I built Caffeine Clock, the caffeine tracker app that I always wanted to exist

r/SideProjectu/MrIndigo12·October 3, 2025

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The Post

Hi guys! I would love to show you Caffeine Clock 2.0, a tracker I made that shows you your caffeine levels now and in the future, helping you have undisrupted sleep by timing your caffeine better. As a guy who drinks a lot of caffeine, I wanted to make a good caffeine tracking app for a long time, since nothing I found at the time was sufficient. I wanted to make an app that would be easy to use, show you exactly when you'd have enough caffeine to not have your sleep disrupted, and could add all the drinks I usually drink, for free. Some highlights: Accurate caffeine algorithm — able to take the absorption rate and a "sipping" duration into account. Comprehensive onboarding supported by studies. Over 200 drinks in the database — or create your own. Fully offline — the data is only on your phone. No login, nothing. Analytics — including average caffeine consumption, streak tracking, drinks breakdown. Localized into five languages. Free, supported by ads with an option to remove them.

Why this launch worked

The launch resonated because it tapped into a common user need for managing caffeine intake and sleep. The detailed explanation of the app's features, particularly its accuracy and user-centric design (like being offline-first), built credibility. Active engagement with the community in the comments further fostered a positive reception and encouraged adoption.

What Worked

Directly addresses a personal pain point ('the caffeine tracking app I always wanted to build'), making it relatable to other users with similar needs.

Highlights strong technical features and user benefits, such as an 'accurate caffeine algorithm', 'comprehensive onboarding', and 'fully offline' functionality, which appeal to tech-savvy users.

Offers a substantial free database of drinks and the ability to create custom ones, lowering the barrier to entry and increasing immediate utility.

Community Response

The offline-first approach is smart. What's your actual weekly retention rate for users who log their first drink?

Akeriant

Cool app. Option to put in height and weight using metric system would be nice.

jer0n1m0

Heyy, thank you! According to my Play Store stats, its around 20-25% usually, closer to 20% mostly. Though that was the old version of the app, for this one, not sure yet. Hopefully better:)

MrIndigo12

For us ADHD folks, it's be neat if you added in some of the common stimulants (Ritalin, Adderall, etc. etc) and their PK curves too.

Nieros

Hah yes, its preselected for the US, I'll put in the option to change it. Thank you!

MrIndigo12