When was the violin shoulder rest invented?

The violin shoulder rest was invented in the 1800s, but the exact year is not known. The first known recorded use of a shoulder rest was by the violinist Louis Spohr in 1820, but it is possible that other musicians were using them earlier. The shoulder rest was originally invented to help violinists who were experiencing discomfort or pain from holding the violin in the traditional way, but it has also become a popular accessory for violinists of all levels, as it can help to improve their playing technique and posture.