Comparison

Preview App vs Knockbox

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

Preview App

Features
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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.

About

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 — 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 — 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

Preview App4 screens
Knockbox4 screens

Verdict

The call

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

CostPrice Ā· In-app purchases Ā· Ads Ā· Monetization

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.

UpkeepUpdate frequency

Preview App ships an update every 13 months, Knockbox daily. The most recent releases landed on October 8, 2026 and October 6, 2026 respectively.

Scorecard3 real differences Ā· 3 level
Preview App versus Knockbox: the parameters behind the verdict, then further details
ParameterPreview AppKnockbox
Price$1.99Free — better
Update frequencyEvery 13 monthsDaily — better
AdsNoNo
In-app purchasesNoNo
DevicesiPhone, iPodiPhone, iPad
Requires iOS15.6 — better17.0
Further details — not scored
Size8 MB7 MB
Age rating4+4+
DeveloperCangmu Technology Co., Ltd苗 苗

In-app purchases

None

Preview App

No in-app purchases

None

Knockbox

No in-app purchases

Questions

Is Preview App free?
Preview App costs $1.99, with no in-app purchases.
Is Knockbox free?
Knockbox is free to download, with no in-app purchases.
Do Preview App or Knockbox have ads?
Neither Preview App nor Knockbox shows ads.
Which is updated more often, Preview App or Knockbox?
Preview App ships an update every 13 months, and Knockbox daily. Most recently, Preview App was updated on October 8, 2026 and Knockbox on October 6, 2026.

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