Using a browser proxy extension alongside the client

Which one wins

Browser proxy settings follow a simple precedence: the extension overrides the system proxy. As long as the extension sits in a profile that points at a proxy, it owns that browser’s traffic entirely, regardless of whether the client has the system proxy switched on.

So when the client is connected but the browser is not proxied, the first thing to check is whether the extension is parked on a direct profile — not whether the client needs a restart.

Three sensible combinations

• Extension set to "system proxy" mode: control goes back to the client, and the browser follows the client’s system-proxy toggle. The low-maintenance option.
• Extension pointed at a fixed 127.0.0.1 port: it talks to the client’s mixed port directly and ignores the system proxy setting. Useful when you want the browser proxied while everything else stays direct.
• Extension in auto-switch mode: domain rules decide what goes through. Remember this is a second layer on top of the client’s own routing rules — the browser decides whether to hand the request to the client at all, and the client then applies its rules. Both layers have to agree.

A port mismatch causes most of the trouble

The port in the extension must be the mixed port the client is actually listening on. Defaults differ between clients — 7890 and 7897 both show up regularly — and if you ever changed it, the extension keeps the old number.

Find the mixed port entry in the client settings and copy the number exactly. A wrong value has a recognisable signature: every page fails with ERR_PROXY_CONNECTION_FAILED or hangs, while every other program on the machine is online.

Keeping the extension while TUN is on

With TUN enabled, traffic is captured at the adapter level. An extension still pointing at 127.0.0.1 just adds a hop; it usually works but buys you nothing. What does break things is an extension pointing at a port that no longer exists — TUN will not rescue the browser from that.

If you use TUN, park the extension on direct or system-proxy mode and let the client handle routing centrally. It is one fewer variable next time something misbehaves.

One change worth knowing about

As Chrome moved to Manifest V3, several long-standing proxy extensions stopped working or were removed from the store, and community-maintained MV3 rebuilds such as ZeroOmega took over. If an old extension suddenly does nothing, check that first before you start editing client configuration.