firmware is through the official Yealink USB Connect tool , which automates the process and provides access to the latest official releases. How to Update Yealink WH66 Firmware
If you need a specific version (e.g., a beta release or a previous version for compatibility), you can perform a manual upgrade.
: If a newer version is found, click Update Now . The process typically takes about 5 minutes, during which the headset must remain in its charging station. Method 2: Manual Firmware Download
: Download the specific .rom firmware file from the Yealink Support documentation page.