# Stack Testers Flow Friend vs Proton Authenticator & 2FA

The clearest difference is review sentiment: Proton Authenticator & 2FA at 58% against Stack Testers Flow Friend's 0%. Proton Authenticator & 2FA also leads on update cadence (weekly vs every 8 months) and chart position (#152 vs unranked). Stack Testers Flow Friend's advantage is iOS requirement (13.0 vs 17.0). On price, ads, in-app purchases and monetization model there is nothing between them.

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

Stack Testers Flow Friend ships an update every 8 months, Proton Authenticator & 2FA weekly. The most recent releases landed on October 22, 2026 and November 1, 2026 respectively.

## The numbers

| Metric | Stack Testers Flow Friend | Proton Authenticator & 2FA |
| --- | --- | --- |
| Price | Free | Free |
| Rating | — | **[4.6 (593 ratings)](https://appshunter.io/ios/app/proton-authenticator-and-2fa/id6741758667/reviews)** |
| Number of ratings | — | **593** |
| Positive reviews | 0.0% of reviews | **57.6% of reviews** |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 8 months | **Weekly** |
| Monetization | Free | Free |
| Best chart rank | — | **#152** |
| Size | 32 MB | 120 MB |
| Requires iOS | **13.0** | 17.0 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, Apple Watch |
| Age rating | 4+ | 4+ |
| Developer | [Lewis Holmes](https://appshunter.io/developer/1454834389) | [Proton AG](https://appshunter.io/developer/979659484) |

## What reviewers say

### Stack Testers Flow Friend

[App page](https://appshunter.io/ios/app/stack-testers-flow-friend/id1454834655)

This mobile toolkit assists environmental engineers with on-site calculations for stack testing. Quickly determine velocity and volume flow by inputting stack size and gas conditions, eliminating the need for manual calculations or laptops. It also aids in calculating differential pressure cell mA output for data logging.

**Highlights:** Velocity and volume flow calculations, Input stack size and gas conditions, Differential pressure cell mA output calculation, Preloaded Engineers Note Book content, On-site calculation tool

**Features:** macOS Compatibility

**In-app purchases:** none


### Proton Authenticator & 2FA

[App page](https://appshunter.io/ios/app/proton-authenticator-and-2fa/id6741758667)

**Currently charting:** #152 Top Free · Productivity (US App Store)

Securely manage your two-factor authentication codes with an open-source, end-to-end encrypted authenticator app. It offers seamless cross-device syncing, effortless import from other apps, and robust backup options, all protected by strict Swiss privacy laws. Take control of your digital security with a trusted and private solution.

**Highlights:** End-to-end encrypted iCloud sync, Effortless import from other authenticators, Secure backup and export, Swiss privacy by design, Open source and transparent, Offline support

**Features:** macOS Compatibility, Apple Watch app, Vision Pro support

**In-app purchases:** none

**What reviewers like**

- 🚀 Cross-platform support
- 🔒 Secure cloud sync
- 👍 Easy import from other authenticators
- 🚀 Convenient 'next' feature for codes

**What reviewers complain about**

- 🐛 Buggy UI (scrolling jitters, random sorting)
- 👎 Lack of customization options (pin favorites, change icons)
- 🐛 Sync/login issues on iPad

**Reported bugs**

- Sync/login loop on iPad
- 2FA input broken on non-iPhone devices
- Screen strobing on iPad
- Duplicate entries after import

**Requested features**

- PIN unlock for desktop
- Alphabetical sorting option
- Export function (not just Proton-specific backup)
- Native macOS app
- Option to hide item icons


## Frequently asked questions

### Is Stack Testers Flow Friend free?

Stack Testers Flow Friend is free to download, with no in-app purchases.

### Is Proton Authenticator & 2FA free?

Proton Authenticator & 2FA is free to download, with no in-app purchases.

### Do Stack Testers Flow Friend or Proton Authenticator & 2FA have ads?

Neither Stack Testers Flow Friend nor Proton Authenticator & 2FA shows ads.

### Which is updated more often, Stack Testers Flow Friend or Proton Authenticator & 2FA?

Stack Testers Flow Friend ships an update every 8 months, and Proton Authenticator & 2FA weekly. Most recently, Stack Testers Flow Friend was updated on October 22, 2026 and Proton Authenticator & 2FA on November 1, 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.*