Firefox holds a special place among proxy users: it is the only major browser with a proxy setting that is completely independent of the system. This means Firefox can exit with a different IP while your system connects normally — tailor-made for testing and multi-identity scenarios.
Step-by-Step Setup
- Open Settingsfrom the Firefox menu.
- General tab: scroll to the very bottom and click the Network Settings > Settings... button.
- "Manual proxy configuration" — select this option.
- Fill it in according to your address type:
- For an HTTP/HTTPS address , enter the IP and port in the "HTTP Proxy" row; tick the "Also use this proxy for HTTPS" box.
- For a SOCKS5 address , fill in the "SOCKS Host" row and select SOCKS v5as the version.
- Press OK — no restart is required.
A Critical Option: "Proxy DNS when using SOCKS v5"
If you are using SOCKS5, be sure to tick this box. When it is unchecked, domain name resolution goes to your own ISP's DNS servers and the sites you visit remain visible — the classic DNS leak. When it is checked, resolution is performed on the proxy side and the leak is closed. This option is the detail that makes Firefox the best browser for privacy-focused proxy use.
Rule-Based Routing with a PAC File
The "Automatic proxy configuration URL" option asks for a PAC (Proxy Auto-Config) file. PAC uses a JavaScript function to define which site goes through which proxy — for example, you can send only certain domains through the proxy and leave the rest of the traffic direct. It is a powerful tool for advanced users.
Exceptions
Addresses you type into the "No proxy for" field (e.g. localhost, 127.0.0.1, *.sirketici.local) bypass the proxy. Handy for your local development servers.
Verification
The routine trio after setup: IP check → DNS test → if needed, WebRTC test. In Firefox it is possible to disable WebRTC completely: about:config , set media.peerconnection.enabled → false. If these three checks are clean, your Firefox identity is entirely on the proxy.
Where to Get an Address?
To try it out, free proxy list; to try SOCKS5, the SOCKS5-filtered view. For continuous use, all of the paid packages are fully compatible with Firefox.