A dashcam's storage works fundamentally differently from a regular camera or phone — understanding loop recording explains both its convenience and its biggest risk.
Loop recording
A dashcam continuously records in short segments (often 1-3 minutes each) and automatically overwrites the oldest segments once the storage card fills up, cycling through in a loop rather than stopping when full. This means a dashcam never needs manual file management under normal use — but it also means footage from days or weeks ago is almost certainly gone unless it was specifically protected, since it's been recorded over by newer footage in the ordinary loop.
The lock feature is what actually saves footage that matters
Most dashcams include a "lock" or "protect" function, triggered either manually or automatically by a built-in impact sensor (G-sensor) detecting a sudden jolt consistent with a collision. Locked or protected clips are moved to a separate storage area that the normal loop-recording overwrite process skips, preserving that specific footage until it's manually deleted. Without this feature actually working and being used, footage from an actual incident can be overwritten within hours if the dashcam keeps running afterward — this is the single most important feature for a dashcam's actual real-world purpose.
Storage card requirements are stricter than for normal photo storage
Dashcams write and overwrite data constantly and heavily, which is a much more demanding workload than a card used for occasional photo storage. Using a card not specifically rated for continuous, high-endurance recording can lead to premature card failure or corrupted footage — checking that a memory card is rated for dashcam or security-camera-style continuous use, not just a high storage capacity, matters more than capacity alone.
Resolution and low-light performance are a real tradeoff
Higher resolution captures more detail, useful for reading license plates or fine details after an incident, but produces larger file sizes that fill storage faster and can strain processing in low light. A dashcam's actual low-light performance — critical for capturing usable footage at night — varies significantly between models regardless of stated resolution, and is worth checking in real-world sample footage rather than assuming higher resolution alone guarantees better night performance.
The one thing people forget
Check local laws regarding dashcam audio recording and windshield mounting placement before installing one — some jurisdictions have specific rules about consent for audio recording or restrictions on where a device can be mounted on the windshield, and these vary enough by location that it's worth a quick check rather than assuming dashcam use is unrestricted everywhere.