SSL/TLS handshake errors & how to fix them
Transport Layer Security (TLS), the successor to the now-deprecated Secure Sockets Layer (SSL), is a security protocol that encrypts data exchanged between two points on the internet (e.g., a web server and a browser). It also authenticates a website's identity.
This process begins with a TLS handshake, a critical negotiation that determines how the client and server will securely communicate. If the handshake fails, the connection cannot be established.
Common TLS handshake errors include connection failures, timeouts, and mismatches between supported protocol versions. These can block users from accessing your website or service securely.
Updated on: August 18, 2025
TLS is essential for protecting sensitive customer data and business-critical information. It provides encryption capabilities required by most data privacy regulations. Meanwhile, HTTPS, which indicates that a website uses the TLS/SSL protocol, is an SEO ranking factor.
However, purchasing and installing an SSL/TLS certificate is just the first step. The server and client must also complete the handshake successfully for a secure connection to be established. You must also address the underlying causes of TLS errors, such as TLS handshake failure or timeouts.
A TLS/SSL handshake error prevents a browser, like Google Chrome, Mozilla Firefox, and others, from establishing a secure connection with a website or online service. It can be detrimental to business because hackers may intercept or manipulate sensitive data such as personal information, login credentials, and credit card numbers. The ensuing security breach could tarnish your reputation, diminish customer trust, lead to loss of business, and cause compliance issues. An SSL handshake failure is one of the most common types of these connection breakdowns and requires immediate attention.
Handshake failures can occur on either the client or server side and are often tied to configuration issues, expired or invalid certificates, unsupported TLS versions, or incompatible cipher suites.
Let's take an in-depth look at the most common causes, how to address them, and how to prevent these errors proactively.
What is a TLS handshake failure?
An "SSL handshake failed" message indicates that an error has occurred when the server and the client try to establish a secure connection. The TLS handshake is a multi-step process that involves protocol negotiation, certificate exchange, and key generation to create a secure session. This failure means the secure session could not be initiated, preventing secure data transfer.
What causes a TLS handshake failed error and how to fix it?
TLS errors have various causes, which require different fixes. Some originate from the client side—such as outdated browsers or incorrect settings, while others stem from the server, like invalid certificates or misconfigured TLS protocols. Identifying the root cause is key to restoring a secure connection. The most common ones include:
Client-side causes of a TLS handshake error
- Incorrect system time: A TLS error happens when the system clock is different from the actual time. Since an SSL/TLS certificate specifies a validity time frame, a mismatch in date/time can lead to a handshake failure. The user can fix this error by correcting the system time and date.
- Browser error: A browser misconfiguration or plugin may cause an SSL/TLS handshake error. The user can switch to a different browser to find out if a TLS handshake failure is caused by the browser's configuration. If the site still fails to connect, then disable all plugins and try again. Keeping your web browser updated also helps maintain compatibility with modern TLS protocols and certificates. Clear your cache and cookies, as these may interfere with the connection handshake. Also try disabling browser extensions temporarily to rule out conflicts.
- Man-in-the-middle (MITM) attack: Besides malicious activities, this error can occur when a connection is interrupted by a network component like a firewall. If the disruption occurs on the client side, the user may adjust their VPN or antivirus settings to address the issue. Some proxy servers and content filters can also interfere with certificate validation and cause a tls handshake failed error. Temporarily disabling proxy settings may help isolate the cause.
Server-side causes of a TLS handshake error
- Protocol mismatch: A TLS handshake failure occurs when the client and the server don't mutually support a TLS version, e.g., the browser supports TLS 1.0 or TLS 1.1 while the server supports TLS 1.3. In this case, the user should upgrade their browser to work with the latest TLS version. Ensuring both sides use a compatible version of TLS is essential for successful handshakes.
- Cipher suite incompatibility: An error occurs when the client and the server don't have a compatible cipher suite, i.e., they can't agree on how to encrypt and decrypt data. Since TLS 1.3 has deprecated outdated ciphers, it's best to have the client upgrade to the latest TLS version.
- SNI-enabled servers: Server name indication (SNI) can lead to TLS errors when an older client/device doesn't support SNI, or the server has incorrect SNI configurations. You can fix this error by ensuring accurate server SNI configurations and that the SSL/TLS certificate corresponds to the hostnames.
- Certificate issues: Revoked, inactive, or expired certificates can cause TLS errors. A handshake failure may also occur when the hostname doesn't match the common name (CN) in the certificate. Incomplete certificate chains or missing intermediate certificates can also trigger an SSL handshake error. You can prevent these issues by purchasing your TLS certificates from a reputable certificate authority (CA), like Sectigo, and establishing a robust digital certificate management process.
- Misconfigured firewall rules: Firewalls or network security policies that block TLS ports (e.g., port 443) or interfere with handshake traffic can stop the connection from completing. Check the server’s security groups or firewall settings for possible blocks.
What is a TLS handshake timeout?
This TLS error occurs when the handshake process takes longer than the predetermined duration. The connection attempt is considered unsuccessful and the handshake is aborted.
What causes a TLS handshake timeout?
A TLS handshake timeout occurs when the client and server fail to complete the handshake process within a defined period. While a handshake failure often signals a clear misconfiguration or incompatibility, a timeout typically points to delays, unresponsive systems, or disruptions introduced along the connection path. These issues can stem from either the client or server side—and resolving them requires identifying where the process is being delayed or blocked.
Common causes of TLS handshake timeouts include:
- Network latency and slow network connections delaying the transmission of handshake messages
- Misconfigured routers or outdated firmware interfering with secure connections and contribute to handshake timeouts
- A heavy server load or resource constraint increasing the time required to complete the handshake
- Intermediate network devices, such as firewalls, load balancers, proxies, or deep packet inspection tools, disrupting or delaying the handshake process
- A server that is unreachable, unavailable, or experiencing downtime
- Client-side performance issues, including outdated operating systems, browsers, or slow hardware delaying the client’s part of the handshake
- DNS resolution issues, such as slow or misconfigured DNS servers, delaying locating the server’s IP address
- Large certificate chains or improperly configured SSL/TLS certificates extending the time needed to validate and complete the handshake
How to fix TLS handshake timeout errors:
TLS handshake timeouts are often symptoms of deeper performance, configuration, or compatibility issues on either the client or server side. To effectively resolve them, you must pinpoint the underlying cause and apply targeted fixes. Below are practical solutions that address the most common sources of TLS handshake timeout errors:
Optimize server performance by allocating sufficient resources (CPU, memory, bandwidth) to handle inbound connections efficiently.
Implement load balancing across multiple servers to avoid bottlenecks or overloading a single machine.
Verify that TLS versions and cipher suites are compatible between client and server and aligned with current best practices.
Update server software, TLS libraries, and SSL configurations regularly to benefit from the latest performance improvements and security patches. Even minor errors in server config can cause handshake delays or failures.
Monitor network latency and DNS resolution times to detect delays introduced by third-party services or infrastructure.
Use diagnostic tools to trace where the handshake process stalls or exceeds the timeout threshold.
How to prevent TLS/SSL handshake errors
Proactively preventing TLS/SSL handshake errors helps ensure users and customers can access your website or online services without disruptions. It also helps deliver a seamless experience to promote operational efficiency, minimize costly downtime, and build trust with visitors.
Since TLS handshake failures can stem from a variety of causes prevention requires a multi-layered strategy that includes proper configuration, consistent monitoring, and disciplined certificate lifecycle management.
Configure and maintain your server to prevent handshake errors:
Support the latest TLS protocols (e.g., TLS 1.2 and 1.3) and strong cipher suites.
Verify that the certificate chain is complete and properly installed.
Ensure the server’s SNI configuration matches the certificate’s CN and hostnames.
Balance CPU, memory, and bandwidth to promptly handle handshake requests.
Keep server and operating system software updated to avoid compatibility and performance issues.
Strengthen operational visibility and user experience:
Monitor network conditions to identify and resolve latency early.
Avoid overloading individual servers through load balancing or scaling.
Implement error-handling logic to inform users of connection issues gracefully.
Use logging workflows to aid in diagnosing and fixing handshake failures. Documented troubleshooting procedures can accelerate response times and help prevent recurring misconfigurations.
Test across multiple browsers and devices to ensure broad compatibility.
Most importantly, maintain active and accurate SSL/TLS certificates from a trusted CA. For example, Sectigo offers various types of SSL/TLS certificates (e.g., extended validation, organization validation, domain validation, wildcard, and multi-domain). These certificates meet the highest standards with 256-bit encryption, the strongest encryption available for web connections.
But purchasing TLS certificates is just the first step. To prevent outages caused by expired or mismanaged certificates, you need airtight certificate lifecycle managemen to prevent expired, inactive, or revoked certificates from causing TLS errors. The best way to ensure nothing falls through the cracks is to automate your certificate lifecycle workflows with a robust certificate management platform.
Sectigo's Certificate Manager (SCM) is a CA-agnostic, universal platform that helps enterprises discover, consolidate, and manage all digital certificates in one place. Start your free trial to see how you can get a bird's-eye view of your certificate inventory, streamline workflows, and minimize TLS errors.
Prevent TLS/SSL Handshake Errors with Sectigo
Reliable, secure connections are essential to earning user trust and maintaining seamless digital experiences. Staying ahead means having the right infrastructure in place to support evolving security requirements and manage certificates with precision at scale.
Sectigo's Certificate Manager (SCM) is a CA-agnostic, universal platform that helps enterprises discover, consolidate, and manage all digital certificates in one place.Start your free trial to see how you can get a bird's-eye view of your certificate inventory, streamline workflows, and minimize TLS errors.