White noise is random sound with equal energy at every frequency, which makes it sound like a steady hiss: television static, an untuned FM radio, or air escaping a valve. It is the flattest possible spectrum and the reference from which every other noise color is derived. Used at low volume, it masks unpredictable sounds so that they are less likely to break your concentration or wake you up.
This page is a white noise machine that runs in your browser. It is free, open source, and free of ads, accounts and tracking. Unlike apps that loop an audio file, the noise here is synthesized continuously by the Web Audio API and never repeats. There is a sleep timer, a WAV exporter, and you can install it as an app for offline use.
Free, no ads, no signup. Runs entirely in your browser.
Pure white noise is bright. Think of the sound between stations on an analog radio, a cassette deck with the tape stopped and the volume up, or a detuned CRT television. There is bass in it, but the ear does not notice, because each higher octave contains twice as many individual frequencies as the one below it and so carries twice the energy. Most of what you hear is above 2 kHz.
That brightness is what makes white noise so effective at covering high-pitched interruptions, such as clicking keyboards, voices in the next room, or a ringing in the ears. It is also what makes some people find it harsh over long sessions, which is why this site offers pink, brown and grey variants alongside it.
The defining property of white noise is a flat power spectral density: the same power in each hertz of bandwidth, whether you look at 50 Hz or 15 kHz. On a linear-frequency analyzer it draws a horizontal line. On a logarithmic analyzer, the kind that shows octaves as equal widths, it rises 3 dB per octave, because each octave is twice as wide as the previous one and gathers twice as much power.
It is called white by analogy with white light, which contains all visible wavelengths. Every colored noise on this site is a filtered version of white: pink and brown roll the highs off, blue and violet roll the lows off, and grey reshapes it to match how loud the ear perceives each band. The mathematics is laid out on the physics page.
White noise is the simplest signal to synthesize: every sample is an independent random number. The default distribution here is Gaussian, produced by transforming uniform random values, which gives the smoothest and most natural-sounding hiss. A uniform option is also available under the texture control; it has the same flat spectrum but a slightly grainier character that some people prefer for mechanical sounds.
Because the samples are generated in an audio worklet as the sound plays, the output is truly non-repeating. A sound machine or an app that plays a recorded file has to loop it, usually every thirty seconds to a few minutes, and the loop point is often audible once you know to listen for it. There is nothing to loop here.
Masking works by raising the floor. A quiet room lets every small sound stand out; a room with a steady background makes the same sounds a smaller fraction of what you are hearing, so they draw less attention and are less likely to wake you. White noise is a good general-purpose masker because it covers the whole range. It is commonly used in open offices, nurseries, shared apartments, hotel rooms, and by people with tinnitus.
The trade-off is that pure white noise has more treble than most people want for sleep. If you are choosing a color for overnight use, the sleep page covers the options. If you are trying to cover a specific pitch, such as tinnitus, the tinnitus masking page explains how to match it.
Everything a hardware white noise machine does is available here without buying anything. Press play to start Pure White. The sleep timer fades the sound out at the time you choose. The volume keys and the space bar work as shortcuts. Install it as an app from your browser's menu and it will open full-screen and play offline, on Android, iOS, Windows, macOS and Linux, in Chrome, Firefox, Safari or Edge.
If you want a file for a device that cannot run a browser, the export button writes a WAV of any duration you choose. A shareable URL carries your exact settings, so you can bookmark a favorite or send it to someone else. There is no account to create and nothing is stored on a server; custom presets you save live in your own browser.
In most respects it is better. Hardware machines either loop a recording or use a small fan; this generator synthesizes new noise continuously, so there is no loop seam. Sound quality depends on your speaker or headphones. The one advantage of a dedicated machine is that it cannot be interrupted by a notification or a phone call.
Not at reasonable volume. Any sound played loudly for a long time can damage hearing, and white noise is no exception, but at the low level needed for masking it is well below the danger threshold. Keep it quiet enough that a normal conversation is still easy. Be especially careful with earbuds, which sit close to the eardrum.
Pediatric guidance commonly suggests keeping it under about 50 dB at the infant's ear, roughly the level of a quiet conversation, and placing the source across the room rather than next to the crib. Many parents find pink or brown noise gentler than white for this purpose. Ask your pediatrician if you are unsure.
Because of how hearing works. White noise has equal energy per hertz, but each octave contains twice as many hertz as the one below it, so the ear hears a spectrum that rises 3 dB per octave. Most of the perceived loudness is in the treble. Pink noise corrects for this and sounds balanced; brown noise goes further and sounds deep.
Usually. Most current mobile browsers keep audio playing when the screen locks, and installing the site as an app makes this more reliable. Some browsers pause background audio to save power; if yours does, try installing the app or, as a fallback, export a WAV and play it from your music app.
Many people find that it does, mostly because it masks the sudden sounds that would otherwise wake them. Controlled studies are small and their results are mixed, so there is no strong evidence either way for the average sleeper. It is harmless to try at low volume, and pink or brown are worth comparing if pure white feels too bright.