HIIT INTERVAL TIMER

High is work.
Low is rest.

Square Wave is a free, minimal interval timer for iOS. Set your work, rest, sets and rounds — then lock your phone, put your video back on, and just go with the beeps.

Square Wave setup screen: work, rest, sets, rounds and round break over a black Liquid Glass interface
Work interval running: azure gradient, glass dial counting down, round and total time remaining
Workout complete screen in gold with time, sets and rounds summary

Nothing between you and the next set

FEATURES
AUDIO

Beeps through anything

Cues mix on top of YouTube, Spotify or a podcast at full volume — no ducking, no interruptions. 3‑2‑1 ticks, one go‑tone, a halfway tick on long work intervals.

BACKGROUND

Locked‑screen reliable

The engine keeps perfect time with the screen off or another app in front. Date‑based math means no drift — even if iOS naps the app, it lands on the right second.

STRUCTURE

Sets, rounds, breaks

Work and rest per set, rounds of sets, and a longer break between rounds. Round‑remaining and total‑remaining, both at a glance.

DESIGN

Liquid Glass, properly

Built for iOS 26 with real glass materials over vivid phase gradients — azure work, violet rest, magenta breaks, gold finish.

PRICE

Free. Actually free.

No subscription, no paywall, no ads, no account, no analytics. Your timers live on your phone and nowhere else.

DETAILS

Sweat‑proof controls

Exit asks before ending (and pauses instantly, so a stray tap costs nothing). Skips are silent. Mute is one thumb away.

67%
DUTY CYCLE · 20s ⁄ 10s

An interval workout is a square wave — engineers call the work‑to‑rest ratio a duty cycle. Tabata classic runs 20s high, 10s low, eight cycles per round. The icon isn't decoration. It's the spec.