It is a filter in Douyin.

Steps to add filters to Douyin shooting: First open Douyin and click the + at the bottom.

Then tap the capture button at the bottom.

After shooting the video, click "Filter" in the upper right corner.

Then select the filter you need below. You can choose portrait, landscape, food, and cutting-edge. Slide the white slider below to set the filter strength.

After selecting the filter, click on the lower screen and then click "Next".

Finally, click "Publish" in the lower right corner.