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An unfortunate reality of the modern web is that many websites check your User-Agent string and serve different content (or no content at all) based on what browser they think you are. With our previous UA string, we were getting degraded UIs, "your browser is not supported" pages, network throttling, and outright HTTP 403 errors from many prominent websites.
From: Ladybird Browser Newsletter: This Month in Ladybird — January 2026

A sad case of browser discrimination. I had assumed that with the death of Internet Explorer, such practices had largely faded away. User-Agent (UA) exists to enable graceful degradation, allowing older or less capable browsers to receive simplified content, not to serve as a whitelist that reserves the full web experience for a handful of approved browsers.
When you throttle or block based on UA, you are breaking the ethos of the open web, the very reason the World Wide Web was created in the first place. It is discrimination. From the article, this appears to be fairly common across the websites and services of Big Tech companies, such as Google and Meta. When those same companies also control the lion's share of the browser market, this begins to look uncomfortably close to anti-competitive behavior.