# Timeline vs HIIT Interval Timer | Cero

The clearest difference is ads: Timeline at none against HIIT Interval Timer | Cero's shown. Timeline also leads on review sentiment (100% vs 75%) and monetization model (free vs free with in-app purchases). HIIT Interval Timer | Cero's advantage is update cadence (every 3 days vs every 22 months) and ratings volume (435 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 HIIT Interval Timer | 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 HIIT Interval Timer | Cero. That said, the two scores are not equally well evidenced: HIIT Interval Timer | Cero has 435 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 HIIT Interval Timer | Cero's.

Timeline ships an update every 22 months, HIIT Interval Timer | Cero every 3 days. The most recent releases landed on September 22, 2026 and October 12, 2026 respectively.

## The numbers

| Metric | Timeline | HIIT Interval Timer | Cero |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [4.6 (9 ratings)](https://appshunter.io/ios/app/timeline-interval-timer/id1234080761/reviews) | **[4.7 (435 ratings)](https://appshunter.io/ios/app/hiit-interval-timer-cero/id1256319392/reviews)** |
| Number of ratings | 9 | **435** |
| 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 | 43 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 |


### HIIT Interval Timer | Cero

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

**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 HIIT Interval Timer | Cero free?

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

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

HIIT Interval Timer | Cero is rated higher. Timeline averages 4.6 out of 5 from 9 ratings, while HIIT Interval Timer | Cero averages 4.7 from 435 ratings.

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

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

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

Timeline ships an update every 22 months, and HIIT Interval Timer | Cero every 3 days. Most recently, Timeline was updated on September 22, 2026 and HIIT Interval Timer | Cero on October 12, 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.*