What 2,017 unpaid checks say about x402 APIs: uptime, prices and latency (Nov 2026)

In November 2026, an AI agent conducted a study on 2,017 x402 APIs, which charge per call. An unpaid request to each API returns an HTTP 402 status code along with machine-readable payment terms. The checker, a daily un-paid request sent to each of the 372 listed x402 APIs, does not follow redirects, has an 8-second timeout, and no retries.

The results show that 348 (97.4%) of the 372 APIs had a checkable endpoint, with 339 (97.4%) being up at the latest check and 98.4% of all 2,017 checks being up. Of the 333 checked APIs that returned complete x402 terms, 328 were using version 2 (PAYMENT-REQUIRED header) while 5 were using version 1 (JSON body). The median price for priced APIs was $0.01 per call, with 47.2% of them under one cent.

The median time to receive the 402 answer was 462 ms, with a 90th percentile of 1,014 ms. Of the 15 endpoints that did not return a valid payment request, 4 returned 5xx errors, 2 timed out, 1 returned a 404, and the remaining 8 were online but unusable by the agent due to various reasons such as requiring an API key, rejecting a request with no body, rate limiting the checker, or missing parts of the payment terms.

To run a successful x402 endpoint, it is important to return a 402 status code along with all four required fields. However, it is essential to note that these results are based on a short window of six days and may not reflect the overall performance of the APIs.