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Crossref Metadata Search vs PoetryDB

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

APICrossref Metadata SearchNEW—PoetryDBNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
Authnonenone
CORSyesyes
HTTPSyesyes
Card requirednono
Commercial useyesunclear
Data licenseOpen Crossref metadata (much is CC0)Unverified (public-domain poetry; project is MIT-licensed)
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Rate limit5 requests/second, 1 concurrent (public pool, per X-Rate-Limit headers)Unpublished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 PoetryDB: common questions

Which is more reliable, Crossref Metadata Search or PoetryDB?

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

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

Can I call Crossref Metadata Search and PoetryDB from the browser?

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

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