I implemented a Google Sitelinks Searchbox on my home page. I've checked https://developers.google.com/search/docs/data-types/sitelinks-searchbox and it doesn't mention which format I should use for the results page.
Which Schema.org type can be used for my own SERPs? Should I use an XML sitemap, JSON-LD, Microdata?
You can use the SearchResultsPage
type.
Each result could be a WebPage
(or a more specific type, like ItemPage
if it applies).
To connect the SearchResultsPage
with the WebPage
results, you can use the mainEntity
property with an ItemList
value. You can find RDFa examples in this answer.