# HIIT Interval Timer | Cero vs TimerFlex

The clearest difference is rating: HIIT Interval Timer | Cero at 4.7 against TimerFlex's 3.0. HIIT Interval Timer | Cero also leads on ratings volume (435 vs 2) and update cadence (every 3 days vs weekly). TimerFlex's advantage is review sentiment (100% vs 75%). On price, ads, in-app purchases and monetization model there is nothing between them.

Both are free to download. HIIT Interval Timer | Cero sells 1 one-off in-app purchase and TimerFlex sells 7 in-app purchases, starting at $1.49 per 7 days. Whichever you choose, the download price is not the number that matters.

HIIT Interval Timer | Cero holds the better App Store score, 4.7 against 3.0. That said, the two scores are not equally well evidenced: HIIT Interval Timer | Cero has 435 ratings behind it against 2, so its average is the more settled of the two. Written reviews complicate that: 75% of HIIT Interval Timer | Cero's written reviews are positive against 100% of TimerFlex's, so the app with the better star average is not the one people write more warmly about.

HIIT Interval Timer | Cero ships an update every 3 days, TimerFlex weekly. The most recent releases landed on September 25, 2026 and September 21, 2026 respectively.

## The numbers

| Metric | HIIT Interval Timer | Cero | TimerFlex |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.7 (435 ratings)](https://appshunter.io/ios/app/hiit-interval-timer-cero/id1256319392/reviews)** | [3.0 (2 ratings)](https://appshunter.io/ios/app/timerflex-wod-interval-timer/id6738749653/reviews) |
| Number of ratings | **435** | 2 |
| Positive reviews | 74.6% of reviews | **100.0% of reviews** |
| In-app purchases | Yes | Yes |
| Ads | Yes | Yes |
| Update frequency | **Every 3 days** | Weekly |
| Monetization | Free with in-app purchases | Free with in-app purchases |
| Size | 42 MB | 79 MB |
| Requires iOS | **16.0** | 26.0 |
| Devices | iPhone, iPad, Apple Watch | iPhone, iPad, Apple Watch |
| Age rating | 4+ | 12+ |
| Developer | [Flawless Studio LLC](https://appshunter.io/developer/1228312508) | [Plainworks Teknoloji Limited Sirketi](https://appshunter.io/developer/1782187835) |

## What reviewers say

### 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 (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Cero Pro | $3.99 | 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


### TimerFlex

[App page](https://appshunter.io/ios/app/timerflex-wod-interval-timer/id6738749653)

This app uses AI to instantly create custom workout timers from whiteboard photos or text descriptions. It offers various pre-built formats, real-time heart rate tracking, and detailed workout history. Advanced features like Apple Watch sync and unlimited AI generation are available with a subscription.

**Highlights:** AI workout generation from photos/text, Apple Watch sync with haptic cues, Real-time heart rate and calorie tracking, 5 purpose-built workout formats (For Time, AMRAP, EMOM, Tabata, Custom), 1RM calculator, Voice coach and audio cues, Workout history and monthly stats

**Features:** Apple Watch app

**In-app purchases (7)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Weekly subscription | $1.49 | per 7 days |
| TimerFlex Monthly | $3.49 | per month |
| 3 Months subscription | $8.49 | per 3 months |
| TimerFlex Annual Offer | $12.99 | per year |
| TimerFlex Annual | $24.99 | per year |
| Ad-Free | $0.99 | one-time |
| TimerFlex Lifetime | $34.99 | one-time |


## Frequently asked questions

### Is HIIT Interval Timer | Cero free?

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

### Is TimerFlex free?

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

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

HIIT Interval Timer | Cero is rated higher. HIIT Interval Timer | Cero averages 4.7 out of 5 from 435 ratings, while TimerFlex averages 3.0 from 2 ratings.

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

Both HIIT Interval Timer | Cero and TimerFlex show ads.

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

HIIT Interval Timer | Cero ships an update every 3 days, and TimerFlex weekly. Most recently, HIIT Interval Timer | Cero was updated on September 25, 2026 and TimerFlex on September 21, 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.*