ERR_PROXY_CONNECTION_FAILED in Dolphin Anty and Chrome: 7 Causes and How to Identify the Culprit

You open a profile in an anti-detect browser, launch the Facebook Ads dashboard or an Instagram account — and instead of the page, you see a white screen with the message ERR_PROXY_CONNECTION_FAILED or ERR_TUNNEL_CONNECTION_FAILED. This is not uncommon for those managing dozens of accounts through proxies, and most of the time the issue can be resolved in 5–10 minutes if you know where to look for the cause.

What these errors mean in simple terms

Both errors indicate the same thing: the browser was unable to establish a connection to the internet through the specified proxy server. The only difference is at which stage the failure occurs. For an arbitrageur or SMM specialist, this means one thing — the advertising dashboard, Instagram, or TikTok account is currently unavailable, and until the issue is resolved, work comes to a halt.

It is important to understand: this error almost never means the account is banned. It is a problem at the network connection level — the browser is trying to reach the proxy server but either receives no response or is denied access. The causes can be on the proxy side, the target site (Facebook, Instagram, Wildberries), or even in the settings of the anti-detect browser itself.

If the error appears on one specific profile — it is likely related to the proxy assigned to that account. If the error is widespread, occurring on all profiles simultaneously — the problem is likely with the proxy provider or the network through which you are connected to the internet.

What is the difference between PROXY_CONNECTION_FAILED and TUNNEL_CONNECTION_FAILED

These two errors are similar but indicate different stages of failure, and understanding the difference saves time during diagnostics.

Error	When it occurs	Typical cause
ERR_PROXY_CONNECTION_FAILED	The browser cannot even connect to the proxy server	Proxy is down, incorrect port, server overloaded, or blocked by the provider
ERR_TUNNEL_CONNECTION_FAILED	Connection to the proxy exists, but a secure tunnel (HTTPS) to the target site cannot be established	Proxy does not support the CONNECT method, site blocks proxy IP, certificate issues

In simpler terms: PROXY_CONNECTION_FAILED means "could not reach the proxy," while TUNNEL_CONNECTION_FAILED means "reached the proxy, but the connection was interrupted on the way to the site." The second scenario is often encountered when working with HTTPS sites like Facebook or Instagram, where an encrypted connection through a proxy tunnel is required.

7 main causes of the error

In practice, 90% of cases fall into one of the seven scenarios below.

1. The proxy is down or the rental period has expired. The most common reason for those using static datacenter proxies — the port simply stopped responding.
2. Incorrect connection details entered. A typo in the IP, port, username, or password — the browser physically cannot reach the server.
3. The proxy server is overloaded. Too many simultaneous connections on one IP — typical for cheap shared proxies that are used by dozens of clients at the same time.
4. The site's anti-fraud system has blocked the proxy IP. Facebook, Instagram, or Wildberries may have blacklisted a specific IP due to suspicious activity from other users of the same proxy.
5. Protocol incompatibility. You specified SOCKS5 where HTTP/HTTPS is needed, or vice versa — the anti-detect browser is trying to connect using the wrong protocol.
6. Problem on the local network or VPN side. If a VPN or firewall is running on the device that blocks outgoing connections, the proxy will not be able to reach its destination.
7. Failure of the anti-detect browser itself. An outdated version of Dolphin Anty, AdsPower, or GoLogin sometimes incorrectly passes proxy settings to the profile, especially after an update.

How to find the culprit: step-by-step diagnostics

To avoid guessing, follow this checklist — it is structured from the quickest checks to more complex ones.

• Step 1. Check the proxy outside the anti-detect browser — through a third-party proxy checker or command line. If the proxy does not respond there — the problem is definitely not with the browser.
• Step 2. Try the same proxy in regular Chrome using a proxy switcher extension. If the site opened — the problem is in the settings of the anti-detect browser profile.
• Step 3. Open a neutral site (for example, whoer.net) through this proxy, not immediately Facebook. If the neutral site opened, but the target did not, then the proxy IP is blocked by the platform.
• Step 4. Check the logs with the proxy provider — many services show port usage statistics and authorization errors in the personal account.
• Step 5. Temporarily disable VPN, antivirus, and firewall on the device and try connecting again.
• Step 6. Create a test profile in the anti-detect browser from scratch and attach a working proxy to it — if the error does not recur, the problem was in the old profile.

Checking proxies in Dolphin Anty, AdsPower, and GoLogin

Most anti-detect browsers have a built-in proxy check button right in the profile settings — this should be used first.

In Dolphin Anty, open the profile → "Proxy" tab → enter connection details → click the "Check" button. The browser will show the status, geolocation, and response speed. If the test fails, the error will appear even before the profile launches, and you won't have to guess the cause.

In AdsPower, a similar function is located in the profile creation/editing section — "Proxy" field, "Check Proxy" button. The service also highlights if the protocol is specified incorrectly (for example, HTTP is selected, but the provider issued a SOCKS5 port).

In GoLogin and Multilogin, the check works similarly — through a separate connection test button in the profile settings. If the test passes, but ERR_TUNNEL_CONNECTION_FAILED still occurs when launching the browser — this almost always means that the specific site has blocked the IP after successfully connecting to the proxy, meaning the issue is not with the proxy server itself, but with the reputation of its IP on the target platform.

Which type of proxy is less likely to cause such errors

The frequency of ERR_PROXY_CONNECTION_FAILED and ERR_TUNNEL_CONNECTION_FAILED directly depends on the type of proxy you are using. Below is a comparison based on practical observations.

Type of proxy	Connection error frequency	When to use
Datacenter proxies	Average — IPs are often already in the anti-fraud databases of platforms	Parsing, tasks without strict anti-detect checks
Residential proxies	Low — real IPs of providers, rarely on blacklists	Farming Facebook Ads, Instagram, TikTok accounts
Mobile proxies	Minimal — operator IPs with rotation, platform trust is higher	Advertising accounts with high risk of blocking

Cheap shared datacenter proxies often become the source of ERR_TUNNEL_CONNECTION_FAILED because the same IP is used by multiple clients, and as soon as one of them gets banned on the platform, all other users of that same port suffer.

Step-by-step error correction

After you have determined where the problem lies, proceed according to one of the scenarios.

If the proxy itself is at fault (not responding or overloaded):

• Request a new IP from the provider or change the port in your personal account
• Check if the payment or rental period for the proxy has expired
• If it is a shared proxy — switch to a dedicated IP, where the load is only from your tasks

If the protocol is at fault:

• Clarify with the provider which protocol has been issued — HTTP, HTTPS, or SOCKS5
• Correct the connection type in the settings of the anti-detect browser profile
• Resave the profile and restart the browser completely, not just the tab

If the site is blocking:

• Change the IP to a new one from the same pool (for residential and mobile proxies this is done in seconds)
• Clear cookies and cache of the profile before trying to log in again
• Do not access the platform immediately after changing the IP en masse on all profiles simultaneously — this can also look suspicious to the anti-fraud system

If the anti-detect browser is at fault:

• Update Dolphin Anty, AdsPower, or GoLogin to the latest version
• Delete and recreate the profile with the same proxy details
• Check if the system VPN is enabled simultaneously, which conflicts with the proxy inside the profile

How to prevent the error from recurring

To avoid wasting work time on diagnostics every time, it makes sense to establish a prevention system.

• Choose proxies with dedicated IPs per account, rather than shared pools for tasks with a high risk of blocking (Facebook Ads, TikTok Ads)
• Check proxies before launching important advertising dashboards, not just during the initial setup
• Keep a table linking proxies to profiles — this makes it easier to quickly find which specific IP is causing the problem
• Use proxies with automatic IP rotation upon detection of blocking, if the platform you are working with frequently bans IP addresses
• Do not overload one proxy with multiple accounts simultaneously — this is especially critical for SMM agencies managing 20–50 client accounts

Sellers who monitor prices on Wildberries, Ozon, or Avito should separately consider that frequent ERR_TUNNEL_CONNECTION_FAILED during parsing is a signal that the current pool of IPs is already "exposed" and the marketplace recognizes the pattern of requests. In this case, replacing one IP is not as effective as switching to a pool with more frequent rotation.

Conclusion

ERR_PROXY_CONNECTION_FAILED and ERR_TUNNEL_CONNECTION_FAILED are not a death sentence for an account and not a reason to panic. In most cases, the cause is obvious: the proxy stopped responding, the protocol is specified incorrectly, or a specific IP has already been added to the anti-fraud database of the target platform. Step-by-step diagnostics — checking the proxy outside the browser, testing on a neutral site, checking with the built-in tool in Dolphin Anty or AdsPower — allows you to find the culprit in minutes instead of hours of tweaking settings.

If the error occurs regularly specifically on Facebook Ads, Instagram, or TikTok advertising dashboards, it is worth reconsidering the type of proxy being used. For tasks with a high risk of blocking, residential proxies with real IPs of home users are better suited — they are less likely to end up on the platforms' blacklists. For the most risky scenarios, where trust from anti-fraud systems is crucial, arbitrageurs often switch to mobile proxies, which platforms perceive as ordinary users on smartphones.