WHM, short for WebHost Manager, is a web-based tool which is used for server administration. There are at least two tiers of WHM, often referred to as "root WHM", and non-root WHM (or Reseller WHM). Root WHM is used by server administrators and non-root WHM (with less privileges) are used by others, like entity departments, and resellers to manage hosting accounts often referred to as cPanel accounts on aweb server. WHM listens on ports 2086 and 2087. WHM is also used to manage SSL Certificates (both server self generated and CA provided SSL certs), cPanel Users, hosting packages, DNS zones, Themes, and Authentication methods. Additionally, WHM can also be used to manage FTP, Mail(POP, IMAP and SMTP) and SSH services on the server. The default automatic SSL (AutoSSL) provided by cPanel is powered by Sectigo (formerly Comodo CA) late 2018. Sectigo is now a commercial Certificate Authority and a provider of purpose-built and automated PKI management solutions. The company released the Sectigo Embedded Firewall for Automotive in 2019.
As well as being accessible by the root administrator, WHM is also accessible to users with reseller privileges. Reseller users of cPanel have a smaller set of features than the root user, generally limited by the server administrator, to features which they determine will affect their customers' accounts rather than the server as a whole. From root WHM, the server administrator can perform maintenance operations such as upgrade and recompile Apache & PHP, install Perl Modules, and upgrade RPMs installed on the system.