# Fartlek Interval Trainer vs ZentnlApp

The clearest difference is in-app purchases: ZentnlApp at none against Fartlek Interval Trainer's 4. ZentnlApp also leads on iOS requirement (15.1 vs 26.0). On price, update cadence, ads and device support there is nothing between them.

Both are free to download. Fartlek Interval Trainer sells 4 in-app purchases, starting at $0.99 per month. ZentnlApp asks for nothing beyond the download.

Fartlek Interval Trainer ships an update every 9 days, ZentnlApp every 2 weeks. The most recent releases landed on November 3, 2026 and September 23, 2026 respectively.

## The numbers

| Metric | Fartlek Interval Trainer | ZentnlApp |
| --- | --- | --- |
| Price | Free | Free |
| Positive reviews | 75.0% of reviews | — |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | **Every 9 days** | Every 2 weeks |
| Monetization | Freemium | — |
| Size | 86 MB | 27 MB |
| Requires iOS | 26.0 | **15.1** |
| Devices | iPhone, Apple Watch | iPhone, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Richard English](https://appshunter.io/developer/1537547687) | [WAVR International AB](https://appshunter.io/developer/1755372558) |

## What reviewers say

### Fartlek Interval Trainer

[App page](https://appshunter.io/ios/app/fartlek-interval-trainer/id1537547685)

This running app automatically detects spontaneous intervals during Fartlek runs, providing live color-coded feedback on your effort. It also functions as a powerful timer for structured workouts like HIIT and Tabata, offering detailed metrics and syncing with Strava and Apple Health.

**Highlights:** Auto-detection of Fartlek intervals, Live color-coded effort feedback, Structured workout timer (HIIT, Tabata), Detailed interval metrics, Strava and Apple Health integration, Advanced effort level detection

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

**In-app purchases (4)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Monthly | $0.99 | per month |
| Annual | $6.99 | per year |
| RemoveAds | $0.99 | one-time |
| Lifetime | $14.99 | one-time |


### ZentnlApp

[App page](https://appshunter.io/ios/app/zentnlapp/id6738145678)

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is Fartlek Interval Trainer free?

Fartlek Interval Trainer is free to download, with in-app purchases available.

### Is ZentnlApp free?

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

### Do Fartlek Interval Trainer or ZentnlApp have ads?

Neither Fartlek Interval Trainer nor ZentnlApp shows ads.

### Which is updated more often, Fartlek Interval Trainer or ZentnlApp?

Fartlek Interval Trainer ships an update every 9 days, and ZentnlApp every 2 weeks. Most recently, Fartlek Interval Trainer was updated on November 3, 2026 and ZentnlApp on September 23, 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.*