Free tools for health-app builders
10tools that answer a question with a lookup instead of an essay. Every one runs in your browser off this site’s published datasets — the HealthKit identifier set read from Apple’s documentation on 2026-08-28, the HealthKit ↔ Health Connect matrix verified against both vendors, and the API directory. No account, no upload, no server round trip, and nothing invented where the source is silent.
Lookups and generators
Built on the HealthKit identifier dataset and the verified cross-platform matrix.
Which error is this?
Paste an error string and get the matching HKError.Code case in Apple's wording, plus the guide that covers it.
/tools/error-diagnoser
Sum it or average it?
Whether Apple describes a quantity type as cumulative or discrete, with the sentence that says so.
/tools/aggregation-checker
Apple type, Android record
Two-way lookup between HealthKit identifiers and Health Connect records — verified pairs only.
/tools/identifier-translator
HealthKit permission builder
Pick the types your app touches: the Info.plist keys, the toShare/toRead Swift, and the Health Connect record names.
/tools/permission-builder
HealthKit query generator
Pick a quantity type and a window; get the HKStatisticsQuery with the aggregation option Apple's own prose states.
/tools/query-generator
Fitness app stack generator
Answer four questions and get the HealthKit types and APIs that survive them, with the exclusions shown.
/tools/stack-generator
Planners and demos
Decision support for picking a stack, and one demo of the bug that costs the most debugging time.
Which fitness API should I use?
Three questions, a tailored recommendation.
/picker
Fitness API cost planner
The cost structure of your stack: billing models, user-side costs, approval gates, eng effort.
/cost-planner
Compare two fitness APIs side by side
Access structure, user-side cost and approval gates for any two products in the directory.
/compare-apis
Why “today’s steps” is a bug
Interactive: DST days aren't 24 hours, so a fixed UTC window drops or double-counts an hour.
/day-boundaries
What these tools will not do
None of them will fill a gap in the source to look more complete. Where Apple’s wording does not state a type’s aggregation style, the checker says not stated. Where no cross-platform pair has been verified against both vendors’ documentation, the translator says there is no verified counterpart rather than transliterating a name. Where a pasted error matches nothing, the diagnoser says so and links the full reference. A tool that always returns an answer is a tool that sometimes returns a wrong one.
The datasets underneath are published under CC BY 4.0, so you can check any answer yourself or build your own lookup on top — open datasets.
Free tools from AIFitnessAPI. The references behind them: every HealthKit type identifier, every HealthKit error code, and the HealthKit ↔ Health Connect matrix.