Q&A: Are SD and MMC Cards Interchangeable?

Since MultiMediaCards and Secure Digital cards look alike, can I substitute an SD card in place of the MMC card that came in my digital video camera? No one seems to be able to answer that question, including customer service. You can buy SD cards at an attractive price but you seldom see MMC cards on sale at all.

--Harold R. Buehler, New York

You're right, Harold: SD and MMC cards do look a lot alike. But therein lies the problem--they're close, but not identical. They have the same pin connections and identical height and width measurements, but SD cards are 0.7mm thicker than MMC media.

So where does that leave you? Well, you can almost always put an MMC card into an SD slot, but the reverse isn't always true. If you camera's user guide or tech support can't answer your question, my advice is to try it. Borrow an SD card from a friend and give it a shot. Gently insert the card--don't force it! If it slides in and is recognized by the camera, you're in business. Unless you can find your question answered on the Web in a product review or FAQ, there really isn't a good way to tell without actually trying.