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TETR.IO vs xkcd

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

APITETR.IOHEALTHY96xkcdHEALTHY98
Uptime · 30d
Uptime · 90d100%100%
Uptime · 30d100%100%
P50 · ms357164
P95 · ms9061070
Authnonenone
CORSyesno
HTTPSyesyes
Card requirednono
Commercial useunclearno
Data licenseUnverifiedCC BY-NC 2.5
Free tierFree, no API keyFree, no API key
Rate limitHonor server-provided cache expiry (~60s); docs require cachingUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

TETR.IO vs xkcd: common questions

Which is more reliable, TETR.IO or xkcd?

Both are neck-and-neck — TETR.IO and xkcd each measure 100% uptime over 90 days on our probe schedule. Reliability here is verified from our own scheduled checks; use the 30-day bars above to see which has been steadier lately.

Which is faster, TETR.IO or xkcd?

xkcd has the lower median latency in our checks — TETR.IO responds in 357 ms versus xkcd at 164 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 TETR.IO and xkcd need an API key?

Neither needs a paid key — TETR.IO is callable with no signup, and xkcd is callable with no signup. Both are quick to prototype with; rate limits still apply.

Can I call TETR.IO and xkcd from the browser?

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

Are TETR.IO and xkcd free for commercial use?

TETR.IO has unclear commercial terms, and xkcd is personal/non-commercial only. 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.