# CastleKeyp vs Subrain

The clearest difference is update cadence: Subrain at every 9 days against CastleKeyp's every 3 months. Subrain also leads on iOS requirement (12.0 vs 15.1). On price, review sentiment, ads and in-app purchases there is nothing between them.

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

CastleKeyp ships an update every 3 months, Subrain every 9 days. The most recent releases landed on September 28, 2026 and August 16, 2026 respectively.

## The numbers

| Metric | CastleKeyp | Subrain |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[5.0 (1 ratings)](https://appshunter.io/ios/app/castlekeyp/id1541685212/reviews)** | — |
| Number of ratings | **1** | — |
| Positive reviews | 100.0% of reviews | 100.0% of reviews |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 3 months | **Every 9 days** |
| Monetization | Free | Free |
| Size | 48 MB | 49 MB |
| Requires iOS | 15.1 | **12.0** |
| Devices | iPhone, iPod | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [CastleKeyp Corporation](https://appshunter.io/developer/1541685214) | [Jichan Hwang](https://appshunter.io/developer/1735193590) |

## 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


### Subrain

[App page](https://appshunter.io/ios/app/subrain/id6502538432)

This app helps you remember important information and life keywords that you might otherwise forget. Designed for minimalists, it offers a simple way to capture thoughts and serve as a personal milestone.

**Highlights:** Simple note-taking, Capture life keywords, Minimalist design, Acts as a milestone, Organize notes into pages

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

**In-app purchases:** none


## Frequently asked questions

### Is CastleKeyp free?

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

### Is Subrain free?

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

### Do CastleKeyp or Subrain have ads?

Neither CastleKeyp nor Subrain shows ads.

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

CastleKeyp ships an update every 3 months, and Subrain every 9 days. Most recently, CastleKeyp was updated on September 28, 2026 and Subrain on August 16, 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.*