Optimizely Forms provides an option to redirect to a specified page after a successful submit. The extra info is provided so a page can tailor messaging or behaviours according to the submitted form or data. This is a nice feature that allows a personal experience. It can also allow a developer to use one page type to handle multiple types of submitted forms. After submission, the extra form information is added to the URL as extra parameters. This means the URL gets messy when you redirect. Thankfully, you can use the Optimizely Forms API to omit the extra info if you want a cleaner URL.
Read my post, Hide Optimizely Form Info when Redirecting for more information on my approach. Also, leave a comment below with questions or more information.
