Preview App vs Knockbox
Price, ratings, monetisation and update history for both apps, side by side ā with what reviewers say about each.
Preview App
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Do you want to preview what your app looks like on the app store in advance? Let me help you. First download this app and then edit your app information. You can see the 6.5-inch and 6.9-inch app preview.
Knockbox
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Knock once, and your phone buzzes. Knockbox turns one HTTP request into a push notification on your iPhone. Anything that can send a request can reach you: a deploy script, a cron job, a monitoring check, a CI pipeline, or a coding agent that has just finished a long task. If it needs your go-ahead before continuing, it can wait for your answer. curl -d "Build finished" https://your-server/api/v1/send/YOUR_TOKEN THE SERVER IS YOURS Knockbox is the client for a server you control. The server is open source and runs on a VPS, a NAS, or a Raspberry Pi at home. It holds its own Apple push key, so a notification goes from your machine to Apple and then to your phone, without passing through anyone in between. If you would rather not run anything, open knockbox.miramiao.com on your iPhone and you are connected ā no sign-up, no password. WHAT A MESSAGE CAN CARRY ⢠A Markdown body with headings, lists, links and syntax-highlighted code. ⢠Images, shown in the notification and kept with the message. ⢠Long text. The body is fetched as the notification lands rather than packed into it, so there is no length limit to work around. ⢠A title, a channel, and an interruption level: quiet, normal, or time sensitive when it has to break through Focus. REPLIES ⢠The sender can attach a set of options, or allow a free-text answer. ⢠Answer from the message itself. Your server posts the reply back to the address the sender gave, signed, and the sender takes it from there. ⢠The sender can set a deadline. After it passes the message reads "Reply window closed" and the server stops accepting ā you are never left thinking an answer went through. ⢠A message is answered once, and the answer is the same across your devices. CHANNELS ⢠One token per channel, so a noisy monitor and a personal reminder stay apart. ⢠Muting a channel truly stops it: the mute lives on the server, so nothing is sent at all. ⢠Search your history, mark as read, delete a message, or clear a channel. Deletions are real, on the device and on the server. MORE THAN ONE DEVICE Pair a second iPhone or iPad from a device that is already connected. Both receive everything and share read state. TRY IT WITHOUT A SERVER Demo mode fills the app with example messages and sends a sample notification, so you can see how it works before setting anything up. FREE, AND THAT IS ALL No ads, no analytics, no account with us, no in-app purchase, no subscription. The app is free and the server is open source. Server source code: https://github.com/aichy126/knockbox Public server: https://knockbox.miramiao.com How to send: https://knockbox.miramiao.com/docs Questions: info@miramiao.com
Screenshots
Verdict
The clearest difference is price: Knockbox at Free against Preview App's $1.99. Knockbox also leads on update cadence (daily vs every 13 months). Preview App's advantage is iOS requirement (15.6 vs 17.0). On ads, in-app purchases and device support there is nothing between them.
Scored on Price Ā· Rating Ā· Positive reviews Ā· Number of ratings Ā· Update frequency Ā· Ads Ā· In-app purchases Ā· Monetization Ā· Best chart rank Ā· Devices Ā· Requires iOS
Knockbox is free to download; Preview App costs $1.99 up front. Neither carries in-app purchases, so what you see is what you pay.
Preview App ships an update every 13 months, Knockbox daily. The most recent releases landed on October 8, 2026 and October 6, 2026 respectively.
| Parameter | Preview App | Knockbox |
|---|---|---|
| Price | $1.99 | Free ā better |
| Update frequency | Every 13 months | Daily ā better |
| Ads | No | No |
| In-app purchases | No | No |
| Devices | iPhone, iPod | iPhone, iPad |
| Requires iOS | 15.6 ā better | 17.0 |
| Further details ā not scored | ||
| Size | 8 MB | 7 MB |
| Age rating | 4+ | 4+ |
| Developer | Cangmu Technology Co., Ltd | č č |
In-app purchases
Preview App
No in-app purchases
Knockbox
No in-app purchases









