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| obj | source |
|---|---|
| concept | https://developer.mozilla.org/en-US/docs/Learn/Common_questions/Web_mechanics/What_is_a_URL |
URL
The target of an HTTP request is called a "resource", whose nature isn't defined further; it can be a document, a photo, or anything else. Each resource is identified by a Uniform Resource Identifier (URI) used throughout HTTP for identifying resources.
The most common form of URI is the Uniform Resource Locator (URL), which is known as the web address.
Syntax
URL: http://www.example.com:80/path/to/myfile.html?key1=value1&key2=value2#SomewhereInTheDocument
URLs can be absolute like the above or relative like ../parent/path.
Scheme or Protocol
http:// is the protocol. It indicates which protocol the browser must use. Usually it is the HTTP protocol or its secured version, HTTPS. The Web requires one of these two, but browsers also know how to handle other protocols such as mailto: (to open a mail client) or ftp: to handle a file transfer, so don't be surprised if you see such protocols. Common schemes are:
| Scheme | Description |
|---|---|
| data | Data URLs |
| file | Host-specific file names |
| ftp | File Transfer Protocol |
| http/https | Hyper text transfer protocol (Secure) |
| javascript | URL-embedded JavaScript code |
| mailto | Electronic mail address |
| ssh | Secure shell |
| tel | telephone |
| urn | Uniform Resource Names |
| view-source | Source code of the resource |
| ws/wss | WebSocket connections (Secure) |
Domain
www.example.com is the domain name or authority that governs the namespace. It indicates which Web server is being requested. Alternatively, it is possible to directly use an IP address, but because it is less convenient, it is not often used on the Web.
Port
:80 is the port in this instance. It indicates the technical "gate" used to access the resources on the web server. It is usually omitted if the web server uses the standard ports of the HTTP protocol (80 for HTTP and 443 for HTTPS) to grant access to its resources. Otherwise, it is mandatory.
Path
/path/to/myfile.html is the path to the resource on the Web server. In the early days of the Web, a path like this represented a physical file location on the Web server. Nowadays, it is mostly an abstraction handled by Web servers without any physical reality.
Query
?key1=value1&key2=value2 are extra parameters provided to the Web server. Those parameters are a list of key/value pairs separated with the & symbol. The Web server can use those parameters to do extra stuff before returning the resource to the user. Each Web server has its own rules regarding parameters, and the only reliable way to know how a specific Web server is handling parameters is by asking the Web server owner.
Fragment
#SomewhereInTheDocument is an anchor to another part of the resource itself. An anchor represents a sort of "bookmark" inside the resource, giving the browser the directions to show the content located at that "bookmarked" spot. On an HTML document, for example, the browser will scroll to the point where the anchor is defined; on a video or audio document, the browser will try to go to the time the anchor represents. It is worth noting that the part after the #, also known as the fragment identifier, is never sent to the server with the request.