Up until this point, there’s no official so called “Dark Mode” or “Night Mode” feature on Gmail for both desktop and app.
Fortunately, we can take advantage of one feature on the service which we can use to mimic a similar visualization like a dark mode.
Here, how to enable dark mode on Gmail desktop.
1. Launch Gmail.
2. Head to the Settings > Themes.
3. Select Dark (you may also choose other color that dark enough for you).
4. Save the new theme.
5. Now the Gmail appearance will look darker.
Some areas such as the Compose and mail section may still look bright. I highly suggest you use a Chrome extension named Dark Reader.
This extension will truly enable dark mode on any website you visit, including Gmail. It can also be combined with the Dark theme you choose before. For even better visual experience, check out How to Enable “True” Dark Mode on Chrome PC.