# Thetis Authenticator vs Si4Keyboard

The clearest difference is price: Thetis Authenticator at Free against Si4Keyboard's $0.99. Thetis Authenticator also leads on iOS requirement (13.0 vs 17.6). Si4Keyboard's advantage is update cadence (fortnightly vs every 9 months). On ads, in-app purchases and device support there is nothing between them.

Thetis Authenticator is free to download; Si4Keyboard costs $0.99 up front. Neither carries in-app purchases, so what you see is what you pay.

Thetis Authenticator ships an update every 9 months, Si4Keyboard fortnightly. The most recent releases landed on October 10, 2026 and October 17, 2026 respectively.

## The numbers

| Metric | Thetis Authenticator | Si4Keyboard |
| --- | --- | --- |
| Price | **Free** | $0.99 |
| Rating | **[3.5 (4 ratings)](https://appshunter.io/ios/app/thetis-authenticator/id6648759010/reviews)** | — |
| Number of ratings | **4** | — |
| Positive reviews | 60.0% of reviews | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 9 months | **Fortnightly** |
| Monetization | Free | — |
| Size | 3 MB | 14 MB |
| Requires iOS | **13.0** | 17.6 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPad |
| Age rating | 4+ | 17+ |
| Developer | [Razzo Tech Corporation](https://appshunter.io/developer/1566501237) | [文焕 陈](https://appshunter.io/developer/1810161184) |

## What reviewers say

### Thetis Authenticator

[App page](https://appshunter.io/ios/app/thetis-authenticator/id6648759010)

Manage your FIDO2 security keys for passwordless login and two-factor authentication. Supports NFC and Type-C connections for seamless integration across devices. Offers one-time password management for services not yet supporting FIDO2.

**Highlights:** FIDO2 passwordless login, Enhanced two-factor authentication, One-time password management, Optimized for iPad, NFC and Type-C compatibility, Cross-platform support, Phishing-resistant authentication

**In-app purchases:** none


### Si4Keyboard

[App page](https://appshunter.io/ios/app/si4keyboard/id6745263713)

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is Thetis Authenticator free?

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

### Is Si4Keyboard free?

Si4Keyboard costs $0.99, with no in-app purchases.

### Do Thetis Authenticator or Si4Keyboard have ads?

Neither Thetis Authenticator nor Si4Keyboard shows ads.

### Which is updated more often, Thetis Authenticator or Si4Keyboard?

Thetis Authenticator ships an update every 9 months, and Si4Keyboard fortnightly. Most recently, Thetis Authenticator was updated on October 10, 2026 and Si4Keyboard on October 17, 2026.

---

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