What is the Four-Square Cipher tool?

Encrypts pairs using four 5×5 squares. This free online tool is available at NumbersChecker with no login required.

Is the Four-Square Cipher tool free?

Yes, the Four-Square Cipher tool is completely free to use at NumbersChecker. No account or installation is needed — results are instant.

How do I use the Four-Square Cipher tool?

Enter your input into the form at https://numberschecker.com/tool/four-square, click Run, and the result appears instantly. Click any result value to copy it to your clipboard.

Is there an API for the Four-Square Cipher tool?

Yes. Send a POST request to https://numberschecker.com/api/four-square with your input as a JSON body. The API is free and requires no authentication.

Ciphers digraphkeygrid

Four-Square Cipher

Encrypts pairs using four 5×5 squares.

About the Four-Square Cipher Tool

Encrypts pairs using four 5×5 squares. This free online tool runs entirely in your browser — no login, no installation, and no data is stored.

This tool is part of the Ciphers category on NumbersChecker. Browse all Ciphers tools or explore all 139 tools.

Related: digraph · key · grid

API usage

POST /api/four-square
Content-Type: application/json

{
  "text": "your input here"
}