Open Library vs Open VSX Registry API

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

Uptime · 30d
Uptime · 90d88.2%100%
Uptime · 30d81.7%100%
P50 · ms1629245
P95 · ms4878693
Authnonenone
CORSyesyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseMixed — mostly openUnverified
Free tierUnlimited within courtesy limitsFree — limits not published
Rate limitSoft — identified UA appreciated10800 req/window · 10799 remaining
In directory since2026-05-022026-07-05
operationalpartialdownno data

Open Library vs Open VSX Registry API: common questions

Which is more reliable, Open Library or Open VSX Registry API?

On our scheduled checks, Open VSX Registry API leads on measured uptime — Open Library at 88.2% versus Open VSX Registry API at 100% 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, Open Library or Open VSX Registry API?

Open VSX Registry API has the lower median latency in our checks — Open Library responds in 1629 ms versus Open VSX Registry API at 245 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 Open Library and Open VSX Registry API need an API key?

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

Can I call Open Library and Open VSX Registry API from the browser?

Yes — both Open Library and Open VSX Registry API 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 Open VSX Registry API free for commercial use?

Open Library has unclear commercial terms, and Open VSX Registry API 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.