# CastleKeyp vs ZenZettel

The clearest difference is in-app purchases: CastleKeyp at none against ZenZettel's 2. CastleKeyp also leads on ratings volume (4 vs 1). On price, rating, update cadence and ads there is nothing between them.

Both are free to download. ZenZettel sells 2 in-app purchases, starting at $0.99 per month. CastleKeyp asks for nothing beyond the download.

On the App Store both sit at effectively the same score — 5.0 for CastleKeyp against 5.0 for ZenZettel. Both are backed by a comparable volume of ratings — 4 and 1 respectively.

Both ship on a similar rhythm, roughly every 2 months. The most recent releases landed on November 3, 2026 and November 4, 2026 respectively.

## The numbers

| Metric | CastleKeyp | ZenZettel |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [5.0 (4 ratings)](https://appshunter.io/ios/app/castlekeyp/id1541685212/reviews) | [5.0 (1 ratings)](https://appshunter.io/ios/app/zenzettel/id6744944376/reviews) |
| Number of ratings | **4** | 1 |
| Positive reviews | 100.0% of reviews | — |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 2 months | Every 2 months |
| Monetization | **Free** | Freemium |
| Size | 48 MB | 41 MB |
| Requires iOS | 15.1 | 15.1 |
| Devices | iPhone, iPod | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [CastleKeyp Corporation](https://appshunter.io/developer/1541685214) | [Ising Digital Sarl](https://appshunter.io/developer/1685735618) |

## What reviewers say

### CastleKeyp

[App page](https://appshunter.io/ios/app/castlekeyp/id1541685212)

Securely store and manage all your sensitive personal information, from passwords to family details. Access your encrypted data from anywhere and share specific information with trusted contacts. Organize social circles and never miss important dates with an integrated calendar.

**Highlights:** End-to-end encrypted data storage, Securely store passwords, bank details, and personal profiles, Share specific information with trusted contacts, Organize social circles and custom groups, Integrated calendar for important dates, Contact management for family and friends

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


### ZenZettel

[App page](https://appshunter.io/ios/app/zenzettel/id6744944376)

This app helps you build knowledge by transforming fleeting thoughts into permanent insights. It features a minimalist interface inspired by Japanese aesthetics, secure local storage, and AI-powered idea development. Organize your thoughts with smart tagging and advanced filtering.

**Highlights:** Impermanent note capture, AI-powered idea transformation, Advanced filtering, Minimalist interface, Secure local storage, Markdown export

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (2)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Premium | $0.99 | per month |
| Premium | $9.99 | per year |


## Frequently asked questions

### Is CastleKeyp free?

CastleKeyp is free to download, with no in-app purchases.

### Is ZenZettel free?

ZenZettel is free to download, with in-app purchases available.

### Which has better reviews, CastleKeyp or ZenZettel?

CastleKeyp and ZenZettel are both rated 5.0 out of 5 on the App Store, from 4 and 1 ratings respectively.

### Do CastleKeyp or ZenZettel have ads?

Neither CastleKeyp nor ZenZettel shows ads.

### Which is updated more often, CastleKeyp or ZenZettel?

CastleKeyp ships an update every 2 months, and ZenZettel every 2 months. Most recently, CastleKeyp was updated on November 3, 2026 and ZenZettel on November 4, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*