Download your favorite font in .ttf format. Backup original fonts in /system/fonts named: Roboto-Regular.ttf AndroidSansMono.ttf Then copy your downloaded font onto that folder. Rename it to DroidSansMono.ttf or Roboto-Regular.ttf Roboto-Regular.ttf works on some app like Chrome, SystemUI, etc. DroidSansMono.ttf works on some text editor apps and some not idk why.