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Chronicling America vs Micro User Service

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

APIChronicling AmericaNEW—Micro User ServiceNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
AuthnoneapiKey
CORSnoyes
HTTPSyesyes
Card requirednono
Commercial useyesunclear
Data licensePublic domain / no known copyright (Library of Congress)Unverified
Free tierFree — public-domain collection dataFree tier — key may be required
Rate limitLoC throttles heavy crawling (see LoC API policy)Unpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

Chronicling America vs Micro User Service: common questions

Which is more reliable, Chronicling America or Micro User Service?

On our scheduled checks, Micro User Service leads on measured uptime — Chronicling America at —% versus Micro User Service 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 Chronicling America and Micro User Service need an API key?

Chronicling America needs no key, while Micro User Service requires a free API key. If you want to start calling without signup, reach for Chronicling America first.

Can I call Chronicling America and Micro User Service from the browser?

Only Micro User Service is browser-friendly — it returns CORS headers over HTTPS. Chronicling America needs a server-side call or proxy, so factor that into which one fits a front-end project.

Are Chronicling America and Micro User Service free for commercial use?

Chronicling America allows commercial use on its free tier, and Micro User Service 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.