# ISME Microbes vs Keystone Exam Prep

The clearest difference is in-app purchases: ISME Microbes at none against Keystone Exam Prep's 10. ISME Microbes also leads on iOS requirement (13.4 vs 15.5). On price, update cadence, ads and device support there is nothing between them.

Both are free to download. Keystone Exam Prep sells 10 one-off in-app purchases. ISME Microbes asks for nothing beyond the download.

ISME Microbes ships an update every 5 months, Keystone Exam Prep every 7 months. The most recent releases landed on October 26, 2026 and October 22, 2026 respectively.

## The numbers

| Metric | ISME Microbes | Keystone Exam Prep |
| --- | --- | --- |
| Price | Free | Free |
| Rating | — | **[2.0 (1 ratings)](https://appshunter.io/ios/app/keystone-exam-prep-live-app/id6465206824/reviews)** |
| Number of ratings | — | **1** |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | **Every 5 months** | Every 7 months |
| Monetization | — | Free with in-app purchases |
| Size | 82 MB | 145 MB |
| Requires iOS | **13.4** | 15.5 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [International Society for Microbial Ecology](https://appshunter.io/developer/1394492884) | [Online Learning](https://appshunter.io/developer/1790866777) |

## What reviewers say

### ISME Microbes

[App page](https://appshunter.io/ios/app/isme-microbes/id1394492885)

**Features:** macOS Compatibility

**In-app purchases:** none


### Keystone Exam Prep

[App page](https://appshunter.io/ios/app/keystone-exam-prep-live-app/id6465206824)

Prepare for competitive exams with extensive mock tests and practice questions. Access daily current affairs, quizzes, and detailed performance analysis. Offers multilingual support for a personalized learning experience.

**Highlights:** Mock tests for competitive exams, 50,000+ practice questions, Daily current affairs, Daily free quizzes, Detailed performance analysis, Multilingual support

**In-app purchases (10)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Package - 18900 | $199.99 | one-time |
| Package - 19900 | $199.99 | one-time |
| Package - 21900 | $199.99 | one-time |
| Package - 27900 | $299.99 | one-time |
| Package - 39900 | $399.99 | one-time |
| Package - 44900 | $449.99 | one-time |
| Package - 54900 | $499.99 | one-time |
| Package - 69900 | $699.99 | one-time |
| Package - 79900 | $799.99 | one-time |
| Package - 89900 | $899.99 | one-time |


## Frequently asked questions

### Is ISME Microbes free?

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

### Is Keystone Exam Prep free?

Keystone Exam Prep is free to download, with in-app purchases available.

### Do ISME Microbes or Keystone Exam Prep have ads?

Neither ISME Microbes nor Keystone Exam Prep shows ads.

### Which is updated more often, ISME Microbes or Keystone Exam Prep?

ISME Microbes ships an update every 5 months, and Keystone Exam Prep every 7 months. Most recently, ISME Microbes was updated on October 26, 2026 and Keystone Exam Prep on October 22, 2026.

---

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