Box breathing uses four equal phases — breathe in for four seconds, hold for four, breathe out for four and hold for four — which makes it easy to learn and good for steady focus and calm. The 4-7-8 pattern, popularised as a relaxing breath, inhales through the nose for four seconds, holds for seven and exhales through the mouth for eight; the long exhale and breath-hold are meant to settle the nervous system before sleep. Both involve holding the breath, so breathe gently and stop if you feel lightheaded. AnyTool animates either pattern with an expanding and contracting circle so you can follow the rhythm without counting.

In meditation timer mode you choose the session length and, optionally, an interval bell — for example every 3, 5 or 10 minutes. A gentle chime then rings at each interval so you can gauge your progress with your eyes closed, while a start bell opens the session and an end bell closes it. You can also add a silent warm-up before the first bell. Each chime is synthesised with the Web Audio API as a warm bell tone, so there is no audio file to download, and the timer is timestamp-based so the bells stay on schedule even if the tab is briefly throttled. Keep the tab open and your device awake for them to ring.

Coherent or resonant breathing means breathing slowly and evenly at around five to six breaths a minute, with the inhale and exhale roughly equal — AnyTool uses about 5.5 seconds in and 5.5 seconds out. This rate is associated with the body’s resonance frequency, where heart rate, blood pressure and breathing synchronise and heart-rate variability is highest, which is why it is used for relaxation and stress relief. There are no breath-holds, so many people find it the gentlest pattern. The breathing guide paces it for you with a circle that simply grows as you breathe in and shrinks as you breathe out.

The timer is completely free with no account, and all timing, the bells and the breathing cues run client-side in your browser, so nothing is ever sent to a server and it works offline after first load. It is a tool for relaxation and mindfulness, not a medical device or a substitute for professional care. Breathing exercises — especially patterns with breath-holding like Box and 4-7-8 — can cause some people to feel lightheaded; breathe gently, never strain, and stop if you feel faint or short of breath. If you are pregnant, have a heart or lung condition, or have been advised against breath-holding, check with your doctor first, and never practise while driving.