Camera Viewer is an add-on for Blender that shows a camera preview inside the 3D viewport. You can lock the camera, set the preview position, and apply transformations to the preview while working in the scene.
The add-on includes independent overlay settings with UI buttons to adjust them, along with color management support. A navigation mode inside the viewer lets you move with W, A, S, D, adjust height with E and Q, pan by holding Shift, and change the lens focal length by scrolling, and you can switch between Solid, Material, and Rendered display. The viewer toggles with Alt + F1 and opens for editing with F1, and it is reachable from the View 3D header. Cycles rendering and background images in the camera are not supported, and 1 viewport sample in EEVEE is suggested for better performance.
Camera Viewer runs on Blender 4.4 and newer and is released under the GNU General Public License v3.0 or later. It requires no special permissions.