Comparison

Flip Timer & stopwatch vs Acid Interval

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

Head to head
About

Flip Timer & stopwatch

This app offers a full-screen digital timer with a unique flip animation to visualize time progression. It also includes a stopwatch for tracking activities like workouts, study sessions, and work. Customize reminder sounds and background audio for an immersive experience.

Highlights
  • Full-screen digital timer
  • Flip animation for time visualization
  • Countdown timer
  • Stopwatch functionality
  • Customizable reminder sounds
  • Background sound options
  • Keep screen on for progress viewing
Features
Read full description

Flip Timer, A full-screen digital timer. Countdown, flip animation allows you to feel the passage of time; Stopwatch, record your sport, fitness, work, study and so on. - Swipe up or slide down to set the countdown duration - you can set up timed reminder sound - Focus on the work, you can set the background sound, so you immersed them. - Keep the screen on, You can view the progress of time at any time

About

Acid Interval

This focus timer offers a visually unique approach to deep work, moving away from traditional interfaces. It provides customizable timers and engaging visual feedback to help users stay on task, even with the screen off. The app prioritizes a distraction-free experience with no account or data syncing required.

Highlights
  • Unique visual interface
  • Customizable timer intervals
  • Engaging animation mechanisms
  • Screen-off notifications
  • No account or data sync
  • Phone lock compatibility
Read full description

A focus timer worth looking at. Most focus timers look like a spreadsheet with a countdown in it. This one is built the other way round. A single enormous numeral, bleeding off the edge of a field of acid green. Behind it, a mechanism that moves in time with the clock and never drifts. Rings that bounce, breathe, ripple inward, or pass momentum down a Newton's cradle. A square whose perimeter burns like a fuse, four seconds a side, for box breathing. When you start a session the whole field inverts to black and the numbers light up like something switched on behind them. Tap anywhere to start. Swipe to change the color. You never have to open a menu. 25/5, 50/10, 90/20, or count up. The classic pomodoro, longer ultradian blocks, or open-ended flow when you don't want a deadline. Timed properly. Built on timestamps, not ticks. Lock your phone, switch apps, come back: it is exactly where it should be. It tells you when you are done, even with the screen off. No account. No sync. No data leaves your phone. ACID INTERVAL PRO One payment unlocks all eight mechanisms, all ten colorways, and custom interval lengths. The timer itself is free and always will be.

Screenshots

Flip Timer & stopwatch4 screens
Acid Interval4 screens

Verdict

The call

The clearest difference is ads: Acid Interval at none against Flip Timer & stopwatch's shown. Acid Interval also leads on rating (5.0 vs 4.6) and update cadence (every 2 weeks vs every 3 months). Flip Timer & stopwatch's advantage is ratings volume (7.6K vs 1) and device support (3 vs 1). On price, in-app purchases and monetization model 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. Flip Timer & stopwatch sells 3 one-off in-app purchases and Acid Interval sells 1 one-off in-app purchase. Whichever you choose, the download price is not the number that matters.

ReceptionRating · Positive reviews · Number of ratings

Acid Interval holds the better App Store score, 5.0 against 4.6. That said, the two scores are not equally well evidenced: Flip Timer & stopwatch has 7.6K ratings behind it against 1, so its average is the more settled of the two.

UpkeepUpdate frequency

Flip Timer & stopwatch ships an update every 3 months, Acid Interval every 2 weeks. The most recent releases landed on October 24, 2026 and October 22, 2026 respectively.

Scorecard6 real differences · 4 level
Flip Timer & stopwatch versus Acid Interval: the parameters behind the verdict, then further details
ParameterFlip Timer & stopwatchAcid Interval
PriceFreeFree
Rating4.6 (7.6K ratings)5.0 (1 ratings) — better
Positive reviews68.6% of reviews—
Number of ratings7.6K — better1
Update frequencyEvery 3 monthsEvery 2 weeks — better
AdsYesNo — better
In-app purchasesYesYes
MonetizationFree with in-app purchasesFreemium
DevicesiPhone, iPad, iPod — betteriPhone
Requires iOS15.0 — better17.0
Further details — not scored
Size46 MB1 MB
Age rating4+4+
Developer俐 马Preston Carr

Customer experience

Flip Timer & stopwatch

All ratings7,580 ratings
Positive89.1%
Neutral4.8%
Negative6.1%
Written reviews280 reviews
Positive68.6%
Neutral8.2%
Negative23.2%

Acid Interval

All ratings1 ratings
Positive100.0%
Neutral0.0%
Negative0.0%

Bugs and requests

Flip Timer & stopwatch

Reported bugs

3 issues
  • Timer randomly stops counting down
  • Unable to stop/reset timer once started
  • Ads prevent user from interacting with timer

Requested features

4 requests
  • Add option to set timer in hours/minutes/seconds
  • Implement repeat/loop functionality for timer
  • Allow custom alarm/notification sounds
  • Improve landscape mode support

Acid Interval

Not enough reviews yet to summarise bugs or requests.

In-app purchases

3 purchases

Flip Timer & stopwatch

One-time3
  • Remove Ads$0.99
  • All the skins$0.99
  • Pro Version$1.99
1 purchases

Acid Interval

One-time1
  • Acid Interval Pro$2.99

Questions

Is Flip Timer & stopwatch free?
Flip Timer & stopwatch is free to download, with in-app purchases available.
Is Acid Interval free?
Acid Interval is free to download, with in-app purchases available.
Which has better reviews, Flip Timer & stopwatch or Acid Interval?
Acid Interval is rated higher. Flip Timer & stopwatch averages 4.6 out of 5 from 7.6K ratings, while Acid Interval averages 5.0 from 1 ratings.
Do Flip Timer & stopwatch or Acid Interval have ads?
Flip Timer & stopwatch shows ads; Acid Interval does not.
Which is updated more often, Flip Timer & stopwatch or Acid Interval?
Flip Timer & stopwatch ships an update every 3 months, and Acid Interval every 2 weeks. Most recently, Flip Timer & stopwatch was updated on October 24, 2026 and Acid Interval on October 22, 2026.

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