HTML Uniform Resource Locators
A URL is another word for a web address.
A URL can be composed of words, such as "http://google.com", or an Internet Protocol (IP) address: 74.125.232.138 Most people enter the name of the website when surfing, because names are easier to remember than numbers.
URL - Uniform Resource Locator
Web browsers request pages from web servers by using a URL.
When you click on a link in an HTML page, an underlying <a> tag points to an address on the world wide web.
A Uniform Resource Locator (URL) is used to address a document (or other data) on the world wide web.
A web address, like this: http://www.google.com/html/default.asp follows these syntax rules:
scheme://host.domain:port/path/filename
Explanation:
- scheme - defines the type of Internet service. The most common type is http
- host - defines the domain host (the default host for http is www)
- domain - defines the Internet domain name, like w3schools.com
- port - defines the port number at the host (the default port number for http is 80)
- path - defines a path at the server (If omitted, the document must be stored at the root directory of the web site)
- filename - defines the name of a document/resource
Common URL Schemes
The table below lists some common schemes:
| Scheme | Short for.... | Which pages will the scheme be used for... |
|---|---|---|
| http | HyperText Transfer Protocol | Common web pages starts with http://. Not encrypted |
| https | Secure HyperText Transfer Protocol | Secure web pages. All information exchanged are encrypted |
| ftp | File Transfer Protocol | For downloading or uploading files to a website. Useful for domain maintenance |
| file | A file on your computer |
URL Encoding
URLs can only be sent over the Internet using the ASCII character-set.
Since URLs often contain characters outside the ASCII set, the URL has to be converted into a valid ASCII format.
URL encoding converts characters into a format that can be transmitted over the Internet.
URL encoding replaces non ASCII characters with a "%" followed by two hexadecimal digits.
URLs cannot contain spaces. URL encoding normally replaces a space with a + sign.
URL Encoding Examples
| Character | URL-encoding |
|---|---|
| € | %80 |
| £ | %A3 |
| © | %A9 |
| ® | %AE |
| À | %C0 |
| Á | %C1 |
| Â | %C2 |
| Ã | %C3 |
| Ä | %C4 |
| Å | %C5 |
