Classroom Timer

Yes, when you switch to Stages — Classroom's stages default to automatic changes, so the timer moves from Instruction to Independent work to Review on its own as each block's time runs out.

Yes. Fullscreen mode enlarges the countdown for a shared screen or projector, readable from across the room.

A quick single timer is the default — pick a preset or enter a custom duration and press Start. Stages are there when you want a full lesson plan instead, but they're never required.

Yes, and it depends on which of those three things happens — they're not the same. If the tab merely goes to the background or is minimized while staying open, on-screen updates pause (the display doesn't repaint while hidden), but the countdown keeps advancing against a monotonic timestamp, not a repeating tick — when you return, the remaining time normally recalculates correctly and the display catches straight up. The audible alert doesn't get the same free pass: the browser may suspend or throttle it enough that it plays late, only once you're back, or not at all. Device sleep or a locked screen is a different, less predictable case: neither that catch-up nor the alert firing at all is guaranteed there, since what actually happens to a paused browser tab across a real system sleep depends on the browser and operating system, not this page. Closing or reloading the tab or browser is different again, not just less reliable — nothing about this timer is saved, so the countdown itself is cancelled, not paused: there's no state left to catch up and no alert that can fire. For the best chance of hearing the alert, keep this tab open and active, keep the device awake, and ensure sound is allowed. Backgrounding the tab may delay or prevent the alert.