstrate how stream ciphers combine a keystream with plaintext. Puzzle makers hide answers that readers reveal with a given key. Hobbyist programmers learn how XOR underpins real systems before studying proper cryptography. Game masters obfuscate clues that players decode at the table. Each use benefits from the same property: XOR is reversible with the same key, so one operation does both jobs, and the mechanism is simple enough to verify by hand on a short example.
Privacy note
Your text and key never leave your device; the computation happens in the browser tab. That privacy is real but narrow: it protects you from the tool, not from anyone who sees the hex output and the key together. Treat XOR output as obscured, not encrypted, and never share the key alongside the ciphertext for anything that matters.
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