What is the difference between buffered and unbuffered channels in Go?

Unbuffered channels require that data sending and receiving occur synchronously. The sender is blocked until the receiver is ready to accept the data, and vice versa. Their buffer size is zero.

Buffered channels have a finite buffer size. The sender is blocked only if the buffer is full, and the receiver — if the buffer is empty.

// Unbuffered channel
unbufferedChan := make(chan int)

// Buffered channel with buffer size of 5
bufferedChan := make(chan int, 5)

Characteristic	Unbuffered channel	Buffered channel
Buffer size	0	> 0
Synchronization	Synchronous interaction	Asynchronous if buffer not full/empty
Sender blocking	Until received by receiver	Until buffer is filled
Receiver blocking	Until sent by sender	Until buffer is emptied

Unbuffered channels are used for goroutine synchronization and to ensure messages are not lost. Buffered channels are used to reduce blocking, allowing the sender to continue working while the receiver is not yet ready, or vice versa.