Comparison

CastleKeyp vs ZenZettel

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

Head to head
About

CastleKeyp

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
Read full description

At every stage of life, CastleKeyp helps you organize and manage the business of life. Organize your important personal information, keep up relationships, and lighten the mental load. Store your sensitive personal information and access it from anywhere. End-to-end encryption protects your information for total privacy and security. Your information is just between you and the people you choose. Not even CastleKeyp can see it. Your CastleKeyp Profile: Home address, birthdates, allergies, family information and more - personal information you wouldn’t normally put online is entirely private and secure in your end-to-end encrypted CastleKeyp Profile. Only you and the people you choose to connect with on CastleKeyp can see it. Control what others see – share all or just parts of your Profile. Your Profile is free to create and share with as many CastleKeyp Contacts as you choose. Great for remembering birthdays, sending gifts and much more! Your end-to-end encrypted Keyp: Welcome to your very own online Keyp: a single, accessible place to store and organize all of your personal information, end-to-end encrypted. As secure as a password safe, it's a template for organizing your home life - store home utility account information, family blood types, frequent flier accounts - every bit of personal information, so you never lose track again. Have your partner or trusted family member join CastleKeyp and you can permission them to see your Keyp - manage life together. Otherwise, it's for your eyes only. Securely store information you need to manage the business of life. It will be there when you need it. One place, good for life. Connect better: Keep track of extended family and friends, with a fraction of the headache. Every CastleKeyp member updates their own Profile – so it's good information, right from the source - and no more trying to keep track of moves, contact information changes, children’s names, ages, allergies. Manage just your own CastleKeyp Profile instead of all of your contacts' cards. Have the useful information you need to reach the people who matter most in your life, for life. From a high school graduation to a wedding to a funeral and everything in between, reach your people when it matters most. Joining CastleKeyp is free, private and secure - invite your friends, family and community. You can connect with unlimited CastleKeyp members. Organize your social life: We all have different social circles – Book Club, Wine Club, PTA, Fantasy Football, Little League, volunteer organizations. Create Custom Groups to keep in touch more easily. Send emails, text or export contact information with a single tap. Use CastleKeyp's Holiday Cards Group, and export your addresses for the printer with a single tap. Or share sensitive personal information with a Partner or family member with CastleKeyp’s Pre-Set groups – clothing sizes for you and your family; SSNs and more with a Partner or family. Never miss an important date again: When does your passport expire? Put it into CastleKeyp, and you'll get a helpful reminder. All of your important dates populate automatically on the in-app Calendar. Birthdays and anniversaries for your CastleKeyp Contacts, expiration and due dates for your passport and more, all in one place. Get custom in-app and push notifications to stay on top of it all. Save time, money and hassle with reminders for expiration and due dates for passports, credit cards, property tax bills, insurance policies and more. Keyp your life in order - and spread the word! At every stage of life, CastleKeyp helps you organize and manage the business of life. All in one place.

About

ZenZettel

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
Read full description

Mindful Knowledge Building Key Features Impermanent note capture for quick thoughts Transformation workflow to develop ideas into permanent knowledge Smooth AI transformation with personnalisable prompt Advanced filtering by date, tags, and note status Beautiful, minimalist interface inspired by Japanese aesthetics Secure local storage with export options Intuitive navigation between review, capture, and organization Perfect for students, researchers, writers, and anyone who values thoughtful knowledge building. Turn your scattered thoughts into a connected web of wisdom. "In the garden of the mind, ZenZettel helps you plant seeds of thought and cultivate a forest of knowledge." Download ZenZettel and begin your journey toward mindful note-taking today. Transform fleeting thoughts into lasting wisdom ZenZettel brings the powerful Zettelkasten method to your mobile device with a zen-like simplicity that encourages deep thinking and meaningful connections. Capture & Cultivate Quick Capture: Jot down impermanent notes instantly when inspiration strikes Mindful Review: Transform raw thoughts into refined, permanent knowledge Smart Tagging: Organize ideas with flexible tag systems for easy discovery The Zen Philosophy Two-Stage Thinking: Start with impermanent notes, then mindfully transform them into permanent insights Clutter-Free Interface: Clean, distraction-free design that focuses your mind on what matters Intentional Organization: Sort by status, date, or tags to find exactly what you need Knowledge Management Permanent Notes: Create a personal knowledge base with rich markdown support Seamless Export: Share your insights with full markdown export capabilities Privacy Policy: https://zenzettel.vercel.app/#privacy Terms of Use (EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

Screenshots

CastleKeyp4 screens
ZenZettel4 screens

Verdict

The call

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.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

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

ReceptionRating · Positive reviews · Number of ratings

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.

UpkeepUpdate frequency

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

Scorecard3 real differences · 7 level
CastleKeyp versus ZenZettel: the parameters behind the verdict, then further details
ParameterCastleKeypZenZettel
PriceFreeFree
Rating5.0 (4 ratings)5.0 (1 ratings)
Positive reviews100.0% of reviews—
Number of ratings4 — better1
Update frequencyEvery 2 monthsEvery 2 months
AdsNoNo
In-app purchasesNo — betterYes
MonetizationFree — betterFreemium
DevicesiPhone, iPodiPhone, iPad, iPod — better
Requires iOS15.115.1
Further details — not scored
Size48 MB41 MB
Age rating4+4+
DeveloperCastleKeyp CorporationIsing Digital Sarl

Customer experience

CastleKeyp

All ratings1 ratings
Positive100.0%
Neutral0.0%
Negative0.0%
Written reviews1 reviews
Positive100.0%
Neutral0.0%
Negative0.0%

ZenZettel

All ratings1 ratings
Positive100.0%
Neutral0.0%
Negative0.0%

In-app purchases

None

CastleKeyp

No in-app purchases

2 purchases

ZenZettel

Subscriptions2
  • Premium$0.991 Month
  • Premium$9.991 Year

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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