Many of us have used domain search tools to find interesting names to register. In certain cases, it makes sense to add such a tool to your website (e.g. if you run a website about domaining or web hosts). The WP Domain Checker plugin is a simple tool that allows your visitors to check domain name availability on your site.
The plugin supports top-level and country-code top-level domains. It comes integrated with WHMCS and WooCommerce. You can change button text, link, and other settings in the back-end. Webmasters have the option to use WP Domain Checker with reCAPTCHA.
This AJAXified plugin supports 300+ TLDs. You can customize its colors and use the available widget to add it to your site faster. This is a commercial plugin.