How to set up a proxy in Mozilla Firefox: step-by-step guide

Before you start

Firefox can use the Windows system proxy, but for precise setup it is better to set the proxy directly in the browser. This changes only Firefox and does not affect Chrome, Edge, messengers, or other programs. If you want a quick refresher on the difference between HTTP, HTTPS, and SOCKS5, open the proxy types guide.

• If you need a stable address for everyday work, you can buy proxies, and free proxies are suitable for testing. For manual selection, also open the proxy list.
• For websites, an HTTP/HTTPS proxy is suitable. For apps and DNS through proxy, SOCKS5 is often the better choice.
• Open the IP check before setup and remember your regular address.
• If the proxy has a username and password, Firefox will ask for them on the first connection.

Cookies and saved files

Before changing IP, clear Firefox cookies and cache. For a full check, delete files for the entire period; if you need to stay signed in on other sites, delete records only for the selected domain.

1. Open Settings → Privacy & Security.
2. For a full cleanup, open history management or site files, choose the period, and delete cookies together with cache.
3. For one site, use site files management, find the domain, and remove only its records.

In Firefox, first choose the cleanup period: for a full check, all time is usually easier.

Select cookies and cache, then delete them before enabling the new IP.

For one site, find its domain and delete only the files connected with it.

Secure DNS

Firefox can enable DNS over HTTPS separately from system settings. When checking a proxy, it helps to know where DNS requests go: through the regular connection, protected DNS, or SOCKS5.

1. Open Privacy & Security and find DNS over HTTPS settings.
2. If you are checking a regular HTTP/HTTPS proxy, temporarily disable DNS over HTTPS or choose a mode you understand.
3. If you are setting up SOCKS5, enable DNS through SOCKS in Firefox network settings.

Open the Secure DNS, DNSCrypt, or DNS over HTTPS block and choose a clear mode for testing.

Connection modes

Firefox network settings are at the bottom of General. In one window, choose a mode: disable proxy, use system settings, automatic detection, a PAC file URL, or enter the address manually.

• No proxy disables proxy for Firefox completely.
• Use system proxy settings takes the address from Windows.
• For automatic setup, choose automatic detection for the network or enter the PAC file URL.
• For a regular IP:PORT, choose Manual proxy configuration.

No proxy mode disables proxy in Firefox only.

To use Windows settings, choose system proxy settings.

Choose automatic proxy detection for the network or the automatic configuration URL mode, paste the PAC file address, and click OK.

HTTP and HTTPS

If you use an HTTP/HTTPS proxy, fill in HTTP Proxy and HTTPS Proxy. For one address, you can enable using this proxy for HTTPS. It is convenient to compare the difference between HTTP, HTTPS, and SOCKS5 in the extended knowledge base.

1. In HTTP Proxy, enter the IP address or domain, and the port next to it.
2. If the same server should work for HTTPS, enable the option to also use this proxy for HTTPS or fill in HTTPS Proxy separately.
3. Leave SOCKS empty if you do not use a SOCKS proxy.
4. Click OK and open a new tab for checking.

For HTTP/HTTPS, enable manual setup, fill in HTTP Proxy and port, enable HTTPS if needed, add exclusions, and check the DNS mode.

SOCKS5 and DNS

Firefox has separate fields for SOCKS5. A key benefit of Firefox is that it can send DNS requests through SOCKS5, so the site does not see DNS requests from your regular connection.

1. In SOCKS Host, enter the proxy address, and the port next to it.
2. Choose SOCKS v5 if the server supports version 5.
3. Enable Proxy DNS when using SOCKS v5.
4. Leave HTTP Proxy and HTTPS Proxy empty if you want all Firefox traffic to go through SOCKS5.

For SOCKS5, fill in SOCKS Host, choose SOCKS v5, enable DNS through SOCKS, and check DNS over HTTPS mode if it is enabled.

Check and disable

After setup, check the external IP and DNS. For SOCKS5, it is especially important to verify that DNS through proxy is enabled if your task needs it.

1. Open the IP check in Firefox.
2. Enter the proxy username and password if Firefox asks for access.
3. In No proxy for, add addresses that should open directly: localhost, 127.0.0.1, *.example.com.
4. If the IP did not change, check that No proxy or Use system proxy settings is not selected.
5. To disable the proxy, return to Network Settings and choose No proxy or Use system proxy settings.