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REST Countries vs Open Library

Same instrument, two spec sheets — measured, not claimed.

APIREST CountriesHEALTHY—Open LibraryHEALTHY—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
Authnonenone
CORSyesyes
HTTPSyesyes
Card requirednono
Commercial useyesunclear
Data licenseMPL-2.0Mixed — mostly open
Free tierUnlimitedUnlimited within courtesy limits
Rate limitNone publishedSoft — identified UA appreciated
In directory since2026-05-022026-05-02
operationalpartialdownno data

REST Countries vs Open Library: common questions

Which is more reliable, REST Countries or Open Library?

On our scheduled checks, Open Library leads on measured uptime — REST Countries at —% versus Open Library at —% over 90 days. These are our own probe results, not provider claims; the uptime bars above show the day-by-day record for both.

Do REST Countries and Open Library need an API key?

Neither needs a paid key — REST Countries is callable with no signup, and Open Library is callable with no signup. Both are quick to prototype with; rate limits still apply.

Can I call REST Countries and Open Library from the browser?

Yes — both REST Countries and Open Library send CORS headers over HTTPS, so front-end code can fetch either directly with no backend proxy. That makes them easy to swap in a client-side app while you compare responses.

Are REST Countries and Open Library free for commercial use?

REST Countries allows commercial use on its free tier, and Open Library has unclear commercial terms. We track service terms and the data license as separate fields — see the Commercial use and Data license rows above, and confirm both before shipping either in a paid product.