Cloudflare blocking US websites

Put simply, if using a VPN works it means your regular UK IP address is being blocked. You might want to consider calling your UK internet service provider and ask them about the IP address they have assigned you. You may not be the only one being blocked. Also take a look to see if Private Relay on your Mac is active if have a subscription for iCloud services. On your Mac, not Safari, System Settings->Apple Account->iCloud->Private Relay. If it’s one turn it off. You can also test beforehand. In Safari->View->Select Reload and Show IP Address which temporarily bypasses Private Relay and shows your true IP address.

Browse the web in a more secure and private way with iCloud Private Relay - Apple Support

Let us know of the results.

By the way Cloudflare is an American company that provides internet security to many websites. It may well be that Cloudflare doesn't like your IP Address for some reason on any website it is protecting. In either event it is almost a certainty that this is NOT a bug in Safari or macOS 15 Sequoia.

IanMetz wrote:

This has just started happening - access to (some) US websites from the UK is being blocked by Cloudflare.

I can use a VPN to get access by pretending to be based in the US, but that seems ridiculous.

Here's an example screenshot - a perfectly innocent website for a large family restaurant chain, blocked. On Mac and iPhone.

Why?

Is it the unintended consequence of some security feature in iOS and macOS browsing?

What can I do apart from switching a VPN on and off?

https://discussions.apple.com/content/attachment/3780044a-58d5-4bca-9610-2d2176de2fd3

Well if Cloudfare is blocking the website you should report the issue to their support, that isn't an Apple product.

Cloudflare has been blocking a lot of websites recently for reasons known only to them.

This is not a Mac or Apple problem; it's Cloudflare's hosting service. From what I have heard from other website managers who use their services they are becoming increasingly customer-hostile. Getting answers is next to impossible.

Contact the website administrator.

It's possible that your ISP is using carrier-grade NAT or the network that you are connected to is a large privately addressed network behind a NAT router. If this is the case, it is possible that thousands of end-users appear to Cloudflair as coming from the same public-facing IP address. As a result, if even a single one of those users has an infected (bot) IoT device in their home that is performing a denial-of-service attack, then you get blocked as well. The same problem occurs occasionally with Google searches. While ongoing, you can end up either being blocked outright or being required to do CAPTCHA over and over.

You may be able to determine if you are behind a larger NAT network by finding your current WAN IP address and comparing it to the prefixes of carrier-grade NAT or other private IP ranges. Use https://mxtoolbox.com/whatismyip/ to find the IP address of your WAN address. Then compare that against known private IP ranges. If your WAN address is similar to one of the following, you are likely behind some type of large NAT network:

100.64.0.0 to 100.127.255.255

10.0.0.0 to 10.255.255.255

172.16.0.0 to 172.31.255.255

192.168.0.0 to 192.168.255.255

If you find that your ISP is doing this to you, there is not much you can do about it other than: wait until Cloudflair thinks it's safe and lets you in again, change ISPs to one that gives you an actual public-facing IP, or use your VPN.

As my esteemed colleague John Galt points out your issue is indeed with Cloudflare hosting services and you are not alone at all.