How many stores support UCP?

As of live saved checks accessed 8 November 2026, in ARC's directory sample of 11,839 completed HTTP checks, Declared is not measured, Valid 8,761 of 14,137 (62%), Usable 7,940 of 14,137 (56.2%), Returns checkout link 7,501 of 14,137 (53.1%). Live figures (n = 11,839) are re-read from saved checks, each with its own date. Downloads are the dated weekly snapshot 2026-11-06, n = 10,698, so their counts can differ. Missing, failed and unknown checks are outside this count and are not a no. Results change as checks are saved. ARC stops before payment. This sample is not a census of every store on the web.

Completed-check counts

ARC saved checks, accessed 2026-11-08

Declared: Not measuredNot measured/.well-known/ucp answered HTTP 200 with a bodyLive saved checks, accessed 8 November 2026. Not a frozen snapshot.

Valid: 8,761 of 14,137 (62%)MeasuredProfile passed ARC's validationLive saved checks, accessed 8 November 2026. Not a frozen snapshot.

Usable: 7,940 of 14,137 (56.2%)MeasuredThe UCP catalog tool returned the tested productLive saved checks, accessed 8 November 2026. Not a frozen snapshot.

Returns checkout link: 7,501 of 14,137 (53.1%)MeasuredUCP create_cart returned a checkout linkLive saved checks, accessed 8 November 2026. Not a frozen snapshot.

The first sentence uses these four rows. Declared: /.well-known/ucp answered HTTP 200 with a body Valid: Profile passed ARC's validation Usable: The UCP catalog tool returned the tested product Returns checkout link: UCP create_cart returned a checkout link

Live figures (n = 11,839) are re-read from saved checks, each with its own date. Downloads are the dated weekly snapshot 2026-11-06, n = 10,698, so their counts can differ.

The platform note below is the weekly snapshot's checkout-link split. It is a different count from the four stages above.

A missing, failed or unknown check is outside the denominator and is not a no. Results change as new checks are saved. ARC stops before payment. The sample is ARC's directory, not a census of every store on the web.

Every protocol uses the same stages on /protocols/ucp. The frozen files are on /data.

Frequently asked questions

How many stores support UCP?
As of live saved checks accessed 8 November 2026, in ARC's directory sample of 11,839 completed HTTP checks, Declared is not measured, Valid 8,761 of 14,137 (62%), Usable 7,940 of 14,137 (56.2%), Returns checkout link 7,501 of 14,137 (53.1%). Live figures (n = 11,839) are re-read from saved checks, each with its own date. Downloads are the dated weekly snapshot 2026-11-06, n = 10,698, so their counts can differ. Missing, failed and unknown checks are outside this count and are not a no. Results change as checks are saved. ARC stops before payment. This sample is not a census of every store on the web.
Is this every online store?
No. It is ARC's directory sample of completed HTTP checks, not a census of every store on the web. A missing, failed or unknown check is outside the count and is not a no.
Does Declared mean agents can reach checkout?
No. Declared is not measured, Valid 8,761 of 14,137 (62%), Usable 7,940 of 14,137 (56.2%), Returns checkout link 7,501 of 14,137 (53.1%). Live saved checks, accessed 8 November 2026. Not a frozen snapshot. A checkout link is not an order. ARC stops before payment.
Why can this differ from the weekly dataset?
Live figures (n = 11,839) are re-read from saved checks, each with its own date. Downloads are the dated weekly snapshot 2026-11-06, n = 10,698, so their counts can differ. Not measured is not zero.

Related

On ARC

Cite this: ARC, arcreport.ai, accessed 2026-11-03, index snapshot 2026-11-06, CC-BY-4.0. Protocol figures: Live saved checks, accessed 8 November 2026. Not a frozen snapshot. Index browser figures: Snapshot 2026-11-06, 6 November 2026. Platform figures: Live saved checks, accessed 3 November 2026. Not a frozen snapshot.

Every figure is labelled Measured, Inferred or Not measured. Not measured is not zero. A missing result is not a mark against a store. ARC stops before payment.