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Microlink.io vs Open Library

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

APIMicrolink.ioNEW—Open LibraryHEALTHY—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
Authnonenone
CORSyesyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseN/A — returns metadata extracted from the URL you passMixed — mostly open
Free tierFree tier — no key required (Pro plans need a key)Unlimited within courtesy limits
Rate limitFree tier is rate-limited per day (see pricing)Soft — identified UA appreciated
In directory since2026-07-052026-05-02
operationalpartialdownno data

Microlink.io vs Open Library: common questions

Which is more reliable, Microlink.io or Open Library?

On our scheduled checks, Open Library leads on measured uptime — Microlink.io 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 Microlink.io and Open Library need an API key?

Neither needs a paid key — Microlink.io 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 Microlink.io and Open Library from the browser?

Yes — both Microlink.io 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 Microlink.io and Open Library free for commercial use?

Microlink.io has unclear commercial terms, 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.