How does the rail fence cipher work?

The text is written diagonally across a set number of rows (rails) in a zig-zag, then read off row by row. It is a transposition cipher: the letters are rearranged rather than replaced.

Why must I use the same rail count to decrypt?

The rail count defines the exact zig-zag path. Decrypting with a different number of rails produces gibberish, so encoder and decoder must agree on it.

No — the cipher runs entirely in your browser and nothing is sent to a server.

Rail Fence Cipher Encoder & Decoder

Zig-zag transposition cipher with a choice of rails.

Rail fence cipher encoder and decoder

The rail fence cipher is a classic transposition cipher: your text is written in a zig-zag across a chosen number of rows, or rails, then read off one row at a time. The letters are rearranged rather than substituted.

Choose encrypt or decrypt, set the number of rails, and type your text — the output updates instantly, all inside your browser.