Comparison

Timeline vs HIIT Interval Timer | Cero

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

Timeline

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
Read full description

Timeline is the most flexible interval timer. Ideal for fitness, running, exercise, productivity and more. It gives you intuitive, powerful and practical controls to run timer sequences or to create your own routines. • FLEXIBLE BY DESIGN Whether it is for sports such as fitness, running, cycling, high-intensity training, tabata, circuit training, yoga and more. Or if you want to time your daily routines, stay productive, stay focused or need to clock your tasks. Timeline has got you covered. • CREATE TIMERS USING INTUITIVE GESTURES You can create your own sequences of timers quickly using intuitive gestures. There are no difficult menus and options to go through. Just swipe, pinch, pan, tap and group to build any sequence you can imagine. What you see is what you get. You can always edit your timers, even after you have started playing them. • READY-TO-USE SCHEMES AND TEMPLATES Start right away with ready-made schemes and templates. Get into running with 56 weeks worth of training schemes to run from 0 to 5 km up to a full marathon. Use or create your own templates as the starting point for your custom timers. You can import ready-made timers, build your own on your computer or open them directly from websites. • MANAGE AND ARRANGE YOUR WAY Whether you want to arrange your timers per category, or want to separate your clients from your personal timers. Timeline gives you the freedom to manage and arrange your timers the way you want. Creating, moving or copying timers and folders are all only a few taps away. • SHARE WITH FRIENDS OR CLIENTS Share any number of timers and folders at once with your friends or clients. You can also publish them on your website so your audience can directly open them in the Timeline app. • SPOKEN TIMERS AND MOTIVATION IN YOUR LANGUAGE Have your timers and countdown spoken out loud in your own language. You don't have to look at your screen and can keep your device locked or in your pocket. Spoken motivational messages support you through your extensive workouts and sessions. • CONTINUOUS ALARM OPTION TO NEVER MISS A MOMENT Sometimes it is critical to know the end of your timers. You don't need to stay with your device all the time. Just turn on the continuous alarm. It works like your alarm clock and will pause your timer until you have confirmed the alarm. • PRACTICAL FEATURES YOU WILL LOVE Timeline is a premium-quality interval timer app. You can play your own music through Timeline or via your preferred music app. Timeline works fully in the background and can alert you with sounds, vibrations and speech. Run it in the foreground and it will keep your screen turned on if you want. Resume timers where you previously left off. Choose from different color themes. Get personal assistance from the developer. Plus more practical features to ensure you'll enjoy using Timeline. • UPGRADE TO TIMELINE PRO You can use all main features of Timeline completely free. However, to create more than 5 timelines or to share your timers, please upgrade to Timeline Pro with a one-time purchase. You thereby also support an individual developer. Timeline is designed to be your flexible interval training timer. Download Timeline now and start achieving your personal goals.

About

HIIT Interval Timer | Cero

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
Read full description

Build an interval workout around the way you train. Cero is a flexible interval timer for HIIT, Tabata, circuit training, WODs and HYROX preparation. Set up a quick work/rest timer or program each interval in detail. Distinct colors, large controls and reliable cues keep you focused on the session instead of the clock. BUILD YOUR SESSION • Set work, recovery, sets, warm-up and cool-down. • Create advanced workouts with custom intervals, colors, icons and intensity levels. • Save, duplicate and reorder timers. • Share timers by file or QR code. • Review completed sessions in workout history. STAY IN THE WORKOUT • Follow compatible sessions with Live Activities and Dynamic Island. • Start saved or recent timers from Home Screen widgets. • Use Siri and Shortcuts to start, pause, resume and stop a timer. • Put Gym Display on a larger screen or mirrored TV. • Choose a default song or assign music to individual intervals. • Customize sounds, voice cues, vibrations and background alerts. TRAIN BY HEART RATE Adaptive HR can extend recovery until you reach your target heart rate, then guide hard efforts with low and high alerts. Pair a Bluetooth heart-rate monitor with iPhone or train with heart-rate data from Apple Watch. COUNTDOWN AND STOPWATCH The built-in countdown and lap stopwatch cover warm-ups, station changes, rest periods and race-day practice. Stopwatch sessions continue after you close and reopen the app. ON APPLE WATCH Run saved workouts from your wrist, follow heart rate and use the standalone countdown and stopwatch. Cero can save completed workouts and estimated calories to Apple Health. Automatic iCloud backups help protect saved timers and custom intervals. Useful for HIIT, Tabata, circuits, EMOM-style workouts, boxing rounds, strength and conditioning, indoor cycling, running intervals and hybrid race preparation. Feedback and suggestions: hi@flawless.studio Terms of Use (EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

Screenshots

Timeline4 screens
HIIT Interval Timer | Cero4 screens

Verdict

The call

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.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

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.

ReceptionRating · Positive reviews · Number of ratings

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.

UpkeepUpdate frequency

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.

Scorecard6 real differences · 4 level
Timeline versus HIIT Interval Timer | Cero: the parameters behind the verdict, then further details
ParameterTimelineHIIT Interval Timer | Cero
PriceFreeFree
Rating4.6 (9 ratings)4.7 (435 ratings) — better
Positive reviews100.0% of reviews — better74.6% of reviews
Number of ratings9435 — better
Update frequencyEvery 22 monthsEvery 3 days — better
AdsNo — betterYes
In-app purchasesYesYes
MonetizationFree — betterFree with in-app purchases
DevicesiPhone, iPad, iPodiPhone, iPad, Apple Watch
Requires iOS12.0 — better16.0
Further details — not scored
Size9 MB43 MB
Age rating4+4+
DeveloperFly Your Vision B.V.Flawless Studio LLC

Customer experience

Timeline

All ratings9 ratings
Positive88.9%
Neutral0.0%
Negative11.1%
Written reviews2 reviews
Positive100.0%
Neutral0.0%
Negative0.0%

HIIT Interval Timer | Cero

All ratings435 ratings
Positive92.9%
Neutral3.9%
Negative3.2%
Written reviews59 reviews
Positive74.6%
Neutral10.2%
Negative15.3%

Bugs and requests

Timeline

Not enough reviews yet to summarise bugs or requests.

HIIT Interval Timer | Cero

Reported bugs

4 issues
  • 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

5 requests
  • 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

In-app purchases

1 purchases

Timeline

One-time1
  • Timeline Interval Timer Pro$4.99
2 purchases

HIIT Interval Timer | Cero

Subscriptions1
  • Cero Pro Monthly7 Days trial$2.991 Month
One-time1
  • Cero Pro$14.99

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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