Canvas - Certificates
Canvas features optional certificates of completion that are issued automatically when a learner completes a course. They allow staff users to pick from templates defined at a staff level, or to directly input custom HTML and CSS to enable per-course fully custom certificates with fully flexible content, though doing so requires basic HTML knowledge.
A feature that Canvas has which is absent from both Moodle and Open edX is support for automatic certificate expiry. Certificates can be given durations in which they are valid for qualifications where repeated periodic certification is necessary. Canvas also has the concept of program certificates, which are composite certificates formed from the completion of multiple courses.
Canvas also advertises a deep integration with Accredible for more robust certificates and badging than their standard certificates.
Links:
How do I add a certificate of completion for a Catalog course?
How do I add a certificate of completion for a Catalog program?