# Timeline vs Interval Timer for HIIT | Cero

The clearest difference is ads: Timeline at none against Interval Timer for HIIT | Cero's shown. Timeline also leads on review sentiment (100% vs 75%) and monetization model (free vs free with in-app purchases). Interval Timer for HIIT | Cero's advantage is update cadence (every 3 days vs every 22 months) and ratings volume (437 vs 9). On price, rating, in-app purchases and device support there is nothing between them.

Both are free to download. Timeline sells 1 one-off in-app purchase and Interval Timer for HIIT | Cero sells 2 in-app purchases, starting at $2.99 per month. Whichever you choose, the download price is not the number that matters.

On the App Store both sit at effectively the same score — 4.6 for Timeline against 4.7 for Interval Timer for HIIT | Cero. That said, the two scores are not equally well evidenced: Interval Timer for HIIT | Cero has 437 ratings behind it against 9, so its average is the more settled of the two. Written reviews are what separate them: 100% of Timeline's written reviews are positive against 75% of Interval Timer for HIIT | Cero's.

Timeline ships an update every 22 months, Interval Timer for HIIT | Cero every 3 days. The most recent releases landed on October 24, 2026 and October 29, 2026 respectively.

## The numbers

| Metric | Timeline | Interval Timer for HIIT | Cero |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [4.6 (9 ratings)](https://appshunter.io/ios/app/timeline-interval-timer/id1234080761/reviews) | **[4.7 (437 ratings)](https://appshunter.io/ios/app/interval-timer-for-hiit-cero/id1256319392/reviews)** |
| Number of ratings | 9 | **437** |
| Positive reviews | **100.0% of reviews** | 74.6% of reviews |
| In-app purchases | Yes | Yes |
| Ads | **No** | Yes |
| Update frequency | Every 22 months | **Every 3 days** |
| Monetization | **Free** | Free with in-app purchases |
| Size | 9 MB | 45 MB |
| Requires iOS | **12.0** | 16.0 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, Apple Watch |
| Age rating | 4+ | 4+ |
| Developer | [Fly Your Vision B.V.](https://appshunter.io/developer/1022537687) | [Flawless Studio LLC](https://appshunter.io/developer/1228312508) |

## What reviewers say

### Timeline

[App page](https://appshunter.io/ios/app/timeline-interval-timer/id1234080761)

This app provides a highly customizable interval timer for various activities, including fitness, exercise, and productivity. Create and manage timer sequences with intuitive gestures, utilize ready-made templates, and share your routines with others. Enjoy spoken prompts and motivational messages to stay on track.

**Highlights:** Flexible interval timer design, Intuitive gesture-based timer creation, Ready-made schemes and templates, Manage and arrange timers by category, Share timers with friends or clients, Spoken timers and motivational messages, Continuous alarm option

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

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Timeline Interval Timer Pro | $4.99 | one-time |


### Interval Timer for HIIT | Cero

[App page](https://appshunter.io/ios/app/interval-timer-for-hiit-cero/id1256319392)

This interval timer app enhances various workouts like HIIT, Tabata, and yoga with intuitive design and customizable timer modes. Create and save custom intervals, track calorie expenditure, and sync settings across devices, including Apple Watch.

**Highlights:** Customizable interval timers, Simple and advanced timer modes, Create and save multiple workout settings, Apple Watch compatibility with heart monitor, Automatic calorie tracking to Apple Health, Cross-device sync

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

**In-app purchases (2)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Cero Pro Monthly | $2.99 | per month |
| Cero Pro | $14.99 | one-time |

**What reviewers like**

- 👍 Simple and straightforward
- 👍 Very practical and customizable
- 👍 Great for HIIT and Tabata
- 👍 Clear design and easy to use
- 👍 Good value, no subscription

**What reviewers complain about**

- 🔋 Drains battery
- 🎶 Music playback interrupted
- ⚠️ Ads interrupt timers
- 🔊 Weak or non-functional sound/haptics
- 🔄 Forced updates

**Reported bugs**

- App runs in background draining battery
- Rotation broke after update
- Apple workout app overrides Cero app on Apple Watch
- Interval signals too weak or not working

**Requested features**

- Ability to group timers
- Option to add warm-up and cool-down features
- Ability to type numbers for time adjustment
- Timer sounds through headphones or interrupting music
- Ability to change exercise names


## Frequently asked questions

### Is Timeline free?

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

### Is Interval Timer for HIIT | Cero free?

Interval Timer for HIIT | Cero is free to download, with in-app purchases available.

### Which has better reviews, Timeline or Interval Timer for HIIT | Cero?

Interval Timer for HIIT | Cero is rated higher. Timeline averages 4.6 out of 5 from 9 ratings, while Interval Timer for HIIT | Cero averages 4.7 from 437 ratings.

### Do Timeline or Interval Timer for HIIT | Cero have ads?

Interval Timer for HIIT | Cero shows ads; Timeline does not.

### Which is updated more often, Timeline or Interval Timer for HIIT | Cero?

Timeline ships an update every 22 months, and Interval Timer for HIIT | Cero every 3 days. Most recently, Timeline was updated on October 24, 2026 and Interval Timer for HIIT | Cero on October 29, 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.*