Noizio vs Slo: Browser Sound Mixer, No Download

Pick Noizio if you’d rather pay once for a compact set of 40+ sounds and have your mixes follow you between an iPhone and a Mac. Pick Slo if you want a bigger library, 200+ sounds with 89 of them free, and 180 you can hear in a browser before you install anything.

The short answer

You’re weighing a small app you buy once against a larger library you can try for nothing first. Slo fits if you want 200+ sounds with 89 free, a mixer with no cap on layers, a timer you can stretch to 24 hours, and a way to listen before you download. Noizio fits if its 40+ sounds cover what you need, you prefer a single unlock to a subscription, and you want the iCloud mix sync its Apple version history describes.

One thing to know before you buy Noizio. Its iOS listing, its separate Mac listing, its current Android listing and an older Android listing don’t all describe the same app, so check the features on the store page for the device in your hand.

How we compared. The Noizio facts here come from its current App Store, Google Play and privacy-policy pages, checked July 31, 2026. Those listings have different histories, so where they disagree this page says so and leaves the question open. Slo is ours, so its figures come straight from the app source, version 3.132, on September 14, 2026. Neither app can guarantee better sleep or focus.

Slo vs Noizio at a glance

Decision	Slo	Noizio
Verified sound count	200+ in the app, 89 free; 180 free in the browser	40+ on current iOS and Android listings
Main workflow	Any number of layers, a volume per layer, saved mixes	Choose sounds, set each volume, save mixes
Browser path	180 sounds, a mixer and 36 presets, no account	No official web player found
iPhone/iPad	Download path available	Current App Store listing
Android	Download path available	New 2026 listing plus a separate legacy listing
Mac	Download path available	Separate Mac listing; iOS listing also reports Apple-silicon Mac compatibility
Sleep timer	15 minutes to 24 hours, fade-out up to 2 minutes	Auto-pause timer; Android listing adds a fade-out timer
Offline claim	Yes, after download	Stated by Noizio’s current listings
Payment model	Monthly, yearly or one-time lifetime	Store pages describe a one-time full-library unlock

There are no amounts in that table, because they shift with your platform, your country and your store. What you can plan around is the model. Noizio describes one unlock that covers the library, while Slo sells a monthly or yearly subscription or a one-time lifetime purchase.

What Slo offers

The Slo app carries 200+ recorded sounds, with 89 of them free to anyone. Among them are 22 noise recordings across seven colors, five of those brown, plus 11 rain tracks and 9 water tracks. Add as many layers as you want, set a volume on each one, and Slo keeps the balance for every combination you build. Any mix you save exports as a file, and that file imports on another device. The sleep timer covers everything from 15 minutes to 24 hours, then fades the sound out over 15 seconds to 2 minutes before it stops. On iPhone and Android, playback runs as a background audio service and the lock screen keeps the controls. In the app, a sound downloads the first time you play it and stays on the phone, so a saved mix runs with no network. The full library sits behind a monthly or yearly subscription or a one-time lifetime purchase, while 180 sounds play free on slonoise.com without an account.

Slo has no alarm clock, and it can’t send a mix to a second device by itself. Noizio’s listings describe sync between an iPhone and a Mac, while Slo asks you to export a file and import it on the other machine.

What Noizio offers

Noizio’s current iPhone and iPad listing describes 40+ ambient sounds, a volume per sound, loops that repeat without a seam, background audio, an auto-pause timer, offline playback, and a store where you can add more sounds. Its version history documents mix synchronization between iOS and macOS. The separate Mac product lists mixing, offline playback, an auto-pause timer and alarm, hotkeys, and better synchronization with iOS.

Android needs more care. Google Play currently shows two of them:

• a redesigned package updated June 16, 2026, with 40+ sounds, saved mixes, a fade-out timer, offline playback, and a one-time library unlock; and
• a legacy package last updated in 2020, with five included sounds and an older feature set.

Between those two pages, “Noizio on Android” covers more than one app, so check the package name and the update date before you buy or compare features. Noizio’s current privacy page says one in-app purchase unlocks all the sounds, and the exact terms still depend on the store you buy from.

The differences that matter

Browser use

Slo’s players, mixes and presets all run in a browser tab. We looked for an official Noizio web player and didn’t find one. On a work computer where you can’t install software, or when you just want to hear a sound before committing to it, that’s the most useful difference on this page.

Library size and selection

Slo has 200+ recorded sounds with 89 of them free, and current Noizio listings say 40+. Noizio’s set spans noise colors, weather, nature, urban scenes and tonal wave tracks, and Slo draws from a larger pool. Since a count tells you nothing about how a recording sounds, go look for the specific sound you plan to sleep or work to.

Apple sync and Mac packaging

Noizio’s App Store history records mix sync between iOS and macOS. Slo doesn’t sync at all, so a mix moves as a file you export and import. Noizio also has its own Mac listing while its iOS listing says the app runs on newer Apple-silicon Macs, and those two routes may not carry the same purchase or the same behavior. Read the listing you’re about to install.

Android ambiguity

Slo has one current Android download, linked from its website. Noizio has the redesigned Android listing and the old one side by side. The new package looks heavily updated, but with both pages live, a review or a feature list you find online may belong to the app you didn’t install.

Offline playback and payment

Noizio states offline playback and a one-time unlock on its pages. In the Slo app, each sound downloads the first time you play it and stays on the device, so a saved mix keeps running with no network, and the full library costs a monthly or yearly subscription or a one-time lifetime purchase. If one of those points decides it for you, confirm it on your own device and store page.

Which one should you choose?

Your priority	Better first test	Why
Mix in a browser	Slo	180 sounds, a mixer and 36 presets, no account
More verified sound choices	Slo	200+ in the app, 89 of them free, against Noizio’s 40+
One-time full-library unlock	Noizio	Its current pages describe that model
Offline playback	Either	Noizio’s listings state it, and Slo’s app keeps each sound after the first play
iOS–Mac mix synchronization	Noizio	Its Apple version history documents it
Android without package ambiguity	Slo	Noizio has a current and a legacy Android listing

Whichever you try, keep the volume low and judge it in the room you actually sleep or work in. A bigger catalogue and a synced mix don’t make a night better on their own. Our page on how to use sound mixing sets out a starting balance.

Slo presets

Compare a natural loop with a deeper work mix

Rain on a Roof is the simpler scene, and Deep Work Studio sits on a steadier noise base. Keep whichever one you stop noticing after a few minutes.

Rain on the Roof

Two kinds of rain at once, close drops and a wider shower, with a quiet hush holding them together.

• Ambient Rain 50%
• Gentle Rain 34%
• Grey Noise 20%

Play this mix View details

Deep Work Studio

A steady rumble, a wide ambient sound, and typing quiet enough that you barely catch it.

• Brown Noise 48%
• Deep Focus 32%
• Keyboard Typing 9%

Play this mix View details

Frequently asked questions

Is the Noizio app on Android in 2026?

Yes, though Google Play still shows two of them. One is a redesigned app updated in June 2026, and the other is a legacy app last updated in 2020. Check the package name and the update date before you trust an old review or feature list.

Does Noizio work on Mac?

Yes. It has its own Mac App Store listing, and the iOS listing also reports that the app runs on qualifying Apple-silicon Macs. What you buy and what you get can differ between those two routes.

Does Noizio sync mixes between iPhone and Mac?

Its App Store version history says iCloud mix synchronization between iOS and macOS was added. Nobody here has tested how that behaves today, so treat it as the listing’s claim.

Can I use Slo or Noizio in a browser?

In a browser, Slo gives you 180 sounds, a mixer and 36 presets, and it asks for no account. We looked for an official Noizio web player during the July 2026 audit and didn’t find one.

Which has more sounds?

Slo has 200+ recorded sounds in the app, 89 of them free, and 180 free in the browser. Noizio’s current iOS and redesigned Android listings say 40+. What settles it is whether the sound you already sleep to is in there.

Official sources checked July 31, 2026

• Noizio, current iPhone/iPad App Store listing — 40+ sounds, mixing, timer, offline playback, Mac compatibility, and version history.
• Noizio, separate Mac App Store listing — Mac-specific controls, timer/alarm, offline playback, and iOS synchronization notes.
• Noizio, current Android listing — June 2026 redesign, 40+ sounds, saved mixes, timer, offline use, and unlock model.
• Noizio, legacy Android listing — separate package and 2020 update history.
• Noizio, official privacy policy — current ownership/privacy statement and one-time unlock description.
• Slo app source, version 3.132 (sound list, timer, fade-out and store products), and the slonoise.com sound catalogue, reviewed September 14, 2026.

Related comparisons and guides

• Best sound mixing apps
• Slo vs Dark Noise
• Brown, white, and pink noise compared
• How to create a sleep soundscape

Filip Kowalski is the developer of Slo and writes about sound, sleep, and focus.