You can add &interval=30 (milliseconds) to the end of the URL to specify how quickly the image refreshes.
While modern surveillance cameras utilize RTSP, H.264, or H.265, viewerframe mode refresh was a cornerstone of early IP video. viewerframe mode refresh top
Browsers aggressively cache frame data to save bandwidth. A standard refresh might just reload old visual data from the local disk. You can add &interval=30 (milliseconds) to the end