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What is Server Name Indication (SNI)?

Are you contemplating the SNI meaning? 

Consider SNI as delivering a letter to a housing complex instead of a single-family home. The street address would be sufficient to deliver your letter to the correct recipient in the case of a single-family home. In the apartment complex, you would need the street address and the flat number if you wanted your letter sent to the appropriate recipient.

Multiple web servers contain many domain names, making it difficult to determine which domain a user is attempting to access from their IP address alone. These servers are more like housing complexes than single-family residences.

A powerful HTTPS connection may be prevented or terminated because the server shows the incorrect SSL credential, similar to how a letter cannot be delivered to an address except if the registered owner signs for it.

Do you know the most critical component of a website's security? It's none other than SSL, guaranteeing that your consumers' data will be secured. The two isolated SSL certificates are a "wildcard" and a SNI certificate. However, this article will elaborate on the nitty-gritty factors of SNI. So, let's get started.

What is Server Name Indication (SNI)?

What is SNI?

An encrypted server name indication or encrypted SNI is a TLS protocol’s extension. At the beginning of the TLS handshake, a client or browser can determine the hostname it is attempting to connect to. As a result, the server is able to display numerous certificates utilizing the same IP address as well as port.

Previously, port 443 (https) could not be shared; therefore, any SSL website you hosted required its own IP address on your server. This would not work for one or both of your websites on some servers (like IIS, for instance). By enabling SNI, you can reduce the number of internal and external IP addresses used to serve https-encrypted pages.

What is a Server Name?

SNI really "signifies" the domain name or hostname of a site, which could be unique from the central server’s name handling domain. In essence, hosting numerous domains on a single server is typical; in such a situation, they are called virtual host names.

A server name is nothing more than the identification criterion of a PC. Unless the server hosts just one domain and the server name is identical to the domain name, this name is typically not displayed to end users regarding web servers.

How SNI works?

SNI is a required extension for IPv4, considering that there are only about 4 billion IPs globally, and not all of them are capable of hosting SSL certificates. Hence, protecting several domain names on 1 IP becomes difficult. 

SNI enables website owners to register as many domains and subdomains as they desire without being restricted by the number of existing addresses.

For SNI to operate, both the client and the web server must support it. If they choose not to, the visitor will access a default website; often one hosted on port 443. 

It implies that users who access your website through unencrypted routes, such as links from other websites or Google search results, won't get their traffic encoded. This is usually not a problem, though, as most browsers now automatically reroute to a website's secure version (which typically begins with "HTTPS://").

Why use Server Name Indication (SNI)?

Using a single SSL certificate for all subdomains or different domains on a single IP address saves time and money because it is less expensive and more straightforward to acquire than a certificate for each website address.

The fact that there is only one SSL Certificate Authority (CA) issuing certificates makes SNI hosting more trustworthy. Because there would be numerous CAs involved in traditional wildcard or multi-domain certificates, if one of them were exploited, there might be cybersecurity breaches.

Even if your website receives a lot of traffic, you can still use SNI hosting because a TLS handshake always takes place at the start of an Encrypted connection and has no impact on the performance.

What is TLS?

Data exchanged between applications over the Internet is secured and end-to-end using the cryptographic protocol TLS.

For instance, the padlock icon that appears in web browsers when a secure session is initiated makes it most familiar to consumers when used in secure web browsing. 

Using it for other applications, such as email, file transfers, video/audio conferencing, instant messaging, voice-over IP, and Internet services like DNS and NTP, is also possible and recommended.


What does the SNI extension for TLS do?

SNI, at the commencement of the TLS handshake, allows a client/browser to provide the hostname it is attempting to get associated with. Several certificates can now be shown on the same IP address and port by the server.

What is a hostname? What is a virtual hostname?

A device that connects to a network is known by its hostname. It is a type of domain name when used on the Internet. From the IP address connected to the domain name, both are unique.

A hostname hosted on a server with several other hostnames that do not have its IP address is known as a virtual hostname.

In the same way that virtual reality only occurs in the digital realm and not in the real world, this technology is "virtual" because it lacks a specific hardware server.

Which Browsers Support SNI?

Almost all popular browsers support this feature, and hence, there is no disadvantage in adopting it no matter which browsers your end-users prefer. Here is a quick list for your reference:

  • Google Chrome
  • 5.0.342.1+ on Mac OS X 10.5.7+
  • 6+ on Windows XP and Vista
  • Opera 8.0+ (Support for the TLS protocol must be activated).
  • Safari 2.1+
  • on Mac OS X 10.5.6+
  • on Windows Vista
  • Mozilla Firefox 2.0+

The future of SNI

Despite being established in 2003, SNI is gradually becoming a more widely used technology in the field of security and server name indication SSL certificates. SNI can save time, cash, and frustrations when it comes to protecting your company's or website's online presence, even though not every website owner is obliged to use it.


Server name indication is the best option if you want a more secure and flexible solution to encrypt your website. The SNI SSL certificates provide a lot of security and are less expensive and simpler to maintain than conventional wildcard certificates. They are more adaptable than typical SSL certificates because you can use them on multiple IP addresses.



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February 26, 2024
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