The web client is a secondary client option for ALM/QC 12 and above. In 12.0/12.01 the client is limited to the Defect and Requirements module while in 12.20 the Test Plan and Test Lab modules are available as well (in Technology Preview and not meant for production). The web client is built into the product and is already available as part of your current ALM/QC installation.

To access, add the below site parameter to your Site Admin - Site Configuration tab. Once added, you will see a link on the main QC landing page for the Web Cleint.

Site Parmeter:
ALLOW_WEBUI_ACCESS

Value:
Y

More information can be found in the Web Client User's Guide located under Help - Documentation Library.

Please note that the Web Client and GUI client operate independently and customizations/configurations placed in one client will not be reflected in the other client. However, the data itself will be shown in both (i.e. - new defects, tests, etc. will show in both, but required fields or transitions and conditions will need to be duplicated for each client type).