Description
Vivaldi recently became aware that a Japanese site, www.keisan.nta.go.jp, is blocking Vivaldi users from accessing an e-Tax part of the site, demanding they use a different browser.
On Windows, the site is using JS and navigator.userAgentData.brands to decide whether to open the product, or display their "Unsupported browser" dialog, and among Chromium-based browsers the site only accepts two specific browsers identified by the brands "Microsoft Edge" and "Google Chrome". No other Chromium based browser is accepted. (On Mac the situation is apparently that only Safari is accepted)
We have possible reports about a few other sites that may be doing the same.
The only scalable way for a client to work around this issue is to pretend to be one of the accepted browsers, by returning their brand instead of its own.
The scalable solution to the issue is that brand information is never made available to the sites, whether in JS or HTTP headers.
Major vendors are unlikely to be affected by such blocking policies, only smaller vendors will be affected, and such blocking will be a reason for many users to avoid using those browsers. The result is increased market share for the major browsers.
At most general engine information should be provided, and even that could be a serious obstacle for some vendor seeking to create (or fork) a new browser engine.