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Crossref Metadata Search vs Wolne Lektury

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

APICrossref Metadata SearchNEW—Wolne LekturyNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
Authnonenone
CORSyesyes
HTTPSyesyes
Card requirednono
Commercial useyesunclear
Data licenseOpen Crossref metadata (much is CC0)Works are public domain or on free/Creative Commons licenses (per WolneLektury); API terms not formally stated
Free tierFree, no key (public pool)Free — limits not published
Rate limit5 requests/second, 1 concurrent (public pool, per X-Rate-Limit headers)Unpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

Crossref Metadata Search vs Wolne Lektury: common questions

Which is more reliable, Crossref Metadata Search or Wolne Lektury?

On our scheduled checks, Wolne Lektury leads on measured uptime — Crossref Metadata Search at —% versus Wolne Lektury 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 Crossref Metadata Search and Wolne Lektury need an API key?

Neither needs a paid key — Crossref Metadata Search is callable with no signup, and Wolne Lektury is callable with no signup. Both are quick to prototype with; rate limits still apply.

Can I call Crossref Metadata Search and Wolne Lektury from the browser?

Yes — both Crossref Metadata Search and Wolne Lektury 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 Crossref Metadata Search and Wolne Lektury free for commercial use?

Crossref Metadata Search allows commercial use on its free tier, and Wolne Lektury 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.