Precautions

From Retro Windows wiki

You shouldn't run Windows XP as your main computer any more. Put it on a spare computer or in a virtual machine. Use USB drives or optical media to transfer files instead of risking downloading from the internet on Windows XP.

Microsoft has not supported Windows XP for over seven years now (April 8 2014) so it has a large security problem. Installing Service Pack 3, an up to date antivirus and firewall may provide a small amount of protection, but there are multiple unpatched security holes. Browsing on Windows XP is therefore done at your own risk. Many Malware developers are specifically targeting Windows XP systems.

Using Windows XP for web browsing is not recommended for purposes such as online banking or other purposes that require security. It is recommended that any computer using it doesn't have any important files or personal information that could be lost to ransomware or hacking. Windows XP does not natively support TLS 1.2, TLS 1.3 and newer protocols which makes accessing secure (HTTPS) sites difficult (see Internet Access), but browsers like Mypal and New Moon include their own libraries for accessing secure sites. XPbrowsers.com used to be designed not to use HTTPS so older web browsers could access it before expiring in mid to late 2022 (but Miraheze requires https for this wiki). If you can’t download a browser try downloading Firefox first or transfer a setup file from a computer with a newer operating system. Mypal web browser's website can be accessed from IE6.

It is recommended that modern operating systems such as Windows 10 should be used instead albeit on a more modern computer (around circa 2006 maybe). An alternative to upgrading Windows is to install Linux or use a Mac, Phone, Tablet or Chromebook. A dual boot system or putting Windows XP in a virtual machine is also recommended. Businesses should not be connecting Windows XP to the internet at all, and any systems with legacy hardware or software should be fully air gapped. Use of Windows XP and other unsupported software in a business may even violate data protection laws in your country. Of course Windows XP is still supported by hobbyists and advanced users. This site will continue to provide information about Windows XP.

Browsers for Windows XP don’t have the latest rendering engines as they have not been ported to XP. Any website that requires a browser newer than Firefox version 52 or Chromium 49 will likely not work. User agent spoofing might work for some sites. New Moon and Mypal support HTML5 video. You may need to change your user agent settings to emulate a newer OS to get some websites to load. Advanced features like Web Assembly, WebGL and EME video are not supported well. There are Chinese web browsers that have ported newer versions of Chromium to XP but have problem with non Chinese TLS certificates and languages.

Many Windows XP era computers have processors that don’t support the SSE2 instruction set. These include Pentium III and Athlon XP. Modern browsers need these features so new hardware is recommended. Firefox 45ESR is the last major browser that can run on non SSE2 processors. There are builds of New Moon that can work too.