It will work for both Sentry Mode and TeslaCam footage.

Sentry Mode and TeslaCam videos have provided remarkable insight into people’s behaviors towards Tesla cars, which range from the amusing to the downright despicable; many such videos went viral. Now the manufacturer has made the viewing of such videos even easier via a recent software update that now gives the option to watch footage captured by the car in the car (Dashcam Viewer).

In case the distinction is not clear, TeslaCam is the in-built dashcam feature that captures footage while the car is being driven. Sentry Mode activates when the car is stationary and it’s being tampered with. And now you can just watch whatever it captured right on its infotainment screen, instead of having to load the footage onto a flash drive in order to watch it on another device.

Tesla details the changes software version 2020.12.5 brings:

'Watch Saved Dashcam clips or Sentry Mode events directly from the touchscreen with the Dashcam Viewer. To launch, tap the Dashcam icon in the status bar and select ‘Launch Viewer’ while the car is in PARK. If the car is in DRIVE, you will continue to save a clip by tapping the icon.

To view saved clips and events stored on your USB drive, tap the Menu icon in the upper left corner of the viewer. Each video is organized by location, date, and thumbnail for easy access. For additional filtering options, tap the ‘Dashcam” or ‘Sentry’ tabs.

Select a clip or event to play the corresponding video. To select video from a particular camera, tap the associated thumbnail marked Front, Rear, Left, or Right. Play pause or scroll by using the video controls at the bottom of the player. To delete a video, tap the trash icon in the bottom right corner of the video player.'

Keep in mind that you still need to have some sort of storage medium plugged into the car (flash drive or an SSD) for this new easier viewing to work. The change brought about by this software update specifically makes things easier because you no longer have to take it out of the car, thus saving you time and hassle.

Source: Tesmanian