Most small digital clocks are mains-powered (plug-in) and offer optional battery backup to preserve time and settings during power outages. Backup batteries vary by model (examples include a single 9V or AAA cells). Note that some units require batteries only for backup, while others may list battery operation as a required power method.

Some small digital clocks include extras like ceiling or wall time projection (often with adjustable projection arms) and on-screen calendar displays that show day, month and date in addition to the time. Other models may add similar display-focused features to enhance visibility or information at a glance.

Small digital clocks typically use LED or LCD displays. Many LED models advertise large 1.8" digit heights, while some LCD models list around 1" digits — choices that affect visibility and power use.

Brightness options range from simple high/low dimmer switches to multi-level dimmers. Some models offer only selectable high/low settings, while others provide three or more adjustable brightness levels for nighttime or daylight viewing.

Common features include a basic alarm with a snooze function, dual alarms on some models, adjustable snooze timers, and volume controls such as high/low settings or ascending alarms to ease wake-up.

Some small digital clocks include a USB charging port for phones and devices. A few models market these as a 2 AMP (or “2 AMP rapid charge”) USB port to indicate faster charging capability.