A Korean developer posted a bug fix at 2 a.m. on a mechanical keyboard forum, then built the best-selling "typing sound" keyboard on Korean iPhones

Thokey launched in Aug 27, and by Oct 31 it hit #8 on the Korea App Store Top Grossing Utilities chart. Several iPhone apps that play mechanical keyboard sounds have shown up this year, and only this one has taken off in Korea. The reason isn't the sound. It started as a Korean keyboard app people could use every day as their main input method, with the sound and cute themes layered on top. The dev first went through mechanical keyboard forums one thread at a time to find testers, then started paid acquisition on Instagram in October. A one-time purchase at 19,000 won, and plenty of people paid the moment they installed it.

A post at 3:27 AM

At 3:27 on 2026 Sep 16, a user named 「쏘키」 posted from a phone on DCinside, South Korea's biggest forum, in its mechanical keyboard mini-board. The title read 「형님들 기계식 키보드 앱 고쳤습니다」 (Guys, I fixed the mechanical keyboard app). The body was three lines: last time you all said typing lagged badly, so I did my best to fix it, and it feels much better now; I also added long-press to type double consonants.

Posts got 291 views and 6 replies. One person asked for a Samsung version ("갤럭시도 만들어주세요"), and he replied "여유가 되면 만들어보겠습니다" (if I have time, I'll make one). Another said the lag was so bad they kept mistyping ("반응이 너무 느려서 오타가 많이 납니다, 16 pro", using the 16 Pro), and he replied "아직도 버그가 있나봅니다 죄송합니다 ㅠㅠ" (guess there are still bugs, sorry ㅠㅠ).

379

That was the whole seed round. Later, App Store reviews still showed the same crowd: "쏘키형님 키갤러입니다" ("Brother Sogi, I'm from the keyboard gallery") and "개발하신 분이 디씨갤 하시는 분인가요?" ("Is the developer someone from the DC gallery?").

What it actually is

An iPhone custom keyboard. Once installed it replaces the system keyboard, and every keystroke plays real mechanical switch sounds.

• Sound: Red and Brown switches are free; Black, Blue, NovelKeys Cream, and Akko Lavender are paid. You can switch to "damping mode" for anything from a deep, muted "thock" to a crisp click, with adjustable vibration strength.
• Themes: Three free; paid ones include Liquid Glass, RGB Gaming, Strawberry Milk, Banana Milk, Matcha, and you can swap app icons. The Nov 3 1.7.8 update added a "Theme Workshop" where users can make their own themes.
• The real foundation is the keyboard: the first feature on the store page reads "Full support for Cheonjiin (Plus), Naratgeul, Vega, and single vowels" — all the common Korean keyboard layouts, plus split-screen and a number keypad.
• How it charges: Free to download. Paid tier is called "쏘키 Pass", with a subscription (7-day free trial), plus a one-time lifetime purchase at 19,000 won (about 14 US dollars).
• Pro

Why this one, and not other typing-sound apps

Between 7 and October, a handful of "mechanical keyboard sound" apps showed up on iOS. All were early or launched around the same time as Sokey, and none of them took off in Korea:

The difference in one sentence: apps that make sound can't be your main keyboard, and the ones that can be your main keyboard have no sound. Sokey covers both.

A keyboard is something you press hundreds of times a day. A toy sound app gets boring after two days and you switch back to the system keyboard. Sokey replaces the default input method, so the fun from the sound gets repeated hundreds of times a day. That's why people stay and why they're willing to pay. Lots of reviews say exactly this:

"So good I deleted the Naver keyboard. Saw Cheonjiin Plus and that was it."

"They even have the single-vowel layout? So moved."

"Just switched to iPhone Duo. The optimization is great, and split keyboard with a number pad? Totally get it. Bought lifetime right after one look." 11-03

Another reason that's easy to miss: the developer replies fast. A Nov 3 five-star review says "Never seen a developer give feedback this fast." Another from Nov 4 says "Sokey dev working like an ox." From September to Nov 3 the app shipped up to version 1.7.8. An input method is bound to have lag and compatibility issues. By Nov 4 someone reported on Instagram Stories that switching apps didn't work and dark mode wasn't applied. Fast bug fixes kept those bad reviews down.

Where users come from

The timing fits: September had only 18 reviews, October had 103. No sign of it on TikTok, X, or YouTube. No press coverage, and the developer hasn't shared revenue. Few people know about it yet.

Store search isn't the main channel: the app name includes "기계식 키보드" (mechanical keyboard). But searching "기계식 키보드 소리 아이폰 앱" (mechanical keyboard sound iPhone app) puts competitor Ttalkkak ahead (inferred).

How much it's making

No exact numbers are public. We can only estimate the range from the charts.

(App Store KR, daily)

The Korean Utilities top grossing chart's top 25 are mostly taken by NordVPN, Naver MYBOX, and VPN, cloud storage and old-app cleaner products. An app with only a couple hundred ratings and two months live charting at #8 shows one-time purchases are selling well here, and that the bar in this category isn't high. At this rank, daily revenue is likely in the hundreds-of-dollars range (est.). 19,000 A one-time purchase in won means each user is worth this much, with no renewals after that.

Over the past week both charts have been sliding (grossing 8→21, free 22→41). The first wave may be over, or ads may be eating into it. A review from October 30 says "다행히 10월이 지나기 전에 알게 되어 평생 이용을 결제" (luckily I found out before October ended, and paid for lifetime access). The lifetime price may have had a limited-time offer (unverified). In Japan, the app first showed up at #6 among free utility apps in November 203,5.

Its weak spots

• The lifetime purchase caps the ceiling. Impulse buys sell well, but each user is only worth $14, and revenue stops when the ads stop.
• iOS only. The first reply in the forum asked for a Samsung version. On Android, the global "Mechanical Keyboard: RGB Theme" already has 3.77M installs, but it has no Korean layouts.
• Input methods are hard work. The issues that keep coming up in reviews (volume drops after switching apps, some input fields won't switch, dark mode doesn't work) are longstanding iOS keyboard extension problems. They need constant fixing.
• Big companies could easily copy it. Adding typing sounds to the Naver keyboard isn't hard. Nobody has done it yet.

If it were you

Verdict: Worth a try. The combination of "a complete local-language input method plus emotional sound and themes" has been validated in Korea, and other languages are mostly empty. But the ceiling is a $14 purchase in a small-language market, and the input method itself is hard to build.

Who it's for: indie devs who are native speakers of a language, use their phone for it every day, and know which keyboard layouts locals use. Experience with iOS keyboard extensions is a plus. One person can build it.

Who it's not for: people hoping for big revenue; people who don't understand how the target language is typed and only want a global skin (SwitchKey and Quick Kibo didn't take off that way); people who can't stand fixing compatibility bugs all the time.

How to do it:

• Pick the language first. Criteria: locals have a few layouts they prefer, the system keyboard doesn't cover them, and no sound version exists locally. Look at Thai, Vietnamese, Traditional Chinese Zhuyin or Cangjie, Hindi, and similar. Japanese is already being built by Sokey, and kana-to-kanji conversion is much harder, so I wouldn't start there.
• The input method has to pass first: every common layout included, no dropped keys when typing fast, no sound cut-out when switching apps. This is the bar for people to delete their original keyboard. Sound and themes come later.
• Give away two switch sounds and a few plain themes for free. Put the paywall on the better switches and nicer themes. Sell both a subscription and a lifetime purchase at the price of a couple of coffees.
• Android is the part Thokey hasn't built. In Korea, an Android Korean mechanical-keyboard app is an open gap, but you have to beat Thokey to it before they build it themselves.

How to get users: Start in local mechanical-keyboard communities (forums, Discord, Facebook groups). Post under a real handle, collect feedback in public, and fix things the same day; these people will write your first batch of reviews. Once reviews stop complaining about lag, run Instagram and Threads ads of real mechanical keyboard typing ASMR, with the pitch that phone typing sounds like a real keyboard.

When to move: Typing-sound apps of this kind only started piling up in the second half of this year. Shipping a single language within six months is a safe bet; wait much longer and a generic sound keyboard may add local layouts.

Signs that would mean you read it wrong:

1. Sokey fell out of the Korea Store's Utilities Top Grossing top 50 a few months in, and new ratings dropped to single digits a day. It was mostly carried by one ad push and the lifetime-purchase impulse, with no retention behind it. Switching languages won't fix that.
2. Thokey's Japan store took off within six months, so the playbook can be copied across languages. But Japan has stayed flat, which suggests the Korea market is special: a big mechanical-keyboard scene, and Koreans used to paying for input methods. Other languages need more caution.
3. If Naver Keyboard or Samsung Keyboard adds typing sounds, the local input-method giants will pick up this feature easily, and the indie-dev opening disappears.
4. Someone has tried the same combination in other languages and couldn't sell for months. That suggests Thokey's success came mostly from Korea's mechanical-keyboard subculture, not from the combination itself.