Definition
A Uniform Resource Locator (URL) is a string of characters that provides a way to access a resource on the Internet. URLs are used to specify addresses on the World Wide Web. They consist of multiple parts which include the protocol, domain name, and the path to the resource. In everyday language, a URL is also referred to as a web address.
Structure of a URL
A typical URL has the following structure:
protocol://domain_name:port/path?query_string#fragment_id
- Protocol: Indicates the method used to access the resource (e.g., HTTP, HTTPS, FTP).
- Domain Name: The address of the server where the resource is hosted (e.g., www.example.com).
- Port: Optional. The port number through which the connection is made. The default port for HTTP is 80 and for HTTPS is 443.
- Path: Specifies the exact location of the resource on the server (e.g., /folder/page.html).
- Query String: Optional. Contains data to be passed to web applications (e.g., ?id=1234&name=test).
- Fragment Identifier: Optional. Points to a specific part within a web page (e.g., #section2).
Examples of URLs
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Simple URL
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URL with Path
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URL with Query String
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URL with Fragment Identifier
Frequently Asked Questions (FAQs)
What is the difference between a URL and a URI?
While the terms URL and URI are often used interchangeably, a Uniform Resource Identifier (URI) is a more general term that includes both URLs and URNs (Uniform Resource Names). A URL is a type of URI that specifies the location of a resource.
How is HTTPS different from HTTP?
HTTP (HyperText Transfer Protocol) is used for transmitting data over the web. HTTPS (HyperText Transfer Protocol Secure) is HTTP with security, using SSL/TLS to encrypt the data being exchanged to ensure secure communication.
Why are there ports in a URL?
Ports are used to direct the data to the correct service or application on a server. While usually omitted because they use default values, specifying a port can point to non-standard services or multiple services on the same domain.
Can URLs be case-sensitive?
The domain name part of a URL is not case-sensitive, while the path and query string can be case-sensitive, depending largely on the server’s operating system.
What is a query string in a URL?
A query string is the portion of a URL where data parameters are passed to the server or application. It typically starts with a “?” followed by key-value pairs (e.g., ?id=123).
Related Terms
- HTTP (HyperText Transfer Protocol): The foundation of data communication for the World Wide Web.
- HTTPS (HyperText Transfer Protocol Secure): The secure version of HTTP, using encryption.
- URI (Uniform Resource Identifier): A string that identifies a resource either by location (URL) or name (URN).
- Domain Name: The address of a website on the Internet to make it easy to access instead of using the IP address.
- IP Address: The unique string of numbers separated by periods that identifies each computer using the Internet Protocol to communicate over a network.
Online Resources
- ICANN - Internet Corporation for Assigned Names and Numbers
- W3C - World Wide Web Consortium
- IETF - Internet Engineering Task Force
- RFC 3986 - Uniform Resource Identifier (URI): Generic Syntax
Suggested Books for Further Studies
- “Learning Web Design: A Beginner’s Guide to HTML, CSS, JavaScript, and Web Graphics” by Jennifer Niederst Robbins.
- “Understanding the Network: A Practical Guide to Internetworking” by Barry Raveendran Greene.
- “HTTP: The Definitive Guide” by David Gourley and Brian Totty.
- “Web Protocols and Practice: HTTP/1.1, Networking Protocols, Caching, and Traffic Measurement” by Balachander Krishnamurthy and Jennifer Rexford.
Fundamentals of Uniform Resource Locator: Internet Basics Quiz
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