Every antidetect browser runs a proxy check before it opens a profile, and the check is the moment most setup problems surface. AdsPower reports a proxy failure and refuses to start the profile. Multilogin shows "Proxy check failed" or "Proxy is offline" next to the profile. GoLogin, Dolphin Anty, Incogniton, and the rest have their own wording for the same event: the browser tried to reach the world through the proxy you entered and did not get a working exit back.
The vendors' help pages agree on the causes, and they are short lists. AdsPower's names incorrect proxy details, an expired proxy, a VPN or proxy on the device, an internet problem, and a fault at the provider. Multilogin's adds traffic that has run out, interfering antivirus or firewall software, an ISP that blocks the provider, and a timezone mismatch. Two more causes come up constantly in support and are missing from both: an IP-authenticated proxy whose allowlist does not include your current address, and a protocol dropdown that does not match the proxy. Seven reasons, each with a distinct test, and this guide takes them in the order that clears the check fastest.
Your computer
VPN, system proxy, antivirus in the way?
Proxy entry
format, protocol, credentials, allowlist
Provider's exit
alive, traffic left, not blocked by your ISP
Check passes
profile opens with the exit's address
1. The entry is in the wrong format
The single most common cause, and the cheapest to fix. Each browser wants the host in its host field with no scheme, the port in the port field, and the username and password in theirs, with the protocol chosen from a dropdown. AdsPower also accepts a one-line paste in host:port:username:password order; a proxy copied from a dashboard in username:password@host:port order pastes into the wrong fields.
Look for http:// or socks5:// in the host field, a space at the end of any field, a port in the password box, and, for rotating gateways, a username that carries session or country parameters with a typo in them. A username of user-country-de-session-abc123 asks the gateway for a German exit with a fixed session; one letter wrong asks for something that may not exist, and the gateway refuses with a status the browser reports as a failed check.
2. The credentials are expired, or the traffic is gone
A proxy subscription that lapsed, a password that was rotated in the provider's dashboard, or a traffic balance that reached zero all produce a refusal the browser cannot distinguish from a dead proxy. Multilogin's help is specific about the traffic case for its own proxies: a negative figure in the traffic display means the balance is spent, and topping up restores the check. For any provider, open the dashboard: is the plan active, is the password the one in the profile, and is there balance left. Our proxies for antidetect browsers guide covers what a provider's dashboard should show you.
3. A VPN, system proxy, or security product is in the way
AdsPower's first fix after checking the details is to disable any VPN or proxy on the device and reboot. Multilogin's list is longer: antivirus, firewalls, VPNs, and proxy tools can all interfere, and the fix is to uninstall them or allowlist the browser. The mechanism is simple. The antidetect browser opens a connection to the proxy; a VPN reroutes it, a system proxy intercepts it, and a security suite's web shield inspects it, and any of the three can break the handshake that the check depends on.
Disconnect the VPN, switch off any proxy in the operating system's settings (our guide on turning a proxy off covers each system), pause the security product, and run the check again. If it passes, add the browser to the product's exceptions rather than leaving it off.
4. The proxy is IP-authenticated and your address changed
Many proxies can be set to accept connections from an allowlisted address instead of a username and password. It is convenient until the address changes: a new home connection, a VPN that was on when you added the allowlist entry and off now, a laptop that moved networks, or a machine in a different data centre. The proxy then refuses, and the browser reports a failed check with no hint that the cause is the allowlist.
The tell is a proxy that works from one machine or network and not another, or that worked yesterday and fails today after nothing changed in the profile. Check your current address in our IP lookup against the allowlist in the provider's dashboard, and add it. If the browser runs on a machine whose address changes often, credentials are the more reliable method.
5. The protocol does not match
An HTTP proxy checked as SOCKS5, or the reverse, fails every time. The handshake bytes make no sense to the other side. Providers usually list the protocol next to the port in the dashboard, and many offer both on different ports. Change only the dropdown and re-run the check. When the protocol is unknown, our proxy checker tests HTTP, HTTPS, SOCKS4, and SOCKS5 separately for any address and reports which handshakes succeeded.
6. The exit is dead
Proxies go down. Free proxies go down within hours, because thousands of people share each one and the operator has no reason to keep it up; paid exits go down occasionally, and a rotating gateway can have no exit available for a requested country at a given moment. Multilogin's help says to click Check proxy again and to replace the proxy if it stays offline; AdsPower's says to contact the provider once the details and the device have been ruled out.
Test the proxy outside the browser. A dead result in the checker ends the investigation: the exit is gone, and the fix is a different one. A live result means the cause is one of the others on this list. For a profile that must keep the same address for weeks, a fixed-address ISP proxy removes this cause almost entirely; for profiles that need a new address each time, a residential gateway with session control does.
7. Your own network blocks it
Multilogin's help includes a case people forget: the ISP or the local network blocks the proxy provider, and the fix is to try a different connection or a VPN for the leg between you and the proxy. Corporate and campus networks block unusual ports; some ISPs block known proxy ranges. If the check fails on one network and passes on mobile data, the network is the cause, and a proxy on a common port (443 or 8080) has a better chance where port 1080 or a high port is blocked.
The order that clears it fastest
- Test the proxy in an external checker. Dead means reason 6; alive means keep going.
- Re-enter the proxy by hand from the provider's dashboard, checking format and protocol (reasons 1 and 5).
- Confirm the plan is active, the password current, and the balance positive (reason 2).
- Turn off VPN, system proxy, and security products, and re-check (reason 3).
- Compare your current address with the allowlist (reason 4).
- Try another network (reason 7).
Multilogin's help adds two housekeeping items worth doing when nothing else explains a failure: set the device's timezone to sync automatically, since a mismatch can break authentication, and delete the components folder so the app downloads fresh ones. Restarting the application, both vendors note, clears a surprising share of transient failures.
What a profile needs from a proxy
A failed check is the browser protecting the profile, and it is right to. A profile that opens on a dead or shared exit leaks the machine's real address, or arrives on an address with a history that contradicts the identity the profile is meant to hold. The proxy behind a profile has to be alive when the check runs and every time after, keep the same address for as long as the identity needs it, speak the protocol the browser expects with credentials the browser can send, and come from a network the target does not distrust. Public lists fail all four, which is why our posts on free proxies for AdsPower and free proxies for Multilogin spend most of their length on what the failures look like. The antidetect browser proxy setup guide shows the field-by-field entry for each browser once you have a proxy that passes.