Local Cookie n/apx

Measured with JS, saved as Cookie. Delete Cookie

Server Cookie n/apx

Cookie value read by PHP at last HTTP Request. (The Cookie is not available at the initial Request.)

User Agent

Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)

At the initial request, the server can know about the browser only through the User Agent string. If this should not be used, tailor-made content can only be served after the Cookie is set at the browser and submitted to the server on the second HTTP request.
One option would be to check on the server, whether the cookie is set, if not, redirect to a small page, which sets the cookie and then requests the page again. Will probably kill Search Engine Indexability though...

Conditional Div <650

Only shown when window size is smaller than 650px. Content is generated on the server, window resizes will not load/reload the content, but only toggle visibility.

Conditional Div >650

Only shown when window size is larger than 650px. Content is generated on the server, window resizes will not load/reload the content, but only toggle visibility.

Conditional Image