What is the difference between a buffered and unbuffered channel?

Question

Accepted Answer

// Unbuffered — sender blocks until receiver is ready
unbuf := make(chan int)

go func() {
    unbuf <- 42 // blocks here until main goroutine receives
}()
val := <-unbuf // both goroutines rendezvous here
fmt.Println(val)

// Buffered — sender only blocks when buffer is full
buf := make(chan int, 3)
buf <- 1 // non-blocking (buffer has space)
buf <- 2 // non-blocking
buf <- 3 // non-blocking
// buf <- 4 // BLOCKS — buffer full

fmt.Println(<-buf) // 1
fmt.Println(<-buf) // 2
fmt.Println(<-buf) // 3

// Use case: batch job queue
const workers = 5
jobs := make(chan Job, 100) // buffer absorbs bursts

for i := 0; i < workers; i++ {
    go func() {
        for job := range jobs {
            process(job)
        }
    }()
} Unbuffered: guaranteed handoff, synchronization points, request-reply patterns Buffered: decouple producer and consumer speeds, absorb bursts, pipeline stages Buffered channels are NOT a substitute for proper back-pressure — a full buffer that never drains causes goroutine leaks Rule of thumb: start with unbuffered, add buffer only when profiling shows unnecessary blocking Closing a channel signals no more values — receivers drain remaining buffered values before seeing the zero value

What is the difference between a buffered and unbuffered channel?

An unbuffered channel synchronizes sender and receiver — both must be ready simultaneously. A buffered channel decouples them up to the buffer capacity, after which the sender blocks.

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