Verify SNI is configured correctly for TLS virtual hosting.
The SNI Tester checks that Server Name Indication (SNI) is working as expected. SNI sends the intended hostname in the TLS ClientHello so a server can choose the right certificate when hosting multiple domains on one IP. The tester connects with different SNI values and reports which certificate the server returns. Use it to confirm that each hostname gets the correct cert, to debug virtual-host TLS issues, and to ensure SNI is not being stripped (e.g. by old proxies). Essential for multi-tenant or multi-domain TLS setups.
Extension in the TLS ClientHello that sends the hostname the client is trying to reach; the server uses it to select a certificate.
When one IP hosts many domains, the server needs the hostname to pick the right certificate before the handshake completes.
Server may serve a default or wrong cert, causing name mismatch errors; fix client SNI or server virtual host config.
Modern clients do; very old clients (e.g. IE on XP) may not; the tester uses SNI to show what the server does.
Yes. The tester lets you set the SNI value; use it to verify certs for different hostnames on the same server.