How to set up a proxy in Firefox

Setup guide · Last revised Oct 20, 2026

Open Connection Settings

1. Open Firefox’s settings: the menu button (three lines), then Settings, or type about:preferences in the address bar.
2. Type proxy in Find in Settings.
3. Click Configure proxy under Proxy settings. In older versions, such as Firefox 140, the button is Settings… under Network Settings (Firefox’s own interface text). The Connection Settings dialog opens.

Fill it in

Mozilla’s page sums up the HTTPS box: “If the same proxy name and port number are used for all protocols, check Also use this proxy for HTTPS.” Firefox never sends localhost through the proxy: “Connections to localhost, 127.0.0.1/8, and ::1 are never proxied” (Firefox’s dialog text). The other choices, No proxy and Use system proxy settings, turn it off or hand it back to the computer’s setting (Windows, Mac).

The login

The dialog has no field for a username or a password. Firefox asks for them in a sign-in box when the proxy requests them; enter the proxy login from your provider’s dashboard, which is often not your account’s email and password. If you let Firefox save it, the dialog’s Do not prompt for authentication if password is saved box logs you in without asking; Firefox’s own description of it: “You will be prompted if authentication fails.” A login that keeps coming back is a 407 from the proxy.

SOCKS5

With no login field in the dialog, a SOCKS5 proxy that needs a password has nowhere to take it. Use the provider’s HTTP port, or SOCKS5 with IP allowlisting (username and password vs IP whitelist). With SOCKS5, tick Proxy DNS when using SOCKS v5: otherwise your own network looks up every site you visit (DNS leaks through a proxy).

Keep your everyday Firefox as it is

The setting belongs to the Firefox profile, so a second profile can use the proxy while your usual one does not. Type about:profiles in the address bar, choose Create a New Profile, open it with Launch profile in new browser, and set the proxy there. The profile also keeps the job’s cookies and logins apart from yours.

Check that it works

Open https://api.ipify.org: it should show the proxy’s address. https://ipinfo.io/country shows its country. Your other profile, or another browser, shows your own address beside it.

Reload it a few times. If the address changes on every reload, the gateway rotates on each request, and sites that keep you signed in may sign you out between pages. For browsing, use a sticky session, which keeps one address for a set time; providers usually set it with a session name in the username: sticky sessions and rotation.

What a browser costs in traffic

A browser loads every image, script, video and ad on a page, and keeps background connections open (sync, updates, extensions). On a plan billed by the GB, that is all traffic you pay for. A separate profile with no extensions and no sync, used only for the job, keeps it down. What a GB costs today: residential proxy prices.

Next

How to test a proxy. For pages that fail: proxy errors, by who sends them.