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MarketAux vs Open Library

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

APIMarketAuxDEAD0Open LibraryHEALTHY73
Uptime · 30d
Uptime · 90d0.0%88.2%
Uptime · 30d0.0%81.7%
P50 · ms—1629
P95 · ms—4878
AuthapiKeynone
CORSnoyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedMixed — mostly open
Free tierFree tier — token requiredUnlimited within courtesy limits
Rate limit100 requests/day on free planSoft — identified UA appreciated
In directory since2026-07-052026-05-02
operationalpartialdownno data

MarketAux vs Open Library: common questions

Which is more reliable, MarketAux or Open Library?

On our scheduled checks, Open Library leads on measured uptime — MarketAux at 0.0% 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.

Do MarketAux and Open Library need an API key?

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

Can I call MarketAux and Open Library from the browser?

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

Are MarketAux and Open Library free for commercial use?

MarketAux 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.