In general, an ID is commonly known as identification. It is a process to identify someone so a system can verify a person is authorized or unauthorized. For example, a valid username and password are needed by many services before the system can be accessed. Like, if you want to log in to your Facebook account, it requires a valid user ID and password to access the Facebook page. If you enter the correct user ID and password, you are identified and can log in to your Facebook account.

User ID (user identification) is a logical entity that is used to log on to an application, online service, or a website. A user ID number is commonly used within any IT-enabled system to identify the users. Additionally, it may be in terms of email address, an account number, or username. Instead of user ID, many websites require an email address to access the web pages, which offers two advantages for users:

• If you want to register yourself on the website, it automatically links your email address with your account.
• It is a simple way to choose a unique username.

In some services, you are required to select a user ID, which is not your email address. For instance, users have to choose a custom username for their profile in such applications like Snapchat and Instagram. Some services require both a username and email address that may allow users to log in using either identifier since they are both unique.

The User ID is an authentication mechanism that is widely used with applications, computing systems, networks, and on the Internet. Despite the user's rights and type of user, every user has a unique identification that differentiates it from other users. Typically, a user ID is used in conjunction with a password in an authentication process. If any user wants to gain access to the system or application, he must provide both of the credentials (user Id and password) correctly. Furthermore, user IDs are used by system administrators to manage overall operations on a particular system, to track user activity, and assign rights.

Username

A username is a number, word, or collection of characters that is also known as a login ID. It uniquely verifies a user on a website, software, or any computing device that requires user authentication. It is used to identify and gain access to a computing system. In the IT and IT-enabled systems that have a multi-user access mechanism, a username is a widely used authentication and authorization technique. Mainly, a username is used with the combination of a password. The function of a username is to identify a user and password works for authentication.

In most services, a username is created between 6 and 14 characters in length by the user. Although a username is an essential part of the information security mechanism, it offers strong security with a password and cannot pose serious threats alone. Because if any hacker or unauthorized person wants to gain access for the information, the authorization depends on the correct input of username and password.

User ID vs Username

The username and user ID are synonymous in many cases. For instance, a website may offer two fields with Username and Password on the user login portal. Another website may provide User ID and Password, which refer to the same objective. Technically, a username is a subset of the user ID. The user ID may be in terms of email address, an account number, or another unique identifier.

ID may also refer to any of the following:

1. ID is a command to show the group ID and numeric user on BSD. For example, the id command prints the effective and real IDs of users and groups on Unix-like operating systems.

Syntax:

1. id [OPTION]... [USERNAME]   

2. ID is a selector in CSS, which is used to specify a style on one HTML element. For example: in the below example, right represents the id that can be used to align the text on the right side on a page. If an id has been used once on an element, it cannot be used with any other element. You can use the class selector if you need to use a style on more than one element.

1. #right {text-align: right;}  

HTML <p> tag with right class

1. <p id="right">This text would be on the right side</p>