What Is Dash Cam Loop Recording and How Does It Work?

If you've set up a dash cam and looked at the settings, you've seen "loop recording." It's on by default in almost every camera. Most drivers enable it without fully understanding what it does. Here's exactly how it works, why it matters, and what you should know about configuring it.

The Basic Concept

A dash cam records continuously. Left unchecked, it would fill the SD card completely and then stop recording — at which point you'd need to manually delete footage to continue. That's not practical for a camera you want running constantly without attention.

Loop recording solves this by dividing the recording into fixed-length segments and continuously overwriting the oldest segments when the card is full. Think of the SD card as a circular buffer: new footage writes in, old footage gets overwritten, the card never fills completely, and the camera never stops recording.

How Loop Segments Work

Most dash cams allow you to choose the loop segment length: typically 1, 3, or 5 minutes. This means recordings are split into individual files of that duration rather than one continuous file.

Why segment lengths matter:

• 1-minute segments: More granular — you get exactly the relevant minute of footage. But more total files to manage.
• 3-minute segments: The most common default and a good balance for most users.
• 5-minute segments: Larger files, fewer of them. Easier to handle if you're regularly reviewing footage, but you get more context than you probably need for any given event.

When the SD card fills, the camera overwrites the oldest segment first. So the card always contains the most recent footage from the past several hours — the exact amount depends on card size, resolution, and bitrate settings.

What Happens During an Incident: Event Files

The obvious problem with loop recording: what if the footage you need is overwritten before you can retrieve it?

Dash cams address this with event recording (sometimes called "emergency recording" or "locked clips"). When the camera's G-sensor detects an impact — a collision, hard brake, or sudden movement — it automatically flags the current segment as an event file and marks it as write-protected. Write-protected files don't get overwritten during normal loop operation.

Similarly, most cameras let you manually press a button to flag a recording as protected. You can also trigger event files via the companion app.

Event files accumulate in a separate folder (usually called "EVT" or "LOCK") on the SD card. These don't overwrite automatically. Left unmanaged, event files can eventually fill the remaining card space and stop new events from being protected — some cameras warn you, others just silently stop writing new event files. Check your event folder periodically and archive files you want to keep.

Cloud Backup and Loop Recording

For cloud-connected cameras like Nexar, event files are automatically uploaded to the cloud rather than relying on the local SD card alone. This removes the most significant vulnerability of SD-only loop recording: that an important clip might be overwritten or the card might be damaged before you retrieve it.

With cloud backup, the workflow is: collision occurs → G-sensor triggers event file → event file is automatically uploaded to cloud within minutes → you receive a push notification. The local SD card copy is still there, but you already have a secure backup before you've even pulled over.

How Much Footage Does Your Card Hold?

The capacity depends on three variables: card size, recording resolution, and bitrate. As a rough guide for a single-channel front camera:

• 32GB at 1080p: Approximately 3–4 hours of continuous footage
• 64GB at 1080p: Approximately 6–8 hours
• 128GB at 1080p: Approximately 12–16 hours
• 64GB at 1440p: Approximately 4–5 hours
• 128GB at 4K: Approximately 4–6 hours (4K files are significantly larger)

Dual-channel cameras (front and rear) halve these estimates — two cameras writing simultaneously use twice the storage.

Common Loop Recording Mistakes

Not formatting the card before use. A card that's been used in a computer, phone, or other device may have a file system format incompatible with your camera. Format the card in the camera itself (or to FAT32/exFAT as appropriate) before first use.

Using consumer SD cards. Standard cards aren't designed for the continuous write cycles of a dash cam. Use a high-endurance card — Samsung PRO Endurance, Lexar Endurance, SanDisk High Endurance. A consumer card may fail within months under continuous loop recording conditions.

Never clearing event files. If you never archive or delete locked event files, they fill the reserved space on the card and new events stop being protected. Review your event folder monthly.

Assuming the camera is recording. Check the recording indicator (usually a red LED or a flashing icon on the screen) when you get in the car. A full event folder, a corrupted card, or a power issue can stop recording without obvious signs.

The Bottom Line on Loop Recording

Loop recording is what makes a dash cam practical for continuous use — without it, you'd need to manually manage storage on a daily basis. The system works well when it's properly configured: the right card, periodic event file management, and a camera with automatic event protection.

If you're using a cloud-connected camera, the loop recording system is backstopped by automatic cloud upload of critical events — which means even if the loop overwrites footage before you check the card, the important clips are already secured.