Small font size with 1440p external monitor

Solution 1:

In my experience if you connect your monitor via HDMI it won't give the the font scaling options in System Preferences > Displays.

If however you connect via DisplayPort i.e. Mini DisplayPort to DisplayPort it should give you the options similar to these:

There used to be some hacks to trick the monitor into switching into HiDPI mode but I couldn't personally get these to work on macOS High Sierra, but using a DisplayPort cable rather than either HDMI or Mini DisplayPort to HDMI did resolve the issue.

Solution 2:

My Dell U2719DC does the same.

The best solution for me was using my Mac set to 2048X1152 res since the higher resolution gives me the eye strain. The fonts are tiny too. Though I wish could use the higher res, it's way sharper overall.

Solution 3:

There is a tool called BetterDummy which makes the scaling option available for 1440p monitors: https://github.com/waydabber/BetterDummy