What happens to unused synapses during synaptic pruning?

During the process of synaptic pruning, unused synapses are eliminated completely.1

In the developing brain, neurons initially form an excess of connections. As the brain processes sensory information, connections that are not reinforced by sensory stimulation or experience begin to weaken. This pruning process is essential for brain development, as it removes redundant or inactive pathways, ultimately leaving behind efficient, strengthened networks of neural connections. This "pruning back" of excess synapses is a fundamental aspect of neuroplasticity and often occurs most significantly during adolescence.21