The "Dark mode" feature that YouTube offered enables users to change the interface to a darker color scheme that is easier on the eyes, especially in low light. When YouTube's Dark Mode is activated, the interface's background is dark and the text and icons are lighter in color. There may be a number causes for YouTube's automatic transition back to light mode, including the following:
Cache and Cookies: When you clear the cookies and cache in your browser or YouTube app settings, your choices can get reset, returning the mode to its original state, which is typically light mode.
Browser Add-ons or Extensions: A few add-ons or browser extensions may interact with YouTube's settings and cause the mode to abruptly flip.
A/B testing on YouTube: On a select group of users, YouTube occasionally tries various features and designs. You might notice changes in the mode if you're a member of such a test group even when the setting hasn't been changed directly.
Try the following to confirm that Dark mode is still available: If you like to use Dark mode across different apps, make sure the setting is enabled on your device. Make sure you have specifically selected Dark mode in your YouTube settings by checking your options. If you don't want your preferences to be reset, avoid emptying your cache and cookies.