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

Choose Slo if you want to hear rain in the browser before visiting an app store, or you need a Mac download; choose Rain Rain if you want 50 free phone sounds with Soften tone shaping, Oscillator volume drift and mixes that follow you between iPhone and iPad.

Disclosure: Slo’s team publishes this comparison. Rain Rain facts come out of its current App Store listing, Google Play listing and official site, all checked July 31, 2026. We have not run a controlled test of either app, and neither half of this page promises better sleep.

The short verdict

Choose Slo if you want to hear a sound in your browser before installing anything, and if a curated library of 151 sounds with ready-made mixes suits the way you work. Choose Rain Rain if you want a phone app with 50 free sounds, per-sound tone shaping, a bedtime reminder and mixes that follow you between an iPhone and an iPad.

The split is simple. The deeper toolkit on a single device belongs to Rain Rain, along with a far larger public rating base. Slo has browser playback, a Mac download path and a wider catalogue you can audition without a store visit.

How Slo and Rain Rain compare

Where they differ	Slo	Rain Rain
Catalogue	151 curated sounds	Over 100 sounds; 50 of them free
Listen first	Browser players, mixer and presets	Install a phone app
Mixing	Adjustable layers plus curated presets	Mixer with Oscillator and Soften
Mix ceiling	Layered browser presets	Three sounds at once per Google Play
Sleep timer	Timer in the browser players	Every fade-out length in the free tier
Phones	iOS and Android download paths	iPhone, iPad, Android and Amazon
Desktop	Mac download path	No Mac or Windows app listed
Public ratings	Not published here	4.8 across 136,160 App Store ratings
Money	Check current store terms	Free tier plus Premium subscription

Prices stay out of that table on purpose. Store amounts move by country and by promotion, so the durable difference is the model: Rain Rain runs a free tier alongside a Premium subscription with a seven-day trial, while Slo’s app terms belong to whichever store page you open.

What you get with Slo

Slo’s current product source lists 151 curated sounds for sleep, focus and relaxation. The website carries single-sound players with volume and timer controls, a multi-layer mixer and curated presets such as Deep Work Studio. You can test brown noise, rain, a river or a fireplace in a browser tab, then decide if an app belongs on your phone at all.

Slo also lists download paths for iOS, Android and Mac. This page claims no offline playback, no account sync and no identical feature set across those three platforms, because Slo’s own fact ledger does not cover them. Treat the browser as the part you can check in thirty seconds, and the apps as the part you check in your own store.

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 feature set is unusually generous for this category. Apple’s listing names every fade-out timer length, the Mixer, the Oscillator, Soften, background audio, AirPlay and Bluetooth output, all without a subscription. Oscillator drifts a layer’s volume up and down at a speed you set, which keeps a loop moving instead of sitting flat. Soften rolls off high frequencies so a downpour sounds like weather outside the window rather than a shower over your head. A small banner image sits at the bottom of the free app; 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: 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. On a work laptop you cannot install software on, that one fact settles the choice.

Sound counts, and what they hide

Slo’s 151 sounds beat Rain Rain’s published total of over 100 on paper. Counts measure catalogue size and nothing else. The useful question is narrower: does the app hold the exact texture you already fall asleep to, looped at a length that never draws attention? The Rain Rain catalogue leans hard on rain and storms, with fans, a clothes dryer and a ticking clock alongside them. Slo spreads its library across noise colors, weather, water and quiet instruments. Our guide to noise colors explains what those color names actually describe.

Free catalogues split further apart than the totals suggest. Rain Rain keeps 50 of its sounds outside a subscription; all 144 sounds in Slo’s web player run in a browser tab at no cost.

Mixing depth

Both apps layer sounds and give each layer its own volume. The Rain Rain app reaches further inside a single sound: Oscillator varies its level over time, Soften trims the top end, and both settings save with a favorite mix. Slo exposes each layer in the browser and ships presets that already set a sensible balance, which spares you the fiddling if you would rather press play once and get on with your evening. Neither approach wins outright, and the choice comes down to how much tinkering you enjoy.

Reviews and reach

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. For a cautious buyer that volume of feedback counts as evidence of a different kind: thousands of people describe how the loops hold up over months of nightly use. Slo publishes no comparable rating count, and this page will not invent one.

One caveat on reach. 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 live in marketing copy rather than an audited report, so read either as a claim instead of a measurement.

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
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	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 depths of rain gather above a quiet room, steadied by a neutral grey hush.

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

Play this mix View details

Rain and Brown Noise for Deep Sleep

A low, steady foundation softened by the natural detail of rainfall.

• Brown Noise 65%
• Rain 38%

Play this mix View details

Frequently asked questions

Is Rain Rain free?

The download costs nothing on both stores. 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. Rain Rain Premium adds 60+ sounds and removes the banner after a seven-day trial.

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

We found no official web player and no Mac listing on July 31, 2026. Rain Rain’s site points to the App Store, Google Play and Amazon. Slo runs its players, mixer and 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 up to three at the same time. The Apple listing gives no cap. Check the app on your own platform, since the Android build last shipped in July 2024 and the iPhone build in January 2025.

Which app has more sounds?

Slo, on published counts: 151 against Rain Rain’s total of over 100. Only 50 of Rain Rain’s sounds sit in the free tier, so the gap widens once you compare what costs nothing.

Can I try Slo without installing anything?

Yes. The players, mixer and presets run on the website. Start with rain, then open a full mix such as rain on the roof before you visit any 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, live browser players, mixer, presets and current product source, checked July 31, 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.