Why delay() Blocks Everything

The delay function pauses your sketch for a set number of milliseconds. It is the simplest way to slow things down and make a blink visible.

delay(1000) waits one full second, since the value is in milliseconds. So delay(500) is half a second and delay(2000) is two seconds.

The catch: delay freezes everything. While it waits, your board does nothing else at all, like a person holding their breath. 😮

During a delay your board cannot notice a button press. Tap it mid-pause and the press is simply ignored, which feels broken to a user.

Here a one-second delay sits between the checks, so any press in that whole second is lost before the next read happens.

Because delay blocks, you cannot blink an LED and watch a sensor at the same time. The whole sketch waits as one task.

Two delay calls in a row simply add together. Spread several around and your board spends most of its life frozen and unresponsive.

delay is not evil. For a single blinking LED with nothing else going on, it is perfectly clear and totally fine to use.

The real goal is a non-blocking sketch that keeps reacting while it also times events. That means never freezing the loop with a long pause.

Instead of pausing, you can ask how much time has passed and act only when enough has gone by. The loop keeps spinning meanwhile.

Soon you will meet millis, a clock that lets you measure elapsed time without freezing. It is how real projects stay responsive.

What is the main drawback of using delay in a sketch?

You saw that delay is simple but freezes the board, missing inputs and blocking other tasks. Next you will time events without stopping the loop. ✨