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HOL Registry Broker vs Open Library

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

APIHOL Registry BrokerHEALTHY94Open LibraryHEALTHY73
Uptime · 30d
Uptime · 90d99.02%88.2%
Uptime · 30d100%81.7%
P50 · ms3861629
P95 · ms9134878
AuthapiKeynone
CORSnoyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedMixed — mostly open
Free tierFree tier — API key requiredUnlimited within courtesy limits
Rate limitUnpublishedSoft — identified UA appreciated
In directory since2026-07-052026-05-02
operationalpartialdownno data

HOL Registry Broker vs Open Library: common questions

Which is more reliable, HOL Registry Broker or Open Library?

On our scheduled checks, HOL Registry Broker leads on measured uptime — HOL Registry Broker at 99.02% versus Open Library at 88.2% over 90 days. These are our own probe results, not provider claims; the uptime bars above show the day-by-day record for both.

Which is faster, HOL Registry Broker or Open Library?

HOL Registry Broker has the lower median latency in our checks — HOL Registry Broker responds in 386 ms versus Open Library at 1629 ms (P50). Tail latency (P95) is in the table above; for most workloads the median is the number that shapes how the API feels.

Do HOL Registry Broker and Open Library need an API key?

Open Library needs no key, while HOL Registry Broker requires a free API key. If you want to start calling without signup, reach for Open Library first.

Can I call HOL Registry Broker and Open Library from the browser?

Only Open Library is browser-friendly — it returns CORS headers over HTTPS. HOL Registry Broker needs a server-side call or proxy, so factor that into which one fits a front-end project.

Are HOL Registry Broker and Open Library free for commercial use?

HOL Registry Broker 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.