Slo vs Rain Rain: Which Sleep Sound App Fits? (2026)

Pick Rain Rain if you want a free phone app with 50 sounds, tone shaping on each one, a bedtime reminder and mixes that follow you between an iPhone and an iPad. Pick Slo if you want 11 rain tracks inside 200+ sounds, 89 of them free, and a timer that fades out after up to 24 hours.

The short answer

If you’re picking a rain app tonight, Rain Rain gives you more to play with on one phone for nothing, and Slo gives you more sounds and a way to hear them before you install anything. Rain Rain’s free tier holds 50 sounds, tone shaping on a single sound, a bedtime reminder and iCloud mixes across your iOS devices. Slo has 200+ sounds with 89 free, 11 of them rain, any number of layers at once, and 180 sounds you can play in this browser.

Rain Rain also carries a much larger public rating count, which matters if you like reading what people say after months of nightly use. On Slo’s side, there’s a Mac download, playback with no connection once a sound has downloaded in the app, and a timer that runs as long as 24 hours.

How we compared. Every Rain Rain fact below comes from its current App Store listing, its Google Play listing and its official site, all checked July 31, 2026. Neither app went through a controlled test. Slo is the app we build here, and its figures come from the app source, version 3.132, on September 14, 2026. Neither app can guarantee better sleep.

How Slo and Rain Rain compare

Where they differ	Slo	Rain Rain
Catalogue	200+ sounds in the app, 89 free; 180 free in the browser	Over 100 sounds; 50 of them free
Listen first	180 browser sounds, a mixer and 36 presets, no account	Install a phone app
Mixing	Any number of layers, a volume per layer, saved mixes	Mixer with Oscillator and Soften
Mix ceiling	No cap	Three sounds at once per Google Play
Sleep timer	15 minutes to 24 hours, fade-out up to 2 minutes	Every fade-out length in the free tier
Phones	iPhone and Android	iPhone, iPad, Android and Amazon
Desktop	Mac download	No Mac or Windows app listed
Public ratings	Not published here	4.8 across 136,160 App Store ratings
Money	Monthly, yearly or one-time lifetime	Free tier plus Premium subscription

You’ll notice no prices in that table. Store amounts move by country and by promotion, and the part that holds still is the model. Rain Rain runs a free tier next to a Premium subscription with a seven-day trial, and Slo sells a monthly or yearly subscription or a one-time lifetime purchase.

What you get with Slo

In the Slo app you get 200+ recorded sounds, with 89 of them free. Rain runs to 11 tracks and water to 9, alongside 22 noise recordings across seven colors, five of those brown. Stack as many layers as you like, give each one its own volume, and Slo keeps that balance for every combination you build. A mix you save exports as a file, and the file imports on another device. Set the sleep timer between 15 minutes and 24 hours, and the sound fades out over 15 seconds to 2 minutes before it stops. On an iPhone or an Android phone, playback keeps running as a background audio service with the controls on the lock screen. Each sound downloads the first time you play it in the app and stays there, so a saved mix plays with no network. The full library needs a monthly or yearly subscription or a one-time lifetime purchase, and 180 sounds play free at slonoise.com with no account.

Slo won’t shape the tone of a single sound or drift a volume up and down while it plays, and it can’t move a mix to a second device by itself. Rain Rain has Soften and Oscillator for the first two and iCloud sync for the third, while Slo asks you to export a file and open it on the other device.

What you get with Rain Rain

Rain Rain Sleep Sounds comes out of a one-person shop: Tim Gostony publishes it on the App Store and on Google Play, and the official site adds an Amazon route. Its Apple listing advertises over 100 endless sounds and puts 50+ of them in the free tier.

The free tier covers more than most apps in this category leave outside a subscription. Apple’s listing puts every fade-out timer length, the Mixer, the Oscillator, Soften, background audio, AirPlay and Bluetooth output in the free app. Oscillator moves a layer’s volume up and down at a speed you choose, so a loop keeps shifting while it plays. Soften trims the hiss off the top of a sound, which makes a downpour sit outside the window instead of running over your head. A small banner image sits at the bottom of the free app, and Apple’s listing says there are no audio or video ads.

Premium adds 60+ sounds and removes the banner. Apple’s page attaches a seven-day free trial to the subscription, and Google Play describes the same one-week trial. Custom mixes travel between a user’s iOS devices through iCloud, which Slo does not match today. A bedtime reminder nudges you at a time and on days you pick.

Where the two store listings disagree

The Apple and Android versions do not describe one identical product, so check the listing for the platform you own. Google Play caps a mix at three sounds at once; Apple’s listing sets no number. The Android listing shows a last update of July 25, 2024, while the iPhone version reached 6.9.10 on January 22, 2025. Apple’s release notes call a version 7 the biggest update yet and point to a public beta signup on Rain Rain’s site.

None of that makes the Android app broken. It does mean a 2024 build and a 2025 build can differ in ways no comparison table catches, and that older reviews may describe a version you cannot install.

The differences that matter

Browser listening

Slo plays in a browser, and that covers single sounds, the mixer and every preset. The Rain Rain site points you at the App Store, Google Play or Amazon, and we found no official web player during this check. If you’re on a work laptop that won’t let you install anything, that one fact settles the choice.

Sound counts, and what they hide

Slo’s 200+ sounds beat Rain Rain’s published total of over 100 on paper, and a count only tells you how big a catalogue is. The question that decides your night is narrower. Does the app hold the exact sound you already fall asleep to, looped long enough that you never catch it starting over? Rain Rain leans hard on rain and storms, with fans, a clothes dryer and a ticking clock beside them. Slo spreads its library across 22 noise recordings, 11 rain tracks, 9 water tracks and 9 instrument tracks. Our guide to noise colors explains what those color names describe.

Free catalogues split further apart than the totals suggest. Rain Rain keeps 50 of its sounds outside a subscription; all 180 sounds in Slo’s web player run in a browser tab at no cost, and 89 of the app’s 200+ stay free as well.

Mixing depth

Both apps layer sounds and give each layer its own volume. Rain Rain reaches further inside one sound, since Oscillator moves its level over time and Soften trims the hiss off the top, and both settings save with a favorite mix. Slo stacks as many layers as you want, remembers the balance for every combination you build, and ships 36 presets with the balance already set, which saves you the fiddling on a night when you want to press play once and go to bed. Neither app wins here, and it comes down to how much tinkering you enjoy.

Ratings, and how many people use it

Rain Rain carries 4.8 stars across 136,160 US App Store ratings, plus 4.7 stars across 11.3 thousand Google Play reviews on more than 500,000 Android installs. If you like to read a pile of reviews before you install anything, that’s a real advantage, because thousands of people there describe how the loops hold up over months of nightly use. Slo publishes no comparable rating count, and this page won’t invent one.

The bigger numbers need a caveat. Rain Rain’s site says over 10 million people have slept better with the app, while its App Store description says over eight million. Both figures sit in marketing copy, not in an audited report, so read them as claims the company makes about itself.

The claims to skip on both sides

Rain Rain’s Play listing describes its noise colors as calming the mind and reducing anxiety, its sound selection as a way to battle tinnitus, and good bedtime routines as reducing anxiety and improving sleep quality. Read that as store copy, not as a finding about the app. Research on continuous sound for sleep stays thin: a 2021 systematic review in Sleep Medicine Reviews rated the evidence very low quality with mixed results, and the World Health Organization’s noise guidance favors removing a noise over covering it when you have the option. Slo’s pages carry the same limits, which is why nothing on this page promises faster sleep, deeper sleep or relief for any condition. If poor sleep runs on for weeks, ask a clinician about CBT-I rather than shopping for another app. Our article on how sound affects sleep quality sets out the detail.

Which one should you choose?

Your priority	Better first test	Why
Listen before installing	Slo	Players, mixer and presets run on the site
A locked-down work laptop	Slo	Nothing to install
Mac playback	Slo	Rain Rain lists no Mac app
A timer longer than an evening	Slo	It runs to 24 hours and fades out before it stops
The largest free phone catalogue	Rain Rain	50 sounds free, no time limit
Tone control per sound	Rain Rain	Soften and Oscillator ship free
Mixes on an iPhone and an iPad	Rain Rain	iCloud sync between iOS devices
A long public review record	Rain Rain	Six figures of App Store ratings
Curated mixes with no setup	Slo	36 presets arrive pre-balanced
A bedtime nudge	Rain Rain	Bedtime reminder is a named feature

Whichever you pick, run the same test. Play one sound at the lowest level that covers the noise you actually hear, keep your alarm switched on, and compare a week of it against a week of quiet. Our walkthrough on sound mixing covers a sane starting balance, and the best sleep sound apps roundup lists other options if neither app fits.

Slo rain presets

Two ways to build a rain bed

The first mix stays near the surface of a rain loop. The second sits a rain layer over brown noise for a heavier base. Keep the quieter one.

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

Rain and Brown Noise for Deep Sleep

Brown noise covers the traffic and the boiler, and rain softens the sharper sounds inside the room.

• Brown Noise 65%
• Rain 38%

Play this mix View details

Frequently asked questions

Is the Rain Rain app free?

The download costs nothing on either store. Its listings put 50 sounds, the Mixer, Favorites, every fade-out timer length and the bedtime reminder in the free tier, with a small banner ad on screen. Rain Rain Premium adds 60+ sounds and takes the banner away, after a seven-day trial.

Does Rain Rain run in a browser or on a Mac?

On July 31, 2026 we found no official web player and no Mac listing. Rain Rain’s site sends you to the App Store, Google Play or Amazon. Slo plays 180 sounds, a mixer and 36 presets in any modern browser, and it lists a Mac download.

How many sounds can Rain Rain mix at once?

Google Play’s listing says three at the same time, and the Apple listing gives no number. Check the app on the platform you own, since the Android build last shipped in July 2024 and the iPhone build in January 2025.

Which app has more sounds?

Slo does, on the published counts, with 200+ against Rain Rain’s total of over 100. The free tiers differ more than the totals do, with 50 sounds free in Rain Rain against 89 free in the Slo app and 180 free in the Slo browser player.

Can I try Slo without installing anything?

Yes. All 180 sounds on the site run in a browser with no account, along with the mixer and the 36 presets. Press play on rain first, then open a mix such as rain on the roof, before you go anywhere near a store.

Official sources checked July 31, 2026

• Rain Rain, official iPhone and iPad App Store listing: over 100 sounds, 50+ free, Mixer, Oscillator, Soften, banner-ad note, iCloud mix sync, seven-day trial, version 6.9.10 of January 22, 2025, plus 4.8 stars across 136,160 ratings.
• Rain Rain, official Google Play listing: 50 free sounds, 60+ Premium sounds, the three-sound mix cap, fade-out timer, bedtime reminder, one-week trial, a July 25, 2024 update, 4.7 stars across 11.3K reviews, and 500,000+ installs.
• Rain Rain, official product site: App Store, Google Play and Amazon routes, the ad-free and no-time-limit claims, background playback, and the 10 million listener claim.
• Riedy et al., systematic review of white noise and sleep, Sleep Medicine Reviews, 2021.
• World Health Organization, environmental noise guidelines for the European Region, 2018.
• 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

• Slo vs Dark Noise
• Slo vs Noizio
• Best sleep sound apps
• Why white noise may help sleep
• Complete guide to noise colors

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