# why数理 vs TiYi

The clearest difference is in-app purchases: why数理 at none against TiYi's 3. why数理 also leads on ads (none vs shown) and iOS requirement (11.0 vs 18.0). TiYi's advantage is update cadence (every 5 days vs fortnightly). On price and device support there is nothing between them.

Both are free to download. TiYi sells 3 in-app purchases, starting at $0.99 per month. why数理 asks for nothing beyond the download.

why数理 ships an update fortnightly, TiYi every 5 days. The most recent releases landed on November 3, 2026 and October 31, 2026 respectively.

## The numbers

| Metric | why数理 | TiYi |
| --- | --- | --- |
| Price | Free | Free |
| Rating | — | **[2.2 (6 ratings)](https://appshunter.io/ios/app/tiyi/id6768071550/reviews)** |
| Number of ratings | — | **6** |
| Positive reviews | — | 50.0% of reviews |
| In-app purchases | **No** | Yes |
| Ads | **No** | Yes |
| Update frequency | Fortnightly | **Every 5 days** |
| Monetization | — | Free |
| Size | 71 MB | 96 MB |
| Requires iOS | **11.0** | 18.0 |
| Devices | iPhone, iPad, iPod | **iPhone, iPad, Mac, Apple TV** |
| Age rating | 4+ | 4+ |
| Developer | [靖一 陈](https://appshunter.io/developer/1529972276) | [Weigan Technology (Shenzhen) Co., Ltd.](https://appshunter.io/developer/1896482773) |

## What reviewers say

### why数理

[App page](https://appshunter.io/ios/app/why/id1539375758)

**Features:** macOS Compatibility

**In-app purchases:** none


### TiYi

[App page](https://appshunter.io/ios/app/tiyi/id6768071550)

This app acts as a VPN client that allows you to import your existing VPN configurations from various sources. Connect to your authorized servers with a single tap, manage nodes, and choose your preferred routing modes. It offers a consistent experience across iPhone, iPad, and Mac.

**Highlights:** Import subscription URLs, Supports various protocols (VMess, VLESS, Trojan, etc.), One-tap connection, Node search and sorting, Latency testing, Multiple routing modes, iCloud sync for profiles

**Features:** Family Sharing, Vision Pro support

**In-app purchases (3)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Upgrade to Monthly VIP | $0.99 | per month |
| Upgrade to Yearly VIP | $4.99 | per year |
| Upgrade to Lifetime VIP | $9.99 | one-time |


## Frequently asked questions

### Is why数理 free?

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

### Is TiYi free?

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

### Do why数理 or TiYi have ads?

TiYi shows ads; why数理 does not.

### Which is updated more often, why数理 or TiYi?

why数理 ships an update fortnightly, and TiYi every 5 days. Most recently, why数理 was updated on November 3, 2026 and TiYi on October 31, 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.*