A security camera is an unusual storage workload. A phone writes in bursts; a camera writes continuously, overwrites the same cells repeatedly in loop recording, and often runs hot. That combination kills cheap cards, and the failure is quiet — the camera looks fine until you go to retrieve footage that was never written.
Capacity: check the camera's limit first
Every camera has a maximum supported capacity, and exceeding it usually produces a card that mounts and then fails on write rather than a clear error. Across the XCAM range this runs from 32GB on the smallest models to 512GB on the 4K models. Check the specification before buying — a 256GB card in a 32GB-limit camera is wasted money and an unreliable recording.
How much footage fits
| Resolution | Approx. per hour | On a 128GB card |
|---|---|---|
| 1080P | ~1GB | ~5 days continuous |
| 1296P | ~1.5GB | ~3.5 days continuous |
| 4K | ~4GB | ~1.3 days continuous |
Motion-triggered recording stretches these dramatically — often by 10× or more, depending on how busy the scene is.
Speed class is the specification that matters
Ignore the headline "up to 100MB/s" read speed on the packaging; that is read, not write, and cameras only write. Look instead for the U1/U3 and V10/V30 marks, which guarantee sustained minimum write speeds of 10MB/s and 30MB/s respectively. For 1080P, U1/V10 is adequate. For 4K, use U3/V30 — a slower card causes dropped frames that show up as stuttering or missing seconds.
Endurance matters more than speed
Standard cards are rated for a modest number of write cycles. Loop recording rewrites the same card constantly, so a normal card in a continuously recording camera can fail within months. Cards marketed as "high endurance" use different NAND and are specifically designed for dashcams and security cameras. They cost slightly more and last considerably longer — this is the single best value upgrade for a camera that runs continuously.
Format in the camera, not the computer
Cameras generally expect FAT32 or exFAT with a specific allocation setup. Formatting on Windows or macOS frequently produces a filesystem the camera mounts but cannot write to reliably. Always format using the camera's own menu, and reformat every few months — it clears the fragmentation that builds up under loop recording.
Counterfeits are common
Fake high-capacity cards are widespread on marketplaces. They report a large size to the operating system but physically contain far less, so writes past the real capacity silently vanish — catastrophic for a security camera. Buy from a reputable seller, and verify a new card with a capacity-testing tool before trusting it.
Choosing a camera as well? See our mini security camera buying guide.