Free browser tool
Contrast therapy timer
Warm, cold and the change-over, timed independently. No account, and nothing leaves your browser.
Warm
3:00
Round 1 of 3 · 13:40 total
Keyboard: Space start or pause · S skip · R reset
Sauna, hot bath or hot shower · 3:00
Plunge, ice bath or cold shower · 1:00
Time to move between the two · 0:20
One warm and one cold each
Starts on warm
Changing any setting resets the session. Nothing here is stored or sent; reloading the page returns the defaults.
This is a timer, not a medical device. It counts seconds; it doesn't know anything about you, and it can't tell whether a session is safe. Alternating heat and cold is real cardiovascular stress — get out for dizziness, chest discomfort, nausea or shivering that won't stop, never do it alone in water deep enough to drown in, and never after drinking. See the safety guide.
How to use it
- 1. Set the two durations. Warm and cold are independent, because they are not the same length in any real protocol. Sports-science contrast protocols run close to 1:1; a sauna cycle is heat-dominant, often 10 to 15 minutes hot to 1 to 3 minutes cold.
- 2. Set the change-over. The walk between sauna and tub is real time. Counting it separately is what keeps the rest of the session honest instead of quietly stretching every warm phase.
- 3. Pick rounds and which phase you start on. Starting warm makes the first cold entry easier. Starting cold is the harder version.
- 4. Press start and put the screen down. A cue sounds on every phase change, so you don't need to watch it. Space pauses, S skips the current phase, R resets.
If you want the reasoning behind the numbers — and which of the usual claims about contrast therapy the evidence does not support — read the contrast therapy guide.
What a browser tab can't do
This page is genuinely free and has no catch — but it is a browser tab at the side of a cold tub, and there are four things it will never do well.
- It forgets. Nothing is saved. Close the tab and the session is gone, along with any record that you did it.
- It has no haptics. A phone can beep. A watch taps your wrist, which is what you want when your eyes are shut and your ears are underwater.
- It needs your phone nearby and awake. Wake lock helps where it's supported, but the device still has to be out, unlocked and dry.
- It can't tell you whether you're progressing. That needs a history: the same protocol, the water temperature, over months.
Those four are exactly what the app does: saved rituals and up to 20 rounds, haptic phase changes, a standalone Apple Watch app that leaves the phone indoors, and a session history that stays in your own iCloud. Use this page as long as it's useful — it isn't crippled to push you anywhere.
Questions
Is this contrast timer free?
Yes, completely. It runs in your browser, needs no account, and nothing you enter is sent anywhere — there is no server to send it to. Set your durations and press start.
What durations should I use?
It opens on 3 minutes warm, 1 minute cold, 3 rounds, with a 20-second change-over, which is a reasonable place to start. Contrast water therapy in sports research usually uses a roughly 1:1 ratio for 6 to 15 minutes total; the Nordic sauna cycle is far more heat-dominant, around 10 to 15 minutes hot to 1 to 3 minutes cold. The contrast therapy guide explains where those numbers come from and how much confidence they deserve.
Will the screen stay on?
On browsers that support the Screen Wake Lock API, the timer asks to keep the screen awake while it runs and releases it when you stop. Where that isn't supported, the screen may dim — which is one practical reason a watch app beats a browser tab at the side of a cold tub.
Does it work offline?
Once the page has loaded it keeps running without a connection, and the site is a PWA, so a previously visited page is cached. It is still a browser tab: closing it loses the session.
Does it save my sessions?
No. This tool deliberately stores nothing — no history, no account, no cookies for it. If you want the session recorded with its temperature, rounds and notes, and a history you can look back at, that's what the TrackCold iPhone and Apple Watch app is for.
Want the session to count?
TrackCold runs the same rounds from your wrist, taps you through each phase change, and keeps the history. Free to download; no account either way.
More on TrackCold: Cold plunge timer · Ice bath timer · Cold plunge tracker · Apple Watch app