One zip, the phone unlocks: how a small Hanoi studio bought 1.57M installs in three months on an old lock-screen gimmick

A phone lock screen app: swipe down and the screen splits open like a zipper, and the phone unlocks. This mechanic has been on Google Play for years, and the top one has 34M installs. A small studio in Hanoi only shipped its version in July, with nothing new in the product, yet by Nov 6 it had 1.57M cumulative installs and 7k new installs in 140 days. Below: what it's riding on, where the money comes from, and whether this path is still open to you.

Aug 15, the curve turned a right angle

Zipper Lock Screen Customizer launched in July 16 (2026 year). For its first month it was quiet, around 1,000 installs a day, and by Aug 14 it had 41k in total (third-party daily install estimates; same below).

Starting Aug 15, the numbers suddenly jumped to about 28k a day, more than 20x in three days. They never dropped back: early September hit 420k, early October 1.04M, and in Nov it was 6 on Google Play 1,569,263.

This shape, flat for a month then a right-angle jump and a stable high plateau, is rarely a video going viral by chance. It almost always looks like money going into ads. In Aug 27 a user's review became one of the most-liked (127 people found it helpful):

really nice but lots of ads though me personally I don't mind

Paid ads pull people in, and ads plus paid themes inside the app earn the money back. This app is entirely built on that loop.

What it is

Open the app and pick a wallpaper first: football stars, anime, plush, royal, neon, starry sky. The store page claims 1,000+ HD images. Then choose the zipper pull's look, glow color, tooth layout, and whether to enable the "zip" sound effect. Once set, the lock screen shows a zipper, and dragging your finger down unlocks.

The store page's first line is "Make your phone your personality", the second "Goodbye boring, plain lock screen". The name "Customizer" is its only claimed difference: most rivals let you pick ready-made themes, while this one lets you design the zipper yourself. Honestly, it feels about the same in use.

The developer listed on the store is Midas Studio App, backed by MEDICI TECHNOLOGY JOINT STOCK COMPANY, address floors 3-4, 1 Thai Ha Street, Hanoi (Google Play developer info, 11-06). Since November 2025 the studio has rolled out a string of similar apps: car wallpapers, 4K live wallpapers, AI car editing, ringtones, anime wallpapers. The latest, AI car editing, launched in Oct 27 and hit 47k installs in 10 days. Its site lists "ASO & growth" as one of four steps and is hiring remote User Acquisition staff.

Zipper lock screens are only possible on Android. iOS doesn't let third-party apps change the unlock animation, so the equivalent there is limited to static wallpapers.

A category that's already crowded

To be clear: this isn't a new idea. On Google Play there are more than a dozen zipper lock apps by name, mostly from small studios in Vietnam, India and the Middle East, and their package names look alike.

(Google Play installs, 11-06)

By size it ranks eighth, and by this week's new installs third, behind Sky Technology Labs and MGlobal. Other zipper lock screen apps also launched in the same month, in June and July.

Users don't need educating. On TikTok, the Vietnamese account @wallpaper_lockscreen_zip posted "Fresh your lock screen! Download now!" in July 2025 with 27.9M views. Another Vietnamese account, @xyreviewngon_20, has several zipper lock videos from 2024, each with 3.6M to 4.6M views. Their titles all say "Download", which reads like ad creative. Young users in South Africa, Nigeria, Brazil and Southeast Asia already know that a lock screen can be a zipper.

How it bought users

Ad buying, confirmed. The app ships with AppsFlyer, a tool for tracking which ad each user came from; an app that isn't buying traffic has no use for it. It also integrates AdMob mediation and 11 ad networks including Google, Facebook, AppLovin and Unity (per AppGoblin SDK scan). A Facebook page with the same name posted a video in Sep 28: "Make your screen pop with 100,000+ 4K zipper lock styles, free in one tap", with 4,300 views and 11 reactions. Such low engagement paired with copy this much like a product pitch basically means an ad creative parked on the page. Which channels it ran on and how much it spent is not visible from outside.

Changed category, confirmed; whether it was deliberate is inference. Its peers almost all sit in Personalization, which is packed with wallpapers, themes and icon packs. This one sits in Art & Design, a much smaller category where you don't need many installs to reach the top. In Nov 6 it ranked in the Art & Design Top Free chart in 28 countries: #9 in South Africa, #22 in Brazil, #25 in Nigeria, and also top 35 in Thailand, Saudi Arabia, Vietnam, Turkey and Indonesia; it sat around #30 to #40 in Germany, Poland, Sweden and Italy. It never entered any overall chart or the Top Grossing chart. Bought installs pushed it onto the category chart, and the category chart brought in some free exposure on top. The same studio's AI car editing and anime wallpapers are also in Art & Design, so it's likely intentional.

Cheap countries. The best-ranking countries, South Africa, Brazil, Nigeria, Saudi Arabia and Southeast Asia, are markets where an install costs a few cents to around ten cents (estimate). The wallpapers feature football stars and anime, matching the tastes of young people there; reviews even ask for Messi by name.

Store search. The package name free.ziplocker.zipperlockscreen.wallpaper stuffs zipper, lock, screen and wallpaper all in.

Nudged ratings, inferred. The South Africa reviews include a big batch of one-or-two-word five-star ratings: "❤️", "pet", "it's so cute", and one that reads "zipper lock Rate this app", which looks like a tap-through on the in-app rating prompt. The store page shows 4.5 stars from 8,760 ratings (11-06), noticeably higher than the complaints in the review section suggest.

Where the money comes from

Two-sided income: ads inside the app, plus in-app purchases at $1.99 to $14.99 each (listed on the store page). The negative reviews name exactly these two things: too many ads, paywalls popping up without warning, and having to stay online. The most-liked negative review was just one line: "The app is great, the problem is the ads".

The third-party data site AppGoblin estimates about 307k monthly actives and over $50k monthly revenue, 70% from in-app purchases and 30% from ads. This is a model estimate and can't be verified. Working backwards from the 140k weekly new installs, if each install costs roughly ten cents, monthly spending would be tens of thousands of dollars (estimate). Set against that revenue estimate, it's a thin-margin, volume-driven business. The real payback is not visible from outside.

How it differs from peers

On the product there's almost no difference. Picking wallpapers, zipper pulls, glow, sound effects and previews are all standard across the top apps. What's genuinely different is distribution: it was placed in a smaller category, paid acquisition concentrated in cheap countries, and the studio already had a ready-made pipeline for buying traffic and monetizing, which it had already run on car wallpapers and live wallpapers.

So "why is it hot" isn't about the product, it's about the playbook. No media has written about it, nobody on X talks about it, the founders never flaunted their revenue, and the only pages you can find are auto-generated ones from a few data sites. Few people outside know this App exists; dozens of studios doing this category already know everything there is to know.

If it were you

Verdict: Copying the zipper lock screen isn't worth it. What's worth learning is the playbook: take an old category, list it under a smaller sub-category, buy installs in cheap countries, monetize with both ads and in-app purchases, and have one studio ship a new app every few weeks.

Who it suits: Studios already making Android tools / wallpapers, with paid-acquisition experience, a few tens of thousands of dollars in working capital, and tolerance for an app that only lives a few months. For you it's a template you can copy: pick a "fun lock screen / wallpaper" mechanic nobody has beaten to death yet, and run the same process.

Who it doesn't suit: Indie devs who can't run ads and are counting on organic traffic (this category has piles of look-alikes sitting in the store with no downloads); iOS developers (the system won't let you change the unlock animation); anyone trying to build a long-retention, word-of-mouth product (users install it for novelty and uninstall within days).

How to do it:

• Stop crowding into zipper lock screens. Go find the next "small trick you can do on the lock screen" or a similar visual mechanic. Search TikTok first, and look for ones with single videos hitting hundreds of thousands or millions of views that a dozen-plus studios haven't turned into apps yet.
• Before you publish, check the category charts: the same kind of app placed under Personalization vs. Art & Design, Entertainment, or Lifestyle each needs a different number of installs to reach the top #20. Pick whichever has the lowest bar.
• Don't cram ads as densely as it does, and state the paywall up front. Nearly all its bad reviews are about these two things. Cutting back on annoying users should improve ratings and retention (my inference).

How to acquire users: Test first in cheap, English-speaking countries like South Africa, Nigeria, and the Philippines. Run 15-second "swipe to unlock" vertical videos on Meta, AppLovin, and Unity. At the same time, run several TikTok alt accounts posting the same videos; competitors are already doing this. Swap the creative by country; football and anime work best.

Timing: The lifespan of this kind of mechanic is measured in months. The zipper lock trend has run since 2024, and the previous-generation leader, FunGear, has already dropped off the charts. Once a new mechanic surfaces on TikTok, ideally you're live and buying installs within one to two months.

Where the read could be wrong:

• If its weekly new installs fall below 20k by the end of 2026 and its category rank keeps sliding, the paid acquisition didn't pay back and it stopped. That would mean this playbook no longer makes money in this category;
• If Google moves it back to Personalization, or a batch of zipper lock apps that also switched categories quickly crowd the chart, the category loophole has been spotted by others;
• If the new mechanic you find already has five or six accounts with the same "Download" titles posting on TikTok after a single search, you're too late.