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If websites stop loading while you use a proxy, first check whether the problem affects one site or every site, and one browser or all browsers. Then compare the affected browser’s proxy settings with the working browser or your device’s settings. A proxy that cannot reach the internet can block websites, but turning off a required work or school proxy may break access or violate your organization’s setup—check with IT before changing managed settings.
1. Find out what is failing
Try the affected website in another browser, then open a different website in the browser that failed. These two checks separate a site-specific problem from a browser, proxy, or network problem. Mozilla recommends trying another browser and checking whether the proxy server can connect to the internet in its Server Not Found troubleshooting guide, last updated July 28, 2026.
- Only one site fails: The cause may be that site, a proxy routing rule or exception, or a policy that applies to that destination. Test another site and note whether the failing address begins with HTTP or HTTPS.
- Several sites fail in one browser, but work in another: Focus on the affected browser’s proxy settings, extensions, security-software permissions, and profile.
- Sites fail in every browser: Check the network connection and proxy reachability rather than treating it as a Firefox-only or Chrome-only problem.
2. Compare the proxy settings
Browsers do not always use the same proxy configuration. Firefox has its own connection settings, so compare them with a browser that works or the system proxy settings. In Firefox, open Settings and find Network Settings or Proxy settings. Mozilla’s guide to Firefox connection settings explains the available choices.
If this is your personal connection and you do not use a proxy—or do not know of one and are checking whether an unintended setting is involved—select No Proxy in Firefox and test again. If the device belongs to work or school, do not remove or change a required proxy without checking with IT. Your organization may manage the proxy address, port, setup script, or certificate.
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Check Windows proxy configuration
Windows can use automatic detection, an organization-provided setup script, or a manually entered server address and port. To inspect these options, open Settings > Network & internet > Proxy. Microsoft documents these controls, including exceptions and VPN-related settings, in its Windows proxy settings guide.
If a setup script or manual address is configured and you do not recognize it, ask the person who manages the device or network to confirm it rather than guessing at a replacement. A Proxy Auto-Configuration (PAC) file can send some destinations directly and others through a proxy; Windows can also have exceptions for particular addresses. That means a setting can work for most sites but fail for selected ones. Do not edit an organization’s script, address, port, or exceptions without approval.
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3. Use the browser error as a clue
An error message narrows the possibilities, but does not prove that the proxy is at fault. Google’s Chrome connection-error guidance describes these common codes:
| Error | What it can indicate | Useful next check |
|---|---|---|
ERR_NAME_NOT_RESOLVED |
The hostname cannot be resolved, or it resolves to a different IP address than expected. | Try another site and confirm the address is spelled correctly. If several sites fail, check network and proxy connectivity. |
ERR_CONNECTION_TIMED_OUT |
The connection took too long; connectivity may be slow, or the page may be busy. | Try a different site and retry after a short wait. If all sites time out, check the network and proxy. |
ERR_CONNECTION_RESET |
The connection was interrupted. | Test another site and browser. If it persists, check browser security software and proxy settings. |
ERR_CONNECTION_REFUSED |
The destination rejected or blocked the connection. | Check whether the failure is limited to one destination; a site or proxy policy may be involved. |
ERR_EMPTY_RESPONSE |
The page sent no data and may be down. | Try the site later and test other destinations before changing proxy settings. |
If HTTPS produces a certificate authority error
Some managed proxies inspect HTTPS traffic and require a certificate installed by the organization. If Chrome reports a certificate authority error on a work or school network, Google says the proxy’s certificate may be missing or uninstalled and recommends contacting the administrator. Do not install a certificate you obtained or were sent without verifying it with IT; Google warns that installing one independently is usually a security risk.
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If only HTTPS sites fail
HTTPS is commonly carried through an HTTP proxy using the CONNECT method, which creates a tunnel to the destination. Not every proxy supports CONNECT, and some restrict it to certain ports. A proxy or PAC policy could therefore allow ordinary HTTP sites while blocking particular HTTPS destinations. The MDN reference for HTTP CONNECT explains the tunnel and its restrictions. For a managed network, ask IT to check the relevant proxy policy rather than trying to bypass it.
4. If the problem is limited to one browser
Make one change at a time and retest the same page, so you can identify what helped. Start with configuration and reversible checks rather than advanced browser preferences.
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- Compare proxy settings. In Firefox, open Settings > Network Settings and compare the selection with the working browser or system. Use No Proxy only when appropriate for a personal connection; verify required managed settings with IT.
- Check security software. If the problem began after a security-software or browser update, check whether the software is blocking the affected browser. For a certificate error, Chrome’s guidance also points to antivirus HTTPS scanning as a possible factor. Do not leave protection disabled after a diagnostic test; restore it afterward.
- Check extensions. Temporarily disable extensions one at a time and retest. In Chrome, an Incognito test can help identify whether an extension is involved, though extension behavior depends on its settings.
- Clear site data when only certain sites fail. Clear cookies and cache for the affected site, then sign in again if needed.
- Check for a captive Wi-Fi portal. On public or guest Wi-Fi, complete the network’s sign-in page before troubleshooting browser proxy settings.
- Update the operating system and browser. An outdated system or browser can contribute to connection or certificate problems.
Mozilla also documents advanced DNS-prefetch and IPv6 troubleshooting. It labels these checks for experienced users and warns that changes in about:config can affect Firefox’s stability, security, and performance. Do not begin by changing advanced preferences; use them only when the simpler checks point to that kind of issue and you understand how to restore the original value.
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5. When to contact IT or the site
- Contact your organization’s IT administrator if the device uses a work or school proxy, setup script, manual server address, port, or HTTPS-inspection certificate you cannot verify. Ask whether the proxy is reachable and whether the failing site or HTTPS tunnel is allowed.
- Contact the site operator or wait and retry if one destination fails in multiple browsers while other websites load normally, especially when the error suggests a refusal or empty response.
- Contact your internet provider or network administrator if all browsers fail across multiple sites and the proxy or network connection is unavailable.
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