Scrcpy 4.0 migrates to SDL3, adds flex displays and camera controls

Genymobile’s Android screen-mirroring tool scrcpy has shipped version 4.0, headlined by a migration from SDL2 to SDL3. The switch brings active upstream maintenance and unlocks new windowing behavior, most notably native aspect-ratio locking during resize that eliminates the black borders previous versions had to draw. Users who prefer the old free-resize behavior can opt out with —no-window-aspect-ratio-lock.

The release introduces flex displays via —flex-display (-x), letting a virtual Android display resize dynamically with the client window, which pairs well with the new —keep-active flag that signals user activity without touching global device settings. Camera control gains runtime shortcuts and CLI flags for torch toggling and zoom, and the default UI gets minor polish: a dark-gray background (configurable via —background-color), a disconnected icon shown for two seconds before the window closes, F11 for fullscreen, and Mod+Q to quit.

Under the hood, the team bumped FFmpeg to 8.1.1, SDL to 3.4.8, dav1d to 1.5.3, and platform-tools to 37.0.0. Notable fixes include a Meta Quest flickering workaround, corrected copy-paste on rooted devices, mDNS-based TCP device detection, UTF-8 console output on Windows, and a curious CPU-usage bug where silent OPUS audio triggered denormal numbers that slowed resampling roughly 40x — patched upstream in FFmpeg.