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Gravity Form Square plugin is a WordPress plugin that allows users to pay from their gravity form using Square payment gateway. 
This will help you to add Square payment option to your form created through Gravity Form plugin. So users will be able to pay via Credit Card number 
and this payment will process through your Square account.
<h3>Features</h3>
Easy to setup. 
Admin can authorize his account by one click. . 
Get payment instantly.

Gravity Forms Square (Free)

Gravity Form Square plugin is a WordPress plugin that allows users to pay from their gravity form using Square payment gateway.

rdonk

Square Sync allows you to list you Squareup products on your wordpress page/post(s) via shortcode. The products are listed from the Connect Squareup API and link to the Square Market. As of this version, the Square Market’s payment processing is only available to US customers.

Square Sync

Square Sync lists squareup products from the Connect Squareup API

Gravity Forms Square (Free) vs Square Sync