What does “dragging the shutter” mean in photography?

“Dragging the shutter” means using a slower shutter speed than you otherwise would, most often when shooting with flash. The idea is to let more ambient light record during the exposure while the flash briefly lights your main subject.

Why use it:

• brighten a dark background
• balance flash-lit subjects with room or street light
• make the image look more natural instead of “flashy”

How it works:

• the flash burst is very brief and can effectively freeze the subject it lights
• the longer shutter time allows existing light to continue exposing the scene, especially the background

Trade-offs:

• more ambient light can also mean more motion blur or camera shake
• this can happen unintentionally in some auto or aperture-priority situations when the camera chooses a slow shutter speed with flash
• with typical focal-plane shutters, normal flash sync limits shutter speed to around roughly 1/100–1/200 second unless special flash modes are used

In short: dragging the shutter is a deliberate slow-shutter, flash-assisted technique used to mix flash with ambient light more effectively.