Coding Events: Triggers and Responses

In Scratch, an event is something that happens to start or change a program. Events are triggers — they are the "if this happens" part of a rule. When an event occurs, the connected script (the response) runs. Events make programs interactive because they let the program react to what the user does.

Common Scratch Event Blocks

• "When green flag clicked" — the most common trigger; starts the program.
• "When [space/arrow/letter] key pressed" — triggers a script when a keyboard key is pressed.
• "When this sprite clicked" — triggers a script when the user clicks on the sprite.
• "When backdrop switches to [backdrop name]" — triggers when the background changes.
• "When loudness > [number]" — triggers when a sound (microphone) gets loud enough.
• "When I receive [message]" — triggers when another sprite sends a broadcast message.
• "When timer > [number]" — triggers when the built-in timer goes past a set number.
• "Broadcast [message]" — sends a message that can trigger another sprite's script.

How Events Work

Think of events like light switches: the switch (trigger) is connected to the light (response). When you flip the switch, the light turns on. In Scratch, clicking the green flag is the switch and the script below it is the light. You can have many different switches — each one starts a different part of your program.