How to Fix PR_END_OF_FILE_ERROR in Firefox: Solving HTTPS Connection Issues

The Error Message

You're mid-scroll when Firefox suddenly hits a wall. Instead of the site you wanted, you're greeted by a "Secure Connection Failed" screen and a cryptic error code:

Secure Connection Failed

An error occurred during a connection to example.com. PR_END_OF_FILE_ERROR

- The page you are trying to view cannot be shown because the authenticity of the received data could not be verified.
- Please contact the website owners to inform them of this problem.

What is PR_END_OF_FILE_ERROR?

Essentially, PR_END_OF_FILE_ERROR means Firefox reached out to a server via HTTPS and expected to finish a secure SSL/TLS handshake, but the connection dropped unexpectedly. The browser reached the "end of the stream" while it was still waiting for security credentials.

Think of it as a phone call where the other person hangs up while you're still saying hello. In 99% of cases, the problem is on your end—usually a piece of software on your computer or network is intercepting the traffic and fumbling the secure connection.

Step-by-Step Fixes

1. Check Your VPN or Proxy Settings

VPNs like NordVPN or ExpressVPN and local proxies are the usual suspects. If a VPN tunnel is unstable or a proxy doesn't recognize the modern cipher suites Firefox uses, it will kill the connection mid-handshake.

Test without the VPN: Turn off your VPN software and refresh the page. If the site loads, your VPN provider might be using an outdated protocol or a congested server node.
Adjust Network Settings:

Open Firefox Settings > General.
- Scroll to Network Settings and click Settings....
- Toggle the option to No proxy.
- Restart the browser and try again.

2. Disable Antivirus "HTTPS Scanning"

Security suites like ESET, Avast, or Bitdefender often use "Web Shields." They perform a Man-in-the-Middle (MitM) operation, decrypting your traffic to scan for malware before passing it to Firefox. If the antivirus doesn't support TLS 1.3 or uses a certificate Firefox doesn't trust, it triggers the PR_END_OF_FILE_ERROR.

To isolate this:

Temporarily disable your antivirus's web protection for 5 minutes.
If the site loads, go into your antivirus settings and look for "Scan SSL," "Enable HTTPS scanning," or "Filter HTTPS traffic." Disable that specific feature for Firefox.

3. Create a Clean Firefox Profile

A corrupted certificate database (cert9.db) can make Firefox reject perfectly valid handshakes. Rather than digging through your AppData folders, it's easier to test with a fresh profile.

Type about:profiles in the address bar and hit Enter.
Select Create a New Profile and name it "Troubleshooting."
Find the new profile in the list and click Launch profile in new browser.

Does the error vanish? If so, your main profile is the problem. You can use the "Refresh Firefox" tool in about:support to reset your settings without losing your bookmarks.

4. Disable DNS over HTTPS (DoH)

While DoH improves privacy, it can conflict with ISP filters or local firewalls. This tension sometimes leads to interrupted connections.

Open Settings and search for "DNS."
Under Network Settings, click Settings....
Switch Enable DNS over HTTPS to "Off," or try a different provider like NextDNS if you were using Cloudflare.

5. Reset SSL Configuration in about:config

If you've ever tweaked Firefox for "hardened" security, you might have disabled the very cipher suites the server requires.

Type about:config and click "Accept the Risk."
Search for security.tls.version.max. It should be 4 (representing TLS 1.3).
Search for security.tls.version.min. It should be 3 (representing TLS 1.2).
If either shows as "modified," right-click and select Reset.

Verification

Once you've applied a fix, confirm the connection is actually healthy:

Clear your cache via Privacy & Security > Cookies and Site Data.
Restart Firefox entirely.
Hit F12 to open Web Developer Tools and go to the Security tab.
Ensure the connection shows TLS 1.3 and a 128-bit or 256-bit encryption strength.

Troubleshooting Tips

The Single-Site Rule: If the error only happens on one domain, the server might be misconfigured. Use SSLLabs to see if the site has a failing grade.
Office Firewalls: Corporate networks often block specific TLS fingerprints. If you're at work, your IT department's firewall might be the one hanging up the call.
Clock Drift: Check your system clock. If your computer thinks it's 2022, the security handshake will fail instantly because certificates will appear expired or not yet valid.