When works are marked with code generated by the Creative Commons License Chooser, that mark is machine readable. A number of search tools allow users to limit their search by license.
All of the following platforms host materials that have been licensed under Creative Commons licenses or are in the public domain. They allow users to search for works by license. Most of the platforms also host materials that have not been licensed under any open license.
The sites below offer images that are licensed for reuse or are in the public domain. The Images research guide provides a more comprehensive list of such sites.