What does SSL handshake failed mean?

An “SSL handshake failed” error occurs when a client and server can't complete the initial negotiation process required to establish a secure encrypted connection. This negotiation happens before any data transfer begins and typically completes in under 100 milliseconds.

The SSL handshake is a multi-step exchange in which the client and server agree on security parameters. Both parties negotiate protocol versions, such as TLS 1.2 or TLS 1.3, select compatible cipher suites, and verify SSL certificates to create shared encryption keys.

TLS 1.3 adoption is expected to reach over 60% of HTTPS connections globally by mid-2025, resulting in improved security and performance.

When you see “SSL handshake failed”, this negotiation broke down before completion. The client and server couldn't agree on security settings, verify credentials, or establish trust. Over 90% of these failures are attributed to certificate issues or TLS version mismatches, according to industry guides from Sectigo and SiteGround published in 2024.

Handshake failures fall into several categories.

Common culprits include expired or invalid SSL certificates, incompatible TLS versions between client and server, unsupported cipher suites, incorrect system time settings, and interference from firewalls or antivirus software. Client-side issues, such as outdated browsers, problematic extensions, and network interruptions caused by VPNs or proxies, also trigger these errors.

Understanding SSL handshake failures matters because they directly block secure connections your users need. Browsers like Firefox experience handshake latency increases up to 30 seconds after 10+ certificate re-issues, directly impacting user experience and site accessibility.

What is an SSL handshake?

An SSL handshake is the initial process where a client (like your browser) and server establish a secure encrypted connection before any data transfer begins. It happens in milliseconds but protects all data transmitted over HTTPS connections.

Here's what happens during the handshake: both parties negotiate which protocol version and cipher suite to use, authenticate the server's identity through digital certificates, and generate shared encryption keys. These steps work together to create a secure channel for your data.

What does "SSL handshake failed" mean?

An "SSL handshake failed" error indicates that your browser and the server were unable to complete the negotiation process required to establish a secure connection. The handshake is where both sides agree on protocol versions, select cipher suites, and verify SSL certificates. If any step fails, no secure data transmission happens.

The failure usually comes from certificate problems, TLS version mismatches, or configuration issues.

On the client side, expired certificates, incorrect system time, or outdated browsers commonly trigger this error. On the server side, misconfigured SSL/TLS settings, missing SNI support, or blocked port 443 cause the same issue. When you see this error, it's the system telling you: "We can't agree on how to communicate securely, so we're not connecting at all."

What causes SSL handshake failures?

SSL handshake failures happen when a client and server can't complete the negotiation process needed to establish a secure encrypted connection using SSL/TLS protocols. These failures prevent HTTPS connections. They stem from mismatches in protocol versions, certificate problems, incompatible cipher suites, or network configuration issues.

The most common culprits are expired or invalid SSL certificates, TLS version incompatibilities between client and server, incorrect system time settings, and firewall interference blocking port 443.

Client-side problems include outdated browsers that don't support modern TLS versions, incorrect system clocks that cause certificate validation to fail, and network interruptions from VPN or proxy configurations.

Server-side issues range from misconfigured SSL/TLS settings and expired certificates to a lack of Server Name Indication (SNI) support and servers not listening on the standard HTTPS port 443. When either side can't agree on encryption parameters during the handshake, the connection fails immediately. Users see error messages like "SSL handshake failed" or Cloudflare's error 525.

How to fix SSL handshake failed errors

You fix SSL handshake failed errors by identifying whether the issue stems from your client, the server, or the network, then addressing the specific cause.

1. First, check your system's date and time settings. An incorrect clock causes certificate validation to fail because SSL certificates have specific validity periods. Set your system to sync automatically with internet time servers to prevent this issue.
2. Next, clear your browser's cache and SSL state. Corrupted cached certificates can prevent new handshakes from completing. In Chrome, Firefox, or Edge, clear browsing data and SSL certificates from your security settings, then restart the browser.
3. Then, verify the website's SSL certificate is valid and hasn't expired. Use an online SSL checker tool or your browser's certificate viewer to confirm the certificate matches the domain, hasn't expired, and comes from a trusted authority. Contact the website administrator if you find certificate problems.
4. Update your browser and operating system to support modern TLS versions. Disable outdated protocols, such as TLS 1.0 and 1.1.
5. Disable interfering browser extensions, VPN services, or antivirus software temporarily. These tools sometimes block or modify SSL connections, causing handshake failures. Test the connection with extensions disabled to identify the problem.
6. Check your firewall and network settings to confirm port 443 isn't blocked. Corporate networks and security software often restrict HTTPS ports, preventing SSL handshakes from initiating. Contact your network administrator if you are unable to access port 443.
7. If you manage the server, verify your SSL/TLS configuration supports modern cipher suites and protocols. Run an SSL server test to identify misconfigurations, expired certificates, or missing intermediate certificates that prevent successful handshakes.

If problems persist after taking these steps, try testing the connection from a different network or device. This helps you determine if the issue is local or server-side.

How to prevent SSL handshake errors

You can prevent SSL handshake errors by maintaining valid certificates, supporting modern TLS versions, keeping system clocks accurate, and ensuring proper server configuration.

1. First, verify your SSL certificate is valid and not expired. Check the certificate's expiration date and renew it at least 30 days before it expires to avoid connection failures. Ensure the certificate matches your domain name exactly and is issued by a trusted Certificate Authority, not a self-signed certificate.
2. Next, check that your system clock is accurate on both client and server. SSL handshakes fail when the time difference exceeds a few minutes because certificates include valid-from and valid-until timestamps. Enable automatic time synchronization through NTP to prevent clock drift issues.
3. Then, configure your server to support TLS, avoiding older versions like SSL 2.0 or SSL 3.0.
4. After that, enable compatible cipher suites that match what current browsers support. Remove weak ciphers, such as RC4 or 3DES, from your server configuration and prioritize strong options, like AES-GCM. Your server and client must share at least one common cipher suite for the handshake to succeed.
5. Verify that port 443 is open and accessible through your firewall. Test connectivity from external networks to confirm the port isn't blocked, and check that your server is listening on this port for HTTPS connections.
6. Enable Server Name Indication (SNI) support on your server, especially if you host multiple SSL sites on one IP address. Most modern servers enable SNI by default, but older configurations may need manual updates to handle virtual hosts properly.
7. Finally, update your server software and SSL libraries to the latest stable versions. Outdated OpenSSL versions or web server software can cause handshake failures due to bugs or missing security patches.

Test your SSL configuration regularly with online tools that simulate handshakes from different clients and report potential issues before they affect real users.

How can Gcore help with SSL handshake issues?

The CDN handles SSL termination at edge locations closest to users. This reduces handshake latency and offloads processing from your origin servers. It's a straightforward way to prevent common server-side issues, such as port 443 blocking or SNI misconfiguration, that cause handshake failures.

Gcore's infrastructure automatically negotiates the strongest available encryption while maintaining backward compatibility with older clients.

For troubleshooting, you can monitor certificate expiration dates, TLS version usage, and cipher suite compatibility across your traffic. The platform alerts you before certificates expire and automatically renews them, preventing service disruptions that occur when certificates lapse unexpectedly.

Frequently asked questions

What's the difference between an SSL handshake failure and SSL certificate errors?

An SSL handshake failure occurs when the client and server are unable to complete their initial negotiation to establish a secure connection. SSL certificate errors are different. They are specific problems with the certificate itself, like an expired, invalid, or untrusted certificate.

Here's the key distinction: handshake failures can happen even when you have a valid certificate. Common causes include TLS version mismatches, unsupported cipher suites, incorrect system time, or network issues that block port 443.

How long should an SSL handshake take?

An SSL handshake typically takes 100-250 milliseconds under normal conditions. This timing increases with network latency and the TLS version you're using. TLS 1.3 completes handshakes in one round trip, making it 50-100ms faster than TLS 1.2. Older protocols require additional exchanges, which adds more time.

Can a firewall cause SSL handshake failures?

Yes, firewalls can cause SSL handshake failures. They may block port 443 (the standard HTTPS port) or interfere with SSL/TLS traffic inspection. Deep packet inspection features in some firewalls can also interrupt the handshake process when they attempt to decrypt and analyze encrypted traffic.

What is SNI and why does it matter for SSL handshakes?

SNI (Server Name Indication) is a TLS extension that allows clients to specify the hostname they're connecting to during the SSL handshake. This allows one server to host multiple SSL certificates on a single IP address.

Without SNI, servers can't determine which certificate to present when multiple domains share the same IP. This causes handshake failures for all but the default certificate.

How do I check if my SSL certificate is properly installed?

You can check your SSL certificate installation using online tools or command-line methods. Online SSL checkers, such as Qualys SSL Labs, provide detailed reports on your certificate's configuration and security. For a quick command-line check, run openssl s_client -connect yourdomain.com:443 in your terminal to verify the connection and certificate details.

Your browser's padlock icon offers the simplest verification method. Click it to view certificate details and confirm three key elements: valid dates, correct domain name, and a complete certificate chain. If any of these are missing or incorrect, your SSL certificate isn't properly installed.

What are cipher suites, and how do they affect SSL handshakes?

Cipher suites are sets of cryptographic algorithms that define how a client and server encrypt data during the SSL handshake. They directly affect both connection speed and security strength.

Here's how it works: During the handshake, both parties negotiate which cipher suite they support. If the cipher suites don't match or are too weak, you'll see handshake failures. Worse, the connection might downgrade to less secure encryption, leaving your data vulnerable.

Does SSL handshake failure affect SEO rankings?

Yes, SSL handshake failures indirectly harm SEO rankings by preventing pages from loading. When pages don't load, bounce rates increase, and search engines interpret this as a poor user experience. Search engines can't crawl or index pages that fail to establish secure connections. This effectively removes them from search results.