Hello.
In versions 6.5 and 6.7 we have 2 clients to connect to the vcenter server or ESXi Host:
vSphere web client (Adobe Flash)
vSphere client (HTML5)
vSphere web client (Adobe Flash)
A browser (32bits) with the Adobe Flash player plugin is required.
To use the vSphere Web Client (Flash), enter the URL:
https://ip_address of VC/vsphere-client
vSphere client (HTML5)
A browser that supports HTML5 is required
To use the vSphere Client (HTML5), enter the URL:
vSphere Client - HTML5 (https://FQDN-or-IP-Address-of-VC/UI)
Host Client - HTML5 (https://FQDN-or-IP-Address-of-ESXi-host/UI)
VMware announced in May 2016 that the Legacy C# Client (aka thick client, desktop client, or vSphere Client) will no longer be available with the vSphere 6.5 release
more info in the following link
https://kb.vmware.com/s/article/78589