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Open Library vs REST Countries

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

APIOpen LibraryHEALTHY—REST CountriesHEALTHY—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
Authnonenone
CORSyesyes
HTTPSyesyes
Card requirednono
Commercial useunclearyes
Data licenseMixed — mostly openMPL-2.0
Free tierUnlimited within courtesy limitsUnlimited
Rate limitSoft — identified UA appreciatedNone published
In directory since2026-05-022026-05-02
operationalpartialdownno data

Open Library vs REST Countries: common questions

Which is more reliable, Open Library or REST Countries?

On our scheduled checks, REST Countries leads on measured uptime — Open Library at —% versus REST Countries 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 Open Library and REST Countries need an API key?

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

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

Yes — both Open Library and REST Countries 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 Open Library and REST Countries free for commercial use?

Open Library has unclear commercial terms, and REST Countries allows commercial use on its free tier. 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.