"即時通 is back": a nostalgic chat app built by one person hit #1 on Taiwan's overall chart in a day. Then what?

On Oct 28, a Taiwanese indie developer launched "延遲通" (Yanchi Tong) on the App Store, a mobile chat and dating app modeled on Yahoo! Kimo Instant Messenger. Four days later it was #1 on Taiwan's iPhone free overall chart, with no paid acquisition, just a wave of nostalgia on Threads from a generation that grew up on it. Four days after that, it had slipped to #13, now dragging a plagiarism accusation, questions about Chinese ownership, and a monthly server bill of NT$200K. Here's what it is, why it blew up, where the money comes from, who's competing with it, and whether you can use the same playbook somewhere else.

One line: "I was born in 79"

On Nov 1, a Taiwanese user named 紀澄 Abby Chi posted on Threads: "I was born in 79, saw that nostalgic 'Instant Messenger' come back today. Has anyone downloaded it? It's now called '延遲通'", followed by "Back then we'd pretend we were offline, or send one line and a link 🤣". The post got only 3.8K views, but that same stretch of Threads was full of posts like it: "OMG I love it!! Instant Messenger is back, even the ding sound is there!!!" "Add me as a friend, let's relive the good old days" (reported by 緯來新聞, 11-02).

"79 年次" means born in 1990. Taiwan's seventh and eighth graders (born in the 1980s and 90s) would come home from school and log into Instant Messenger first thing, checking who was online, changing their status to something melancholy, and poking a friend who wasn't replying. Yahoo shut it down in Jul 2018 17, and nothing replaced it. 延遲通 turned that empty space into a mobile app, and the people most active on Taiwan's Threads happen to be exactly that generation.

What it is

The store page opens with: "Remember rushing home from school, first thing you'd do was check who's online?" Almost everything in it was already in Instant Messenger or MSN:

• Two retro Windows-style skins, purple and blue, with pixel fonts and the ding sound;
• "Nudge" that shakes the recipient's window, and a talking snail doll that mirrors the old "嗆聲娃娃" (trash-talk dolls);
• Friend groups with statuses like "Online / Busy / Out to eat / Back soon," and the option to permanently appear offline to specific friends;
• Chat rooms (island-wide, by region, by interest), family groups, and small multiplayer games (Gomoku, dark chess, minesweeper, Connect Four);
• Modern features too: voice and video calls, and sending photos and files.

This matters: it isn't just a skin, it's a real social app where you can chat and make friends. Nostalgic users who come in find strangers to talk to and games to play. 11-03 A five-star review: "My boyfriend and I... already blew up four mini-games, spent the whole day stuck in lag playing mini-games... got all my friends in to play mini-games".

The developer, chen Zihao, has only this one app; the official Threads account, "回憶製造所|延遲通", calls itself "小蝸牛" (Little Snail). It's iOS-only and Chinese-only.

How fast it rose, and how fast it fell

Source: App Store Taiwan charts, 11-01 to 11-06. Later, the store page showed 11-06 ratings averaging 507 4.65 stars.

Nov 2 it passed 红果短剧, Monster Hunter and Meta AI on the overall chart. Ratings only started climbing two days after the ranking did; by 11-02 it was already #1 with a rating still at 0, probably because the early builds didn't prompt for ratings (inference), so the rating count undercounts early downloads.

But the curve is clear: over three days the overall chart ranking fell from 1 to 13, and only the social category still holds #1. This is an event, not a long climb.

Where users came from: Threads, then media

• Organic Threads buzz was the main channel. The developer wrote on Threads: "I didn't do any online marketing at all... the organic traffic that followed really scared me." The official account also kept personally responding to criticism and posting download links on Threads.
• 媒体跟进:11-02 当天 NOWnews、緯來新聞、Yahoo 新聞、JUKSY 都发了,标题是「即時通復活」「爆紅登冠軍」。「冠军」这两个字又带来下一轮下载。
• Friends bringing friends: messaging apps only work when your contacts join, and the product has QR codes and links for adding friends (inferred to be a third source).
• Very little TikTok: searching "延遲通" turns up only a few small accounts' videos with a few hundred views. One caption reads "iPhone: search 延遲通 in the App Store," which looks like promotional content from a promo account. Whether it was arranged by the official team is unverified.
• Ads: no Meta, TikTok or Google ad activity found.

Where the money comes from: some, but small, and not enough to cover the bills

The app is free to download. Monetization is a set of small in-app purchases (App Store Taiwan page, 11-06): 延遲通 VIP NT$90, 懷舊豪華包 NT$90, "請蝸牛喝珍奶" (Treat the Snail to Bubble Tea) NT$30, Rocket VIP monthly fee NT$120, plus larger photo albums, an ad-free subscription, and ads. The latest version renamed members to "尊榮蝸牛" (Honored Snail) and "火箭蝸牛" (Rocket Snail) and added a scrolling marquee, name effects and gold borders. What's being sold is status inside the chat rooms.

It never reached the Taiwan overall grossing chart. Its best social grossing rank was #11-04, 31,11-06 dropping to #59. People are paying, but at a small scale, and the exact amount is unknown.

On the cost side, the developer said on Threads that they started out using only free tiers of Firebase and Cloudflare. "Even if user growth stops, operating costs are about NT$200K a month" (roughly US$6,200), the family feature was once paused for lack of funds, and the next version "will add a small amount of ads." Real-time chat, voice and video calls, and stranger chat rooms are each server-hungry. After the spike, the first thing to arrive wasn't revenue, it was the bill.

Three things it got criticized for

• Plagiarism. Designer @chimin_design posted about a free web-based nostalgia messenger, GG-Messenger, on Threads on Oct 15. On Nov 2 she posted that 延遲通's characters ("小雅"), menu text, bubble tea gifts, dice rolling, and even friend-list entries like "阿傑 籃球隊" and "段考倒數 3 天" matched hers. "I never authorized anyone... to charge money with it," she wrote, and said she would appeal to Apple. The post got 286K views and 6.8K likes. The developer replied that they "referenced publicly available nostalgic interfaces and resources." Later versions renamed dice to "蝸牛骰盅" (Snail Dice Cup), gifts to "蝸牛快遞" (Snail Express), and redrew all the dolls. A one-star App Store review also said: "Calls itself a tribute to nostalgia but it's all copycat... plagiarism to make money" (11-03).
• Chinese ownership and censorship. Some users said sensitive words triggered "訊息傳送失敗" (message failed to send) and suspected the developer was from mainland China (緯來新聞, 11-02). "Zihao" is a Pinyin spelling, and that got used as a reason too. The developer states they are an individual Taiwanese developer, have no Chinese investment, host servers in Google Cloud regions in Taiwan and the US, and encrypt private messages end-to-end. None of this can be verified from the outside. In Taiwan, that kind of suspicion can break growth outright.
• Name. It went from "Delay Messenger" to "Delay Messenger – Retro Chat Rooms & Dating Chat App", then to the current "Delay Messenger – Retro Dating & Mini Games". Renamed twice in one week. Our guess: dodging the "即時通" name tied to Yahoo, while swapping in new search keywords.

Basics also came up: "No notifications at all?" (one-star, 11-04). Over 8 days they shipped more than five versions, mostly fixing server issues and crashes.

Who it's competing with

Almost none, and that's why it could take off:

No Android version. Media describe it as "currently iOS only."

What to learn from it

延遲通's edge is the nostalgia itself: the interface, sounds, the ding, and the stealth-status etiquette of that era, not feature innovation. That layer pulls people in very fast, but it's also very easy to copy and very easy to get sued over.

What you can take from this is a formula: a social product a big company shut down, with a generation's shared memories + a social platform that generation is currently gathered on + a line like "XX is back". In Taiwan, 延遲通 used Instant Messenger and Threads. The same structure has existed elsewhere with MSN (Latin America, Europe), Feixin and early QQ (mainland China), mixi (Japan), and Orkut (Brazil, India). Nostalgia gets day one; retention takes chat rooms, family groups and mini-games; revenue comes from badges and effects.

If it were you

The verdict: learnable, but following it isn't a great bet. Copying it in Taiwan now is already late: it holds the top spot, its buzz is fading, and someone is suing it. Running the same formula in another country is worth testing, but it's a one-time spike, not a stable business, and real-time chat server costs will arrive before the revenue does.

Who it suits: a solo developer or small team of 1–2 people who has built real-time chat or social backends and knows how to keep server costs down; someone who is part of the generation a nostalgic product targets and can hold a conversation on the local social platform; someone treating it as a low-cost experiment who can accept that it might drop to zero within three weeks.

Who it doesn't suit: anyone who wants to build another Instant Messenger clone in Taiwan (you'd be a copy of 延遲通, which itself keeps getting asked where it came from); anyone without backend experience planning to ride out traffic on free tiers (that's exactly how 延遲通 got caught by its bill); anyone aiming for long-term subscription revenue (the nostalgia wave fades within a week, and whether the people who stay will stay at all, 延遲通 itself can't tell yet).

How to do it:

• Pick a product whose original is dead, has no local replacement, and whose users are now 30–45 years old;
• Draw the interface, characters, copy and sounds yourself from day one, don't touch the original trademark, and don't touch other people's fan works. 延遲通's biggest trouble came from exactly this;
• Ship stranger chat rooms and two or three multiplayer mini-games in version one. Don't just build a shell for chatting with old friends;
• Charge only small status purchases (badges, entrance effects, name colors), and keep chat rooms and games free;
• Launch on iOS and Android together, or web first. Launching on one platform only hands the other half of users to whoever comes next.

How to get users: post on the platform where that generation gathers now, using a line they recognize immediately ("XX is back"). Have the developer speak up personally to tell the story and answer criticism. Prepare an explainer and screenshots for media so they'll come to you when it takes off. Put your identity, company, server location, and whether chats are encrypted in a prominent place before launch.

Timing: there's no hard calendar deadline. But a topic like this usually only spikes once per market, and whoever says the "XX is back" line first owns the window.

What would show you read it wrong: ① 延遲通 still holds a top-3 spot on Taiwan's social free chart in December and its grossing rank climbs back into the top 30. That would mean nostalgia actually retained people and became a real social business, not a one-off event. ② Apple pulls it for infringement or it's forced to change its core interface. That would mean the legal risk of this path is bigger than it looks. ③ Someone repeats the same playbook in another market and spikes a second time. That would mean the formula is replicable and worth racing for the next one.

Data and sources

• Charts and ratings: App Store Taiwan free, grossing and social category charts, 11-01 to 11-06. Store page and version history read 11-06.
• In-app purchase prices: App Store Taiwan page, 11-06, not verified by placing an order.
• User posts: Threads @abbychi_1207 (about 11-01), @chimin_design (about 11-02), and the official account @retro.app.lab's statements and explanations (11-01 to 11-02).
• Media: NOWnews, 緯來新聞, JUKSY, Yahoo News, all 11-02.
• Monthly running cost of about NT$200k, the developer's identity, server locations and encryption claims all come from the developer's own statements and are unverified.
• "Low ratings undercount early downloads", "renaming was to dodge a trademark" and "friend invites were one of the sources" are all inferences.