# Duo Authenticator vs Corpad Cathodic Protection

The clearest difference is ads: Corpad Cathodic Protection at none against Duo Authenticator's shown. Duo Authenticator's advantage is update cadence (monthly vs every 4 months). On price, in-app purchases, device support and iOS requirement there is nothing between them.

Both are free to download. Duo Authenticator sells 3 in-app purchases, starting at $3.99 per 7 days and Corpad Cathodic Protection sells 1 in-app purchase, starting at $9.99 per month. Whichever you choose, the download price is not the number that matters.

Duo Authenticator ships an update monthly, Corpad Cathodic Protection every 4 months. The most recent releases landed on October 9, 2026 and October 11, 2026 respectively.

## The numbers

| Metric | Duo Authenticator | Corpad Cathodic Protection |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.2 (24 ratings)](https://appshunter.io/ios/app/duo-authenticator/id1665454984/reviews)** | — |
| Number of ratings | **24** | — |
| Positive reviews | 50.0% of reviews | — |
| In-app purchases | Yes | Yes |
| Ads | Yes | **No** |
| Update frequency | **Monthly** | Every 4 months |
| Monetization | Free with in-app purchases | — |
| Size | 60 MB | 49 MB |
| Requires iOS | 16.6 | **15.5** |
| Devices | iPhone | **iPhone, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [Petr Polasek](https://appshunter.io/developer/1613323784) | [Andrei Lomtev](https://appshunter.io/developer/1714768821) |

## What reviewers say

### Duo Authenticator

[App page](https://appshunter.io/ios/app/duo-authenticator/id1665454984)

Enhance your online security with this multi-factor authentication app. It provides an extra layer of protection for your accounts by generating time-sensitive codes, even when offline. Secure your sensitive information with ease and peace of mind.

**Highlights:** Quick and easy setup, Wide service compatibility, Time-sensitive security codes, Offline code generation, End-to-end encryption, Security code protection

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

**In-app purchases (3)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Premium 1 Week | $3.99 | per 7 days |
| Premium 1 Month | $9.99 | per month |
| Premium 1 Year | $29.99 | per year |


### Corpad Cathodic Protection

[App page](https://appshunter.io/ios/app/corpad-cathodic-protection/id6471076169)

**Features:** macOS Compatibility

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Corpad Premium | $9.99 | per month |


## Frequently asked questions

### Is Duo Authenticator free?

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

### Is Corpad Cathodic Protection free?

Corpad Cathodic Protection is free to download, with in-app purchases available.

### Do Duo Authenticator or Corpad Cathodic Protection have ads?

Duo Authenticator shows ads; Corpad Cathodic Protection does not.

### Which is updated more often, Duo Authenticator or Corpad Cathodic Protection?

Duo Authenticator ships an update monthly, and Corpad Cathodic Protection every 4 months. Most recently, Duo Authenticator was updated on October 9, 2026 and Corpad Cathodic Protection on October 11, 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.*