6 min read
Ten Health Metrics, Two Platforms
We checked 10 metrics against Apple's and Google's own docs. Every one exists on both. The shapes don't match, and that is the part that costs you.
healthkithealth-connectdata
Blog
Product breakdowns, API deep-dives, and playbooks for builders in health, wellness, and fitness tech.
What is actually in HealthKit
Counted out of Apple's own documentation, not from memory.
7 min read
Your HealthKit Bridge Last Shipped in 2024
The main React Native HealthKit bridge last released in October 2024. Its Android counterpart cut five versions in one week this August.
healthkithealth-connectecosystem
6 min read
'No Data' Means Four Different Things
An empty health read has several causes and only one is 'connect your device'. Here is the order to rule them out before you write that empty state.
healthkithealth-connectarchitecture
6 min read
HRV Is SDNN on iOS and RMSSD on Android
Apple stores heart rate variability as SDNN. Health Connect stores RMSSD. Different statistics, no conversion factor, and one chart that quietly misleads.
healthkithealth-connectdata
6 min read
64 Cumulative, 53 Discrete: Sum or Average
64 HealthKit quantity types state cumulative aggregation, 53 state discrete. Choose wrong and nothing errors, no test fails, and the chart still renders.
healthkitdataarchitecture
6 min read
Nutrition: HealthKit's Biggest Group at 39
Nutrition is HealthKit's largest group with 39 identifiers, ahead of Activity at 37. It is also the group almost nobody fills. Your food database is why.
healthkitnutritiondata
6 min read
Apple's Newest HealthKit Types Are a Roadmap
Apple ships the data type years before most apps ship the feature. The additions since iOS 16 are a public preview of what the platform expects to matter.
healthkitiosecosystem
6 min read
HealthKit's 9 Mobility Types, Barely Used
HealthKit's Mobility group is 9 identifiers the system derives from ordinary walking. No workout to start, no extra hardware, and almost nobody reads them.
healthkitmobilityios
6 min read
The HealthKit Error That Never Fires
HealthKit defines 17 error cases. The authorization-denied one is documented for saving, not reading — which is why an empty read is so hard to debug.
healthkitiosapi
6 min read
58 HealthKit Types Apple Never Explains
58 of HealthKit's 240 identifiers carry zero words of discussion prose, and the median across all 240 is 15 words. What to do when the docs say nothing.
healthkitdatamethodology
7 min read
HealthKit: 127 of 240 Types Are iOS 8.0
HealthKit has 240 type identifiers and 127 of them shipped in iOS 8.0. None is marked deprecated. The full version histogram, and what it costs you.
healthkitiosdeprecation
7 min read
One Field, Three Tries, Two Honest Nulls
Resolving which value enum decodes a HealthKit category type took three attempts. The first resolved 29 of 30 and was wrong in the worst way.
healthkitdatamethodology
Where the two platforms disagree
The places an Apple type and an Android record stop meaning the same thing.
7 min read
Google Fit: The Signal Came in 2024
Google closed Fit API sign-ups on 2024-05-01 and documented support ends in 2026-12. Both confirmed. The first date was the one that mattered.
deprecationecosystemandroid
What the APIs really cost
Approval gates, engineering effort, and the bill your users pay.
6 min read
The Fitness API Cost Your Users Pay
5 of 24 products bill your end user, not you. All five are direct wearable integrations, and the hardware requirement, not your budget, sets your reach.
wearablescostapi
6 min read
Four Fitness APIs Are Free and Expensive
12 of 24 products cost the developer nothing, and four of those are rated high engineering effort. The API price is the smallest term in the integration.
costapiecosystem
6 min read
Four Ways an API Says Contact Sales
4 of 24 products list contact-sales, and their gate text describes four different waits. What to ask for, and what to have ready before the call.
costapiecosystem
6 min read
Integrate Fitness APIs in Risk Order
Three directory columns decide your build order: approval gate, engineering effort, user-side cost. Start the clocks you cannot compress on day one.
architectureapicost
6 min read
12 of 24 Fitness APIs Have an Approval Gate
Half the directory makes you get approved before production, and the gates are six different obstacles. Which ones start clocks you cannot compress.
apiecosystemcompliance
7 min read
6 Confirmed, 7 Reported: Grade Your Dates
We track 13 dated ecosystem changes. Only 6 come from a primary source. A confirmed date is a plan; a reported one is a rumour with a number on it.
ecosystemdeprecationmethodology
What is changing
Dated deprecations, wind-downs, and how to tell a confirmed date from a rumour.
7 min read
How We Verify, and What a Stamp Can't Say
341 pages, 1188 FAQ entries, 283 resolving citations, median stamp age 36 days. What those numbers prove, and the larger thing they do not.
methodologydataecosystem
Everything else
6 min read
The Health App That Never Touches HealthKit
Most health apps read data before they do anything. A whole category skips it — no OAuth, no entitlement, no PHI. Here's when that's the right call.
architecturecomplianceconsumer health
2 min read
Welcome to AIFitnessAPI
Why we're building a hub for the people shipping the next generation of health, wellness, and fitness products — and what you can expect to find here.
announcementshealth techcommunity
3 min read
How to Choose a Fitness API in 2026
A practical framework for evaluating fitness and workout APIs: exercise data, motion tracking, AI coaching, pricing, and the questions that matter.
fitness APIguidesproduct