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Chempirical API vs CycleCalcs API

Two free Science & Math APIs compared on access, reliability and developer ratings, using data from our daily health checks.

The verdict

  • Choose Chempirical API if its data fits your use case better; on access and reliability it's level with CycleCalcs API.
  • Choose CycleCalcs API if its data fits your use case better; on access and reliability it's level with Chempirical API.

Side by side

Chempirical APICycleCalcs API
What it doesChemical compounds with physical data, reactions and substructure search.Interpreted astronomy: sun and moon times, moon phases, planets, eclipses, seasons.
ProviderChempiricalCycleCalcs
API keyNot neededNot needed
HTTPSYesYes
CORS (browser calls)YesYes
Status todayOnline · 533 msOnline · 714 ms
Uptime (30 days)UpUp
Developer ratingNot rated yetNot rated yet
PriceFree / free tierFree / free tier
Chempirical docs ↗CycleCalcs docs ↗

About each API

Chempirical logoChempirical API

Chemical compounds with physical data, reactions and substructure search.

Free read-only JSON API for 48,000 compounds, reactions, Antoine constants and azeotropes: search, identifiers, physical data, structure images and reaction scaling.

Strengths

  • No API key needed
  • Callable from the browser (CORS)
  • HTTPS

Ratings, reviews and FAQ →

CycleCalcs logoCycleCalcs API

Interpreted astronomy: sun and moon times, moon phases, planets, eclipses, seasons.

Interpreted astronomy over HTTP: ask for the Moon and get 'Waning Gibbous, 95% lit, sets at 06:14', with every number behind it one field away. Version 2 is 31 endpoints, free and computed live; version 1 stays frozen.

Strengths

  • No API key needed
  • Callable from the browser (CORS)
  • HTTPS

Ratings, reviews and FAQ →

How to choose between them

  • Prototyping or a tutorial? Pick the one that needs no API key (both qualify).
  • Calling from a web page? You need CORS. Otherwise route requests through your own server or a serverless function.
  • Going to production? Favour HTTPS, a strong uptime record and a provider with clear rate limits and terms. Check each API's docs before you commit.
  • Still unsure? Both are free to try: send one request to each and compare the data you get back.

Chempirical vs CycleCalcs FAQ

Do Chempirical API and CycleCalcs API need an API key?

Neither needs an API key; you can call both straight away.

More comparisons

Chempirical API alternatives · CycleCalcs API alternatives · best Science & Math APIs