JDownloader doesn't yet support HighDPI environments.
Because of this you may experience UI issues such as:
HighDPI support requires a more recent java version (breaks backwards compatibility) and also the used LookAndFeel has to support it (and our current one doesn't fully).
At this moment all you can do is adjust some OS' settings.
In JDownloader:
LAFSettings.fontrespectssystemdpi
-> Restart JDownloaderHints for Windows users
Hints for Mac users
Related tickets:
Tags: Retina, High DPI, HDPI, HiDPI, High-DPI Scaling, scale, scale factor