Does Goodsize drive users outside of my website?

In short the answer is No.

All your clients/users are kept on your website. we use an I-frame pop-up page that allows users to input their size and generate an accurate comparison while browsing for clothes on your website.

This approach is similar to that of other applications used on e-commerce stores, non invasive and discreet, effectively retaining users on your site and enhancing their buying experience.