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The term URL is an acronym for the designation "Uniform Resource Locator".

This describes an address that provides a path to a certain file on a server. This source can be accessed via a network protocol such as http, https or ftp. Per the definition, the purpose of a URL is to allow a resource to be precisely identified and called up with the help of a special network protocol. Nowadays, in everyday use, it is mostly the internet address or web address that is spoken of when what is meant is the URL. Generally, URLs are related to websites. URLs are called up with the help of web browsers.

Creation of the URL

Every website can be retrieved via an IP address. In practice it would be very inconvenient if a user had to enter an extended numeric string every time they wanted to visit an internet site. As the internet developed in the 1990s, the researcher Tim Berners-Lee sought out a standard that would make it possible to access documents via the internet.

Finally, in 1994, the RFC 1738 standard was developed and published. It initially refers to the “Universal Resource Identifier”. In the same year a subtype was created with the “Uniform Resource Locator”. And so the internet address as most users recognize it today was born.

The structure of a URL

In its simplest form, a URL is made up of three parts: Protocol (https://, ftp://), domain or server name ( and file path (/directory/file.html). The file path can be made up of numerous directory levels.

If a file is not called up via a browser or other client on the web, but by another server, a URL can also look like this:

https://peter:[email protected]:8080/index.html

In this case the URL, alongside the protocol/schema, is still made up of the user name with password, the host of the file ( as well as the port (8080) via which the data can be called up.

Relative URLs can also be used within an HTML document. This means that the protocol and server name are omitted. Only the directory and file name are given in the code, for example /directory/file.html. If a relative URL is used on a website, a browser always reverts back to the address of the domain server on which it is currently located when such a link is clicked.

Coding of URLs

To ensure there are no errors in the call up and interpretation of URLs, they can only contain certain characters as part of URL encoding. The so-called ASCII character set is used for this. This makes it possible to use ampersands (&) or hyphens in URLs without the browser misinterpreting them. If, for example, there is an uncoded space in a URL, the browser aborts further encoding. Only with the help of conversion of ASCII characters in a percentage can browsers correctly read out the URLs. This applies to umlauts or ß, for example.

Problems of this type regularly occur if article headlines are automatically used by CMS for the URL. In the source code, coded URLs can be marked with the help of the MIME type.

The coding of URLs also ensures that certain characters are reserved for functions within the URL. Reserved characters are:

  • Question mark (?): It initiates the so-called “query string” of a URL. This is a character string with certain parameters that are used for tracking, for example.
  • Equals sign (=): These characters are set between the parameters and the value.
  • Ampersand (&): This is a separator between the individual parameters in a query string.
  • Hash (#): This character refers to an anchor link within a document.

The non-reserved characters include the numbers 0 to 9 as well as letters A to Z in lower and upper case. These characters also have no function: - _ ~. Depending on the desire of the programmer, they can each have a different meaning.

Domain vs. URL

Nowadays the terms domain and URL are often used synonymously. However, in practice, there is a significant difference. While the URL is made up of the domain name and the path entry in the WWW, the domain is only the name of the area in the so-called Domain Name System (DNS). The name of the domain can be chosen relatively freely and is assigned to a top-level domain.

For example: The URL of our site is “”. Our domain, on the other hand, is “”

URL relevance in SEO

For a long time, keywords in the URL were important for search engine optimization . This allowed webmasters to attain better rankings with keyword domains on search engines such as Google. Generally it was assumed that corresponding keywords in the URL better reflect the topic and therefore benefits could be created in the ranking . In fact, keywords in the URL can help users and search engines to thematically orientate themselves towards a website.

Orientation can, for example, be made easier with short URLs. In principle, Google is also able to read out URLs with more than 1,000 characters without any problems.

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