Yandex Wordstat Assistant is a subscription-based web development tool designed for Firefox users. It facilitates the management of keyword phrases through a user-friendly interface. Users can easily search for and add phrases using the '+' icon or 'add all' link, ensuring a streamlined workflow. The program allows users to copy the generated list of phrases to the clipboard, which can then be pasted into spreadsheet editors like Microsoft Office Excel or OpenOffice Calc for further processing.

This tool supports both old and new Yandex WordStat interfaces and offers features such as automatic duplicate checking and multiple sorting modes, including by addition order, frequency, or alphabetically. Users can also manually add phrases to complement existing lists, with options to highlight previously added words and automatically remove unnecessary characters. The phrase list is preserved upon browser closure and synced across open tabs, enhancing usability.