Modal window action buttons, top or bottom

1. Where should modal buttons be placed?
2. Should primary CTA be on the left or right?
3. Where should back buttons be?

Where should modal buttons be placed?

In modals and dialogs, align the buttons to the right, or possibly consider a center alignment. Rationale: all major platforms (Windows & macOS) right-align the terminating actions buttons in modals/dialogs, users scan modals in a “Z” pattern (check out the “Gutenberg Diagram”).

Should primary CTA be on the left or right?

Full page designs should have the primary button on the left side of the page. If the browser window is large, or you have to scroll down to fill out a form, it's best to have the primary button right below the last bit of content on the page.

Where should back buttons be?

Right: back button above the form (good). Some forms or questionnaires appear across multiple pages and some people want to go back to check or change their answers.