Encrypt and decrypt with the Playfair digraph cipher using a 5×5 keyword square (I/J merged). Playfair Cipher is a free online tool from the ToolsRift Text Encoding Tools collection. It runs entirely in your browser — nothing to install, no signup, and your data never leaves your device.
A keyword fills a 5×5 grid (I and J share a cell). The message is split into letter pairs; each pair is transformed by the row/column rules — same row shifts right, same column shifts down, otherwise the pair forms a rectangle and swaps columns.
If a pair contains two identical letters (like the LL in HELLO) an X separates them, and a trailing X pads an odd-length message. This is why decrypted text may contain extra X letters where padding was added.
No. J is merged into I before encryption, so decrypted text shows I wherever the original had J. This is standard for the classic Playfair square.