# i vs 小牛错题本

The clearest difference is in-app purchases: i at none against 小牛错题本's 4. i also leads on iOS requirement (9.0 vs 12.0). On price, update cadence, ads and device support there is nothing between them.

Both are free to download. 小牛错题本 sells 4 in-app purchases, starting at $2.99 per month. i asks for nothing beyond the download.

i ships an update fortnightly, 小牛错题本 monthly. The most recent releases landed on October 27, 2026 and October 24, 2026 respectively.

## The numbers

| Metric | i | 小牛错题本 |
| --- | --- | --- |
| Price | Free | Free |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | **Fortnightly** | Monthly |
| Size | 34 MB | 105 MB |
| Requires iOS | **9.0** | 12.0 |
| Devices | iPhone, iPod | iPhone, iPod |
| Age rating | 4+ | 4+ |
| Developer | [CG Midea Heating & Ventilating Equipment CO., Ltd.](https://appshunter.io/developer/918398670) | [深圳市云领天下科技有限公司](https://appshunter.io/developer/725440563) |

## What reviewers say

### i

[App page](https://appshunter.io/ios/app/i-comfy/id1499744043)

**Features:** macOS Compatibility

**In-app purchases:** none


### 小牛错题本

[App page](https://appshunter.io/ios/app/id6474232623)

**Features:** macOS Compatibility

**In-app purchases (4)**

| Purchase | Price | Billing |
| --- | --- | --- |
| 小牛错题本连续包月（1个月） | $2.99 | per month |
| 小牛错题本连续包季（3个月） | $5.99 | per 3 months |
| 小牛错题本会员1个月 | $3.99 | one-time |
| 小牛错题本会员6个月 | $14.99 | one-time |


## Frequently asked questions

### Is i free?

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

### Is 小牛错题本 free?

小牛错题本 is free to download, with in-app purchases available.

### Do i or 小牛错题本 have ads?

Neither i nor 小牛错题本 shows ads.

### Which is updated more often, i or 小牛错题本?

i ships an update fortnightly, and 小牛错题本 monthly. Most recently, i was updated on October 27, 2026 and 小牛错题本 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.*