# Duocortex vs Kern

The clearest difference is in-app purchases: Duocortex at none against Kern's 3. Duocortex also leads on iOS requirement (15.6 vs 17.0). On price, update cadence, ads and device support there is nothing between them.

Both are free to download. Kern sells 3 in-app purchases, starting at $5.99 per month. Duocortex asks for nothing beyond the download.

Duocortex ships an update every 11 days, Kern fortnightly. The most recent releases landed on October 5, 2026 and October 7, 2026 respectively.

## The numbers

| Metric | Duocortex | Kern |
| --- | --- | --- |
| Price | Free | Free |
| Rating | — | **[5.0 (2 ratings)](https://appshunter.io/ios/app/kern-remember-what-you-read/id6777347570/reviews)** |
| Number of ratings | — | **2** |
| Positive reviews | — | 100.0% of reviews |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | **Every 11 days** | Fortnightly |
| Monetization | — | Free with in-app purchases |
| Size | 40 MB | 23 MB |
| Requires iOS | **15.6** | 17.0 |
| Devices | **iPhone, iPod** | iPhone |
| Age rating | 12+ | 4+ |
| Developer | [Duocortex](https://appshunter.io/developer/1828861021) | [Quantum IT](https://appshunter.io/developer/1650178784) |

## What reviewers say

### Duocortex

[App page](https://appshunter.io/ios/app/duocortex/id6749133589)

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

**In-app purchases:** none


### Kern

[App page](https://appshunter.io/ios/app/kern-remember-what-you-read/id6777347570)

This app helps you retain knowledge from books you've read by creating interactive flashcards. It uses spaced repetition to resurface information as it begins to fade, supporting both fiction and non-fiction content. Review your library offline and see an honest picture of what you remember.

**Highlights:** Spaced repetition flashcards, Supports fiction and non-fiction, Offline review capability, Interactive cards, No account required, Book fading visualization

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

**In-app purchases (3)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Kern Plus (Monthly) | $5.99 | per month |
| Kern Plus (Annual) | $49.99 | per year |
| Unlock One Book | $3.99 | one-time |


## Frequently asked questions

### Is Duocortex free?

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

### Is Kern free?

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

### Do Duocortex or Kern have ads?

Neither Duocortex nor Kern shows ads.

### Which is updated more often, Duocortex or Kern?

Duocortex ships an update every 11 days, and Kern fortnightly. Most recently, Duocortex was updated on October 5, 2026 and Kern on October 7, 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.*