How exactly does Windows apply your proxy settings?

For the Windows proxy settings:
1. Can applications simply choose not to use the settings you have defined? For instance, can Firefox decide to route its packets directly to the router instead of through the proxy that you have defined in your Windows settings?
2. Do the proxy settings apply to only browser traffic or will it apply system-wide (e.g. SMTP, IMAP, FTP, etc)
3. Does Windows apply your proxy settings based on the process name (e.g. chrome.exe, firefox.exe) or the protocol? In other words, will the operating system only force HTTP/HTTPS traffic through the proxy?

I'm trying to understand the technical details of exactly how the Windows proxy works. I've heard that Firefox can choose not to use your proxy settings.

Samuria said:

You shouldn't be using a proxy the only time you get a proxy is if your av uses one to check network traffic. You can sometimes get a proxy is malware creates one

I understand that malware sometimes utilizes the Windows proxy settings. I'm not saying this has happened to me. I'm just trying to understand how the Windows proxy settings operate. If I have a proxy server on my network and I put its IP into the Windows proxy settings, how does Windows use this information? Like in my original post, is it routing all traffic through the proxy? Only certain protocols? Can applications choose whether or not to go through the proxy?

How exactly does Windows apply your proxy settings?

A bit complicated

1. System-wide proxy settings (netsh winhttp...)
...they influence OS & metro apps; cannot be used against strictly authenticated proxy
2. IE settings
...it can be different config, they accept proxy autoconfig & authentication
3. Usable browsers (waterfox, palemoon etc)
...independent configuration; they have several options (no proxy, same as IE, their own settings)
4. Other programs
...it depends, they can use any method or combination of choices

The system proxy settings simply provide an option that browsers and other Internet applications can use or not use according to how they are configured. Applications usually provide several options, such as direct access, using the system proxy settings, or their own configuration. You could have several browsers and other applications, each with their own proxy settings. Default configuration of applications is often to use the system proxy settings. That way they will usually work without any other configuration.