PalmRejection

Palm rejection is a feature in touchscreen and digitizer devices that prevents unintentional input from the palm or other resting parts of the hand while a user is writing or drawing. By distinguishing between intentional input from a stylus or finger and unintended contact from the hand, palm rejection enables natural hand rest during use.

Implementation typically combines hardware sensing and software processing. Hardware may include a digitizer that detects contact area, pressure, tilt, and proximity of a stylus, while software analyzes touch events to identify palm-like contact based on large contact areas, slow or stationary movement, and lack of stylus data. In many systems, the stylus is given higher priority; touches that are consistent with a palm are filtered or delayed while a stylus tip-down gesture is active.

Approaches vary: some systems rely on proximity or capacitive sensing to separate pen from palm; others use trajectory and timing models; some devices allow user calibration to improve accuracy. Modern platforms may implement palm rejection as part of a larger input pipeline, integrating with the OS's touch stack and drawing APIs.

Limitations include occasional false positives or negatives, especially for large fingers or errant touches near the stylus. Performance can affect latency, and implementation differences can lead to inconsistent behavior across apps or devices. Palm rejection is commonly used in graphic tablets, stylus-enabled smartphones, and tablets for note-taking and drawing.