The short version
Most decks indexed here are released under a Creative Commons license — typically CC BY (attribution), CC BY-SA (attribution + share-alike), or CC BY-NC (attribution + non-commercial). A smaller share are in the public domain (CC0 or by virtue of age). A handful carry "all rights reserved" markings; for those, the deck is preserved by the upstream archive but you should not redistribute or remix without contacting the original creator.
Classroom use
For most academic and classroom uses — projecting a deck in a lecture, citing slides in a course pack, adapting a single diagram for a worksheet — the licenses you'll encounter are permissive and the answer is "yes, with attribution." Treat the contributor name shown on the detail page as the author and link back to the source URL as the citation.
Commercial reuse
If you intend to use a deck in a paid course, a commercial product, or any context where money changes hands, check the license carefully. The "NC" (non-commercial) qualifier is common in educational repositories and prohibits commercial reuse without a separate agreement with the creator. CC BY and CC0 generally permit commercial reuse with attribution; CC BY-SA permits it but requires you to release your derivative under the same license.
Remixing and translating
"SA" (share-alike) decks are excellent base material for translations and adaptations because the only constraint is that your derivative carries the same license. CC BY decks are even more flexible — you can remix freely as long as you credit the original. Decks marked "ND" (no derivatives) can be redistributed in their original form but cannot be modified.
How to cite a deck
A reasonable citation format for a Slide Collection entry, suitable for a syllabus or a worksheet footer, is:
Creator. "Title of presentation." Hosted on Internet Archive (or upstream source). Indexed at slidecollection.com/deck/<slug>.
Always link to the source URL on the detail page, not just to Slide Collection — it's the source URL that points to the actual file and the actual license.
If you spot a license problem
License metadata is messy in the wild. If you find a deck whose license appears to be misstated, or which you believe shouldn't be openly distributed at all, please report it to the upstream archive — we will pick up the correction or takedown on the next refresh.