# Boost.AI 英作文添削・共通テスト英語 vs 勉強ストップウォッチ

The clearest difference is in-app purchases: 勉強ストップウォッチ at none against Boost.AI 英作文添削・共通テスト英語's 3. 勉強ストップウォッチ also leads on update cadence (every 2 days vs every 4 days). Boost.AI 英作文添削・共通テスト英語's advantage is iOS requirement (15.0 vs 18.0). On price, ads and device support there is nothing between them.

Both are free to download. Boost.AI 英作文添削・共通テスト英語 sells 3 in-app purchases, starting at $5.99 per month. 勉強ストップウォッチ asks for nothing beyond the download.

Boost.AI 英作文添削・共通テスト英語 ships an update every 4 days, 勉強ストップウォッチ every 2 days. The most recent releases landed on October 28, 2026 and October 24, 2026 respectively.

## The numbers

| Metric | Boost.AI 英作文添削・共通テスト英語 | 勉強ストップウォッチ |
| --- | --- | --- |
| Price | Free | Free |
| Positive reviews | 90.5% of reviews | — |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | Every 4 days | **Every 2 days** |
| Monetization | Freemium | — |
| Size | 151 MB | 1 MB |
| Requires iOS | **15.0** | 18.0 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPad |
| Age rating | 4+ | 4+ |
| Developer | [ATSUSHI KIMURA](https://appshunter.io/developer/1829870349) | [Kazuchika Niwa](https://appshunter.io/developer/6793122634) |

## What reviewers say

### Boost.AI 英作文添削・共通テスト英語

[App page](https://appshunter.io/ios/app/boostai/id6749287559)

This AI-powered app offers instant English writing feedback, detailed explanations, and AI chat for deeper understanding. It supports various writing styles and learning goals, helping users improve their English proficiency anytime, anywhere.

**Highlights:** Instant AI essay correction, Detailed explanations for errors, Handwriting recognition for essays, AI chat for clarification, Learning history management, Diverse question formats, Flashcards and English news

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

**In-app purchases (3)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Boost Pro 月額プラン | $5.99 | per month |
| 3ヶ月 | $11.99 | per 3 months |
| Boost Pro 年額プラン | $39.99 | per year |


### 勉強ストップウォッチ

[App page](https://appshunter.io/ios/app/id6793122332)

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

**In-app purchases:** none


## Frequently asked questions

### Is Boost.AI 英作文添削・共通テスト英語 free?

Boost.AI 英作文添削・共通テスト英語 is free to download, with in-app purchases available.

### Is 勉強ストップウォッチ free?

勉強ストップウォッチ is free to download, with no in-app purchases.

### Do Boost.AI 英作文添削・共通テスト英語 or 勉強ストップウォッチ have ads?

Neither Boost.AI 英作文添削・共通テスト英語 nor 勉強ストップウォッチ shows ads.

### Which is updated more often, Boost.AI 英作文添削・共通テスト英語 or 勉強ストップウォッチ?

Boost.AI 英作文添削・共通テスト英語 ships an update every 4 days, and 勉強ストップウォッチ every 2 days. Most recently, Boost.AI 英作文添削・共通テスト英語 was updated on October 28, 2026 and 勉強ストップウォッチ on October 24, 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.*