Contact Form 7 is the more common of the two in our index: it runs on 910 websites against 99 for EWWW Image Optimizer, and 21 sites use both. Counts come from real scans, not vendor claims.
Contact Form 7 is an WordPress plugin which can manage multiple contact forms. The form supports Ajax-powered submitting, CAPTCHA, Akismet spam filtering.
EWWW Image Optimizer is an image optimisation WordPress plugin designed to improve the performance of your website.
21 sites run both Contact Form 7 and EWWW Image Optimizer. That is 21% of the sites using EWWW Image Optimizer, the smaller of the two.
Want to know which one a particular site uses? Look it up and see its whole stack, or compare two sites side by side.