Quality Assurance is a free Chrome add-on developed by logan. It is a JavaScript utility that allows users to measure the spacing and styles between elements on a webpage. This tool is particularly useful for web developers and designers who need to ensure the accuracy of their layout and design.

To use Quality Assurance, simply hold down the Alt key on Windows or the ⌥ Option key on Mac and move the cursor over an element on the webpage. The add-on will show you detailed information about that element, including its spacing and styles. This feature allows you to easily identify any inconsistencies or issues with your webpage's layout.

Additionally, Quality Assurance offers the ability to compare the spacing and styles between two elements. By holding down the Alt key and clicking on one element, then moving the cursor to another element, you can quickly see the differences in spacing and styles between the two elements.

Overall, Quality Assurance is a handy tool for anyone involved in web development or design. Its ability to measure and compare spacing and styles on webpages makes it a valuable asset for ensuring the quality and accuracy of your work.