The SlimeVR Butterfly Trackers are ultra-slim, full-body motion capture and VTubing devices that rely on IMUs and a dedicated 2.4 GHz ESB dongle for host communication, avoiding base stations or Wi-Fi.

The article is authored by Debashis Das, a technical writer and embedded engineer, who provided context and links to related repositories and documentation.

Each tracker delivers over 48 hours of active use per charge, supports USB‑C charging, includes deep sleep standby, and offers an optional 10‑tracker charging dock, with certifications in progress for FCC and CE.

Availability and pricing are listed on Crowd Supply, with bundles ranging from a Core Set at $279 to a 17‑tracker Motion Capture Set at $788, plus upgrade packs, dongles, and accessories; shipping is slated to begin on August 31, 2026.

The hardware centers on a Nordic Semiconductor nRF52833 with a 64 MHz Cortex-M4F, 128 kB RAM, and 512 kB flash, using a 6‑axis IMU (TDK ICM‑45686) and offering 100–200 Hz refresh rates with sub-15 ms latency.

A central SlimeVR Server acts as the brain, capable of handling up to 20 trackers, with OpenVR Driver for SteamVR compatibility and OSC for standalone Quest devices; data is transmitted over the local network to headsets.

Each tracker weighs under 10 grams and measures 56 x 35 x 7 mm, powered by a 90 mAh battery, and employs a split butterfly design with a flexible bridge for improved comfort and body contouring.

The SlimeVR software stack includes Smol Slime firmware, Smol Slime Dongle firmware, and the SlimeVR Server, which process rotation data through Forward Kinematics and a virtual skeleton to enable Autobone and drift-compensation features like Stay Aligned.

Context notes that the Butterfly Trackers use ESB rather than Wi‑Fi to extend battery life, contrasting with the original ESP32/ESP8266‑based SlimeVR trackers that were more power‑hungry but network‑friendly.