How to Fix This Site Can’t Be Reached When Using a Proxy

“This site can’t be reached” is Chrome’s generic error page for connection failures. When it appears while using a proxy, the error could originate anywhere in the chain: your device, your local network, the proxy server, or the target website. The accompanying error code (ERR_CONNECTION_TIMED_OUT, ERR_CONNECTION_REFUSED, ERR_NAME_NOT_RESOLVED, etc.) provides the first clue about where the failure occurred.

This guide systematically addresses each variant of this error in the context of proxy usage.

Understanding the Error Variants

ERR_CONNECTION_TIMED_OUT

The browser waited for a response but none arrived. With a proxy, this can mean:

The proxy server is unreachable
The proxy server received your request but the target website did not respond
A firewall is silently dropping packets

ERR_CONNECTION_REFUSED

The proxy server or target website actively refused the connection. This is more definitive than a timeout because the server explicitly sent a TCP RST packet.

ERR_NAME_NOT_RESOLVED

DNS resolution failed. The browser could not translate the hostname (either the proxy hostname or the target hostname) to an IP address.

ERR_PROXY_CONNECTION_FAILED

The browser specifically failed to connect to the configured proxy server. This error is unambiguous: the issue is between your device and the proxy.

ERR_TUNNEL_CONNECTION_FAILED

The HTTPS CONNECT tunnel through the proxy failed. The proxy connected but refused or failed to establish the tunnel to the target.

Diagnostic Workflow

Step 1: Determine If the Issue Is the Proxy or the Target

# Test proxy connectivity
nc -zv proxy.example.com 8080

# Test if the target is accessible directly (without proxy)
curl -s -o /dev/null -w "%{http_code}" https://target-site.com

# Test if the target is accessible through the proxy
curl -s -o /dev/null -w "%{http_code}" -x http://user:pass@proxy:8080 https://target-site.com

If the direct request succeeds but the proxied request fails, the issue is in the proxy chain. If both fail, the target site may be down.

Step 2: Test with a Known-Good Target

curl -x http://user:pass@proxy:8080 https://httpbin.org/ip

If this succeeds, the proxy itself is working. The issue is specific to the target website.

Step 3: Check DNS Resolution

# Resolve the target hostname
nslookup target-site.com

# Resolve the proxy hostname
nslookup proxy.example.com

If either fails, DNS is the problem. Switch to a reliable DNS server (8.8.8.8 or 1.1.1.1).

Fixes by Error Variant

Fix ERR_CONNECTION_TIMED_OUT

Check firewall rules:

Firewalls can silently drop outbound packets to the proxy port, causing timeouts instead of connection refused errors.

# Test if the proxy port is accessible
nc -zv -w 5 proxy.example.com 8080

If this times out, a firewall between you and the proxy is likely blocking the port. Try connecting on port 443 instead, which most firewalls allow.

Increase timeout settings:

# cURL with extended timeout
curl -x http://proxy:8080 --connect-timeout 30 --max-time 120 https://target-site.com

Check proxy server status:

Try a different proxy endpoint:

If your provider has multiple gateways, try an alternative:

curl -x http://user:pass@us-east.proxy.com:8080 https://target-site.com
curl -x http://user:pass@eu-west.proxy.com:8080 https://target-site.com

Fix ERR_CONNECTION_REFUSED

Verify proxy address and port:

The most common cause is an incorrect proxy address or port. Double-check against your provider’s documentation.

Check if the proxy is running:

For self-hosted proxies, verify the proxy process is running:

# Check if something is listening on the expected port
ss -tlnp | grep 8080

Verify IP whitelist:

If your proxy uses IP-based authentication, confirm your current public IP is whitelisted:

curl https://api.ipify.org

Compare this with your provider’s whitelist settings.

Fix ERR_NAME_NOT_RESOLVED

Flush DNS cache:

# macOS
sudo dscacheutil -flushcache && sudo killall -HUP mDNSResponder

# Windows
ipconfig /flushdns

# Linux
sudo systemd-resolve --flush-caches

Change DNS server:

Configure your system to use a public DNS server:

# Test with Google DNS
nslookup target-site.com 8.8.8.8

If this resolves but your default DNS does not, change your DNS settings.

Use proxy IP instead of hostname:

If the proxy hostname does not resolve, use the IP address directly:

curl -x http://user:pass@203.0.113.50:8080 https://target-site.com

Fix ERR_TUNNEL_CONNECTION_FAILED

This error means the proxy CONNECT method failed. Causes include:

Proxy does not support CONNECT:

Some proxies only support HTTP forwarding, not HTTPS tunneling. Verify your proxy supports HTTPS traffic.

Target port is blocked by the proxy:

Some proxies restrict which ports can be tunneled. Standard ports (80, 443) are usually allowed, but non-standard ports may be blocked.

# Test CONNECT to a non-standard port
curl -x http://proxy:8080 https://target-site.com:8443

Proxy authentication failed silently:

Some proxies return a tunnel failure instead of a 407 when authentication fails. Double-check your credentials.

Browser-Specific Fixes

Chrome

Clear browsing data: Navigate to chrome://settings/clearBrowserData and clear cached images and files
Reset proxy settings: Navigate to chrome://settings/ > search for “proxy” > “Open your computer’s proxy settings” and verify the configuration
Disable extensions: Navigate to chrome://extensions/ and disable all extensions, particularly proxy switchers

Firefox

Firefox manages its own proxy settings:

Navigate to Settings > General > Network Settings > Settings
Verify the proxy configuration
Try “No proxy” to confirm the proxy is causing the issue
Try “Use system proxy settings” to inherit OS-level configuration

Safari

Open System Settings > Network
Select your connection > Details > Proxies
Verify or disable proxy settings

Edge

Edge uses the same proxy settings as Chrome (system-level). Follow the Windows or macOS system proxy fixes above.

Advanced Diagnostics

Using Chrome’s Network Log

For persistent issues, capture a Chrome network log:

Navigate to chrome://net-export/
Click “Start Logging to Disk”
Reproduce the error
Stop logging
View the log at https://netlog-viewer.appspot.com/

The log shows the exact point of failure: DNS resolution, TCP connection, TLS handshake, or proxy negotiation.

Using cURL Verbose Output

curl -v -x http://user:pass@proxy:8080 https://target-site.com 2>&1

Look for:

Trying ip:port... followed by a long pause (timeout)
Connected to proxy followed by CONNECT target-site.com:443 (tunnel negotiation)
HTTP/1.1 200 Connection established (successful tunnel)
Any error after the tunnel is established (target-side issue)

Using traceroute

traceroute proxy.example.com

This reveals where packets are being dropped along the network path. If the traceroute stops at a specific hop, a firewall or routing issue exists at that point.

Special Cases

The Site Works for Some Users but Not Others

If colleagues can access the site through the same proxy but you cannot, check:

Your local DNS configuration
Your local firewall rules
Browser-specific proxy settings or extensions
Whether your IP is whitelisted (for IP-authenticated proxies)

The Site Worked Yesterday but Not Today

If access stopped working suddenly:

The proxy provider may have changed endpoints
Your subscription may have expired
The target website may have blocked the proxy IP
Your ISP may have started blocking proxy traffic

Check your provider’s status page and dashboard for any changes.

Only Specific Sites Cannot Be Reached

If most sites work through the proxy but specific ones do not:

The target site may block traffic from your proxy’s IP range
The target site may require a specific geographic location that your proxy does not provide
The proxy may restrict access to certain domains

For sites protected by Cloudflare or similar services, mobile proxies often succeed where data center proxies fail, due to their higher IP trust scores. Check the proxy glossary for definitions of IP trust scoring and related concepts.

Preventing the Error

Monitor proxy health with automated checks every few minutes
Maintain backup proxy endpoints for automatic failover
Keep DNS configured with reliable servers (Google 8.8.8.8 or Cloudflare 1.1.1.1)
Regularly validate your proxy setup with the proxy testing checklist
Document your proxy configuration so you can quickly verify settings when issues arise

Conclusion

“This site can’t be reached” while using a proxy is a generic error with many possible causes. The error code beneath the message (ERR_CONNECTION_TIMED_OUT, ERR_CONNECTION_REFUSED, ERR_NAME_NOT_RESOLVED, ERR_TUNNEL_CONNECTION_FAILED) narrows the diagnosis significantly. Work from the most common causes (incorrect proxy address, blocked port, DNS failure) toward the less common ones (tunnel failures, provider outages). In most cases, the fix is verifying the proxy configuration, checking firewall rules, or resolving DNS issues.