Addon Domain

An additional domain name associated with a cPanel account. Each addon domain is stored in its own directory that can be configured during its creation. This allows clients to manage multiple domains from a single cPanel account. Addon domains must be registered with a domain registrar and configured to point to our servers to properly function.

Anonymous FTP

A process whereby visitors without FTP accounts may upload and download files to and from a website. Because it poses security risks, we do not offer anonymous FTP.


A program that receives requests from web browsers and responds by "serving" web pages to the browser. For this reason, it's called a web server.

Apache Handler

A means of telling the Apache software how to process a given type of file. By default, Apache only handles certain file types. You can configure Apache handlers for other file types using an .htaccess file. For more information, see Apache's handler documentation.

Auto Responder

Auto responders allow you to automate replies to incoming email. In cPanel, this feature can be useful for confirming the receipt of mail, or for informing correspondents that the recipient is unavailable (for example, while on vacation).


Bounce messages erroneously sent to a domain whose name has been forged as the sender of spam. Using SPF on your mail server should reduce backscatter.


A copy of your website's files, directories, and databases. Keeping a current backup of your website either remotely or on your personal computer is highly recommended.


The amount of data transferred to and from a server. Every time a visitor views a file (whether it's a web page, image, video, or audio file), that file is transferred to the visitor's computer. Bandwidth is the total size of all these files transferred to visitors' computers. Using too much bandwidth can affect the performance of the server.

Bandwidth Limit

A limit imposed on the amount of data an account is allowed to transfer per month.


An option for handling mail received by the default or catch-all email address of a cPanel account. The "blackhole" option discards mail after it is accepted. For this reason, it can result in more spam being sent to your users, and it places a larger load on the server than the "fail" option.

Bounce Message

An email reply informing a sender that there was a problem delivering an email.

Brute Force Attack

A type of attack wherein the attacker enters a large number of combinations of characters, in an attempt to decrypt a key. Similar to a Dictionary Attack.

Catch-All Address

The email address to which cPanel routes any email message sent to email accounts that do not exist on a domain. Also known as a Default Address.


An electronic document that states the identity of a server so that the end user knows that he or she is communicating with the correct website.

Certificate Authority

An entity that issues digital certificates for server verification.

Certificate Authority (CA) Bundle

A file on the server that verifies that your public and private keys were issued by a trusted entity. If your SSL provider sent you a CA bundle file, you can install it using the "Install SSL Certificate" feature in cPanel. Also known as an Intermediate Certificate.

CGI (Common Gateway Interface)

A protocol that lets a web server communicate with scripts and other software.


An SSH command that allows you to set permissions (read, write, or execute) on a file or directory.

CIDR (Classless Inter-Domain Routing)

A routing method that assigns each Internet user to a four-part IP address, with each part separated by a decimal, followed by a slash, and a number between 0 and 32.

CLI (Command Line Interface)

A means of communicating with a server by typing commands. This is also often called a shell.

CPAN (Comprehensive Perl Archive Network)

The main repository of Perl modules, pieces of Perl software. The CPAN library contains over 120,000 modules, most of which are free of charge. You can search CPAN and install Perl modules from cPanel.


A web-based control panel designed to simplify website maintenance for website owners.

CPU Load

The amount of processing ability currently being consumed by programs on the server, measured in a percentage. More information about CPU loads can be found here.

Cron Job

A command on a server, executed at regular intervals. These commands are stored in a configuration file called crontab. You can manage your cron jobs using the "Cron Manager" feature in cPanel.

CRT (Certificate) File

An SSL certificate, an electronic document which ties a public key to a trusted entity. This electronic document is a key piece in an authentication process.

CSR (Certificate Signing Request)

A request, which you send to a Certificate Authority, for an SSL certificate. You can generate a CSR using the "Generate CSR" feature in cPanel, but since authorities vary with regard to the information they require, you should check their requirements before applying for a certificate.

CSS (Cascading Style Sheets)

A style sheet programming language that describes how a document, often written for the web in HTML, should appear.


A computer program that runs as a background process, rather than being visible to, and directly controlled by, the user.

Data Center

A facility used to house servers. A data center is a safe place to keep a server as it includes backup power supplies, multiple communication connections, and environmental controls.

Dedicated IP Address

A dedicated IP address is different from a shared IP address in that only one cPanel account is assigned to it. A dedicated IP address is needed to install an SSL certificate. There is no SEO benefit or performance difference between a shared and dedicated IP address.

Default Address

The email address to which cPanel routes any email message sent to email accounts which do not exist at a domain. Also known as a Catch-All Address.


A feature that is no longer supported.

DHA (Directory Harvest Attack)

A technique employed by spammers whereby they attempt to find valid email addresses through guesswork, using various permutations of common addresses.

Dictionary Attack

A method whereby a malicious user tries to guess a password using words found in a dictionary. Similar to a Brute Force Attack.

Directory (Folder)

A repository for files, analogous to a file folder on a personal computer. In website management, a directory will contain the website's files.

Disk Space Quota

A limit placed on the amount of disk space an account is allowed to use.

DKIM (Domain Keys Identified Mail)

The replacement for the older DomainKeys protocol. Like DomainKeys, DKIM attempts to verify the origins of email messages.

DNS (Domain Name System)

The component of the Internet that acts as a "phone book," converting human-readable domain names (such as into computer-readable IP addresses (such as

DNS Zone

An administrative space or portion of the Domain Name System. This space is responsible for directing web traffic to the correct location. An example is, a DNS zone whose servers direct its web traffic.

DNS Zone File

A file on the server that primarily maps IP addresses to domain names. A correctly configured zone file must exist in order for visitors to access your website from the Internet.


The name a site owner gives a website, which will appear in the website's URL and email addresses. Usually seen as, where example is meant for the domain name.

Domain Forwarding

A technique that allows you or your users to automatically send visitors to a domain when they access another domain. For example, a user may reach by typing See Redirect.


A deprecated email authentication method that attempts to verify that a message actually came from the domain it appears to have come from. See DKIM (Domain Keys Identified Mail).


An option for handling mail received by the default or catch-all email address for a cPanel account. The fail option returns all mail received by the default address as undeliverable.


A tool that lets you forward a copy of every email message you receive to another address. When a forwarder is set up, you will still receive mail at the original recipient address. If, however, you create a forwarder without first creating the original address, messages will be forwarded to the end address without being sent to the original address, as it does not exist.

FQDN (Fully Qualified Domain Name)

A name that uniquely defines a domain's location. It is usually seen as with a trailing dot. For the purposes of cPanel, including a final dot is not necessary, but the domain name must contain at least two dots. FQDNs must be written in lowercase letters.

FTP (File Transfer Protocol)

A method of transferring files from one computer to another. cPanel comes equipped with an FTP server that can be configured to the website owner's preference. An FTP client must be installed on the local computer in order to send files to and receive files from the FTP server. It is highly recommended that clients disable FTP, which can be done using the "Disable FTP Access" feature in cPanel, and use a secure protocol, such as SCP or SFTP.

GD (Graphics Draw)

A library for dynamically manipulating images. It can create GIF, JPEG, PNG, and other images. GD is similar to ImageMagick, another image manipulation library.


A program which compresses files for disk space conservation, minimizing transfer times, and making the transfer of multiple files easier. The compressed files use the filename extension .gz. The gzip is often used with tar to create a "tarball" file (which ends with .tar.gz).

Home Directory

A cPanel account's highest-level directory that contains all the files and directories used by websites managed by the account. Files placed in a home directory are not viewable online unless they reside in the public_html directory. The exception to this is if you create an Addon or Sub Domain and set the Document Root outside the public_html directory.


The unique, human recognizable name by which a server will be known across the Internet. For example, Please note that a server's hostname is distinct from your domain name.


A file that resides in a specific directory, and contains configuration information applying to that directory. The .htaccess file may also contain authentication instructions.

HTML (Hypertext Markup Language)

The language in which most pages on the World Wide Web (WWW) are written.


A file that resides in a specific directory, along with an .htaccess file. The .htpasswd file contains encrypted password information when authentication has been set up for the directory.

HTTP (Hypertext Transfer Protocol)

The method (protocol) for transferring data over the Internet.


The configuration file for the Apache web server. More information about httpd.conf can be found here.


An image manipulation library that can be used by PHP to manipulate and create images. ImageMagick is similar to GD, another image manipulation library.

IMAP (Internet Message Access Protocol)

Along with POP3, one of the two most widely used email transfer methods. IMAP synchronizes email account information with the mail server on a regular basis. If a user logs into multiple computers to check email, IMAP will allow the user to see what messages they have viewed, replied to, forwarded, etc. POP3 does not display this information.

Index Page

The page, most often titled index.php or index.html, viewed by default when a visitor accesses a directory of a website. If no index page exists for the specified directory, the visitor will see a list of files in that directory, unless indexing is disabled.

Internet Media Type

Previously called a MIME (Multipurpose Internet Mail Extensions) Type, this component of a file identifies the file type, so that web browsers know how to handle it.


ionCube is a loader that protects the intellectual property of software developers who produce software written in PHP. The Zend Guard Loader is another tool that can encode and decode PHP scripts. Both of these loaders are installed by default.

IP (Internet Protocol) Address

A number that identifies a computer on a network, making it possible for other computers to find and communicate with it.

Jailed Shell

A CLI configuration that restricts users' access rights by partitioning the server into smaller parts. This will prevent a user from leaving his or her user directory, restricting access to the file system and some commands. Also known as Jailshell.


JavaScript is a scripting language based on the concept of prototype-based programming. The language is best known for its use in websites as client-side JavaScript. It is distantly related to Java, with their main similarity being the C programming syntax.


A central component of the server's operating system. The kernel manages communications between the user and the server's resources, such as its processor and the memory.


A file, automatically created by the server, that records activities performed by specific programs and applications on the server. For instance, error logs are lists of errors generated by Apache that visitors have encountered on a website.

Message Transfer Agent

A program responsible for sending and receiving email messages. Also known as a Mail Transfer Agent (MTA) or Mail Relay.


In encryption algorithms such as RSA, the modulus is the number that both the private and public keys have in common. You can view a key's modulus using the "SSL Key Manager" feature in cPanel.

MX (Mail eXchanger) Entry

A record that specifies where email should be sent for a domain, as it contains the mail server's IP address. When using a third-party email service or custom mail delivery, you may need to change the MX record for a domain using the "MX Records" feature in cPanel.


A relational database management tool and server, as well as the type of database it manages. Databases are an integral part of web applications, such as shopping carts, bulletin boards, and blogs. cPanel provides an integrated MySQL interface as well as a MySQL database editing tool called phpMyAdmin.


A piece of software that obtains DNS information from a physical nameserver, a computer that contains a list of domain names and their corresponding IP addresses. These computers are spread through the Internet and allow visitors to access a domain via its IP address.

Nameserver software gathers data about domains over time, therefore, changes to DNS records can take up to a week to reach (or propagate) all the nameservers on the Internet. Our nameservers are:


This is a Linux system account with the UID of 99. This system account is used to execute CGI and PHP scripts if suEXEC is disabled..

Parked Domain

A second domain that points to a primary domain. When users attempt to access the parked domain, they will see the main website. For example, both and go to the same place, as is a parked domain for Parked domains must be registered with a domain registrar and configured to point to our servers to properly function.

PASV (Passive Mode)

A mode for FTP connections that will initiate connections from the client side. Using this mode may be helpful if a user is having problems connecting to an FTP server through a firewall.

PEAR (PHP Extension and Application Repository)

A repository of PHP code. You can use the "PHP Extension Manager" feature in cPanel to search for and install PEAR packages consisting of PHP programs which can perform useful functions for your website.


Known for its ability to process text, Perl is a useful language for web applications. Perl applications are commonly found as .pl, .pm, and .cgi files and may require Perl modules. More information about Perl can be found here.

Perl Module

A piece of software written in the Perl language. Modules are common pieces of software that are reused often. For example, rather than writing a set of functions to display calendars, a user can simply use a calendar module.


A computer scripting language in which many web-based applications are written. PHP applications are commonly found with the filename extension .php. Some PHP applications require PEAR packages, which can be installed through the "PHP Extension Manager" feature in cPanel. The following versions of PHP are available on our servers:

More information about PHP can be found here.

PHP Package

A piece of software written in the PHP language.


A graphical application that allows website administrators to manipulate and manage MySQL databases over the Internet. Full documentation for phpMyAdmin can be found here.

PID (Process ID)

A unique number that your server assigns to each process that runs.

POP3 (Post Office Protocol Version 3)

Along with IMAP, one of the two most widely used email transfer methods. POP3 simply copies every message in an email account to a local computer, removing it from the mail server. No information is sent back to the email account about message replies, forwarding, etc. If an account owner uses multiple computers to check email, it is advisable to use IMAP instead of POP3.

POSIX (Portable Operating System Interface)

A standardized collection of commands for the Linux operating system.


An instance of a program running on the server.


The spread of a website's DNS information across the Internet.


Short for a proxy server. This server receives requests from users and forwards those requests to other servers.


A subdirectory, located inside the Home Directory, that contains files that are publicly accessible via HTTP. The www directory is a symbolic link (or shortcut) to public_html. Any files and folders inside of public_html are visible over the Internet, unless the website owner specifically protects them with password protection or using the .htaccess file or "Password Protection" feature in cPanel.


A programming language which is used for many applications. More information about Python can be found here.


A feature that sends users to a different domain than the one they were trying to access. For example, a user may reach by typing You can setup temporary or permanent redirects using the "Redirect Manager" feature in cPanel. See Domain Forwarding.


A web page that links to a site. Also called an "HTTP referer." This spelling is the industry standard term, though it is based on a misspelling of "referrer."

Regular Expressions

Often seen as regex or regexp, regular expressions are a means of formatting text so that a specified program can process it, using it to search in a prescribed way. A wildcard character, such as an asterisk, is an example of a regular expression.


The system account. This account is used by a system administrator and carries full privileges for configuring a computer system. Also called "superuser."

Root Directory

The highest level directory on a server, usually notated by a forward slash.


A webmail client that allows users to check email through an Internet browser rather than an email client.


An algorithm for generating public and private keys when sending encrypted data between a local machine and a remote machine. The name of this method is not an abbreviation; it is named after its three inventors.

SCP (Secure Copy Protocol)

A method of transferring encrypted files from one computer to another. This method prevents data from being intercepted and read. This secure protocol is preferred over FTP.


Software that allows a user to interact with a server. Many shells allow the user to type commands, and are often referred to as CLIs, or command line interfaces.

SMTP (Simple Mail Transfer Protocol)

This protocol is the standard for transmitting email messages across the Internet. It is namely used for sending mail to a mail server's relayer.


Unsolicited email sent in bulk, usually by an automated system or exploited web application.

SPF (Sender Policy Framework)

A feature that allows a recipient server to verify that an email message has really been sent from the domain specified in the From: field. Enabling SPF can prevent your server from receiving replies to spam that has forged your domain name as part of the sender's address. SPF only works if both the sending and receiving mail servers have SPF enabled.


An attack wherein the attacker conceals his identity by appearing as another user through the falsification of data, such as email headers. Enabling SPF makes it more difficult for spammers to spoof a domain.

SQL Database

A type of relational database management system

SSH (Secure Shell)

A network protocol that allows a user to log into a remote machine securely. You can create keys for authenticating a user's identity during SSH login through the "Manage SSH Keys" feature in cPanel.

SSL (Secure Sockets Layer)

A cryptographic scheme that allows for secure interaction between a web browser and a web server. All sensitive data (credit card numbers, login information, etc.) that is transmitted over the Internet should be protected by SSL. Website owners can install an SSL certificate on a website (via the "Install SSL Certificate" feature in cPanel) to allow the site to be protected by SSL.

SSL Certificate

An electronic document (using the filename extension .crt) which binds a public key to an identity consisting of an email address, company, and location. This electronic document is a key piece in an authentication process.

Sub Domain

A subsection of a website that exists as a subdirectory in the website owner's home folder. If the domain were, then the sub domain URL would appear as


A feature provided by Apache that allows users to run CGI and SSI applications on the system as themselves. By default, CGI and SSI are executed using the system account known as nobody with the UID of 99.


Originally derived from "Tape Archive," a program that collates files for transfer or distribution. Files processed by this program are usually compressed, commonly called "tarballs," and use the filename extension .tar. Due to the compression commonly used, .tar often precedes the .gz file extension.


A file collated by the tar program, and usually compressed.


A network protocol that allows a user to log into a remote machine user account remotely. Telnet is similar to SSH, but less secure. Telnet should not be used to connect to your web site except for testing purposes. Login information is sent through Telnet as plain text and can be easily intercepted.

TTL (Time To Live)

Specifies how long a particular record should be kept in memory before it should be deleted. This is most often used within DNS.

UID (User ID)

The unique user number that any user on your server will be assigned during a session.

Unix Time

Unix time is measured by the number of seconds that have passed since the 1st of January, 1970 UTC.

URI (Universal Resource Identifier)

On the web, a URI is a string of characters that identifies a website. URI is often used synonymously with the terms "URL" and "web address," although there are technical differences among the three.

URL (Universal Resource Locator)

On the web, a URL is a string of characters that identifies the location of a website. Since IP addresses are difficult to remember, URLs are used instead. For example, it is much easier to remember to go to than URL is often used synonymously with the terms "URI" and "web address," although there are technical differences among the three.


A person who uses a computer to accomplish some purpose.


A person who views your website.

Web Browser

An application used to view and interact with sites and pages on the World Wide Web, such as Chrome, Firefox, Internet Explorer, and Opera.

Web Root

The top-most directory of your website (namely, public_html or www), inside which all of the files and subdirectories for your website reside. Also known as the document root.

Web Server

A program, such as Apache or LiteSpeed, which receives requests from clients (web browsers), retrieves the requested web pages, and "serves" them to the clients.


Any application which allows website owners to access email through a web browser. The main advantage to webmail is the ability to access the email account from any computer connected to the Internet without having to install or configure a specific mail program.

WHM (WebHost Manager)

Companion software to cPanel, designed for web hosting companies and system administrators.


A command that can be executed in a terminal session in order to find out who owns a domain. For example, whois will return the ownership information for Crucial Web Hosting.


A DNS Zone, an administrative space or portion of the Domain Name System. This space is responsible for directing web traffic to the correct location. An example is, a DNS zone whose servers direct its web traffic.

Zone File

A file on the server that primarily maps IP addresses to domain names. A correctly configured zone file must exist in order for visitors to access the server from the Internet.