See for example this google query for wikipedia; the first result has both sitelinks and a search box to search within the website.My site only has sitelinks. Is there anything I can do to make the search box appear?
My website has sitelinks but doesn't have a search box below it; is there anything I can do?
seo;google;sitelinks
I think that the search box appears at the discretion of Google and their algorithms, but I have heard that having a CSE set up for your site can increase the likelihood that the box will appear, though this hasn't helped with any of my sites. 