A web server ( Latin servire 'serve'; English server 'servant', 'service') is a server that sends documents to clients such as B. Web browser transmits. A web server is the name given to the computer with web server software or just the web server software itself. Web servers are used locally, in company networks and mainly as a WWW service on the Internet. Documents can therefore be made available locally, in-house and worldwide for the required purpose.
The main task of a web server is to deliver static files, e.g. B. immutable HTML or image files, or dynamically generated data, e.g. B. Pages whose content is always created individually according to the profile of a logged in user.
For a complete website, the HTML page including linked design descriptions ( CSS ) and image files ( JPG , PNG , GIF , SVG ) are usually transferred as individual files. For each required file, the web browser has to send a separate request to the web server, i. H. Sometimes hundreds of requests and server responses are necessary to display a complex website. A web server is able to deliver the contents of a website to many different computers at the same time. How quickly user inquiries can be processed depends not least on the complexity of the web content: For example, dynamic web content requires more resources than static web content.
Standardized transmission protocols ( HTTP , HTTPS ) and network protocols such as IP and TCP , usually via port 80 (HTTP) and port 443 (HTTPS), are used as transmission methods. HTTP is the most commonly used protocol; alternatives such as SPDY are only in the testing phase.
With most websites, the content is only compiled from different sources when it is accessed.
Script languages such as ASP , PHP or JSP interpret an HTML document on the server side when it is called and allow the web server to transfer it to the web browser. The previously separated content and the structure of files and databases are processed into one document with the content management system . Websites and applications such as blogs , online forums , online shops etc. use this technology.
In addition to delivering static or dynamic documents, web servers can also fulfill other functions:
- Access restriction
- If the authentication is not managed by the CMS , web servers can also use HTTP authentication .
- The HTTPS method may be used to encrypt server-client communication .
- Cookie management
- Web servers can also manage HTTP cookies .
- If no document is to be delivered at all, but the call is forwarded to another document , the request is redirected with a rewrite engine .
- Any errors or successes are reported to the browser with HTTP status codes and an error page .
- On a web server, all requests are usually recorded in a log file , from which statistics on the number of accesses per page can be generated using log file analysis. HTTP is a connectionless and stateless protocol. This means that it is generally possible to assign a request to a user via the IP address. However, the assignment is z. B. not always clear with web access via LAN. The indication of visits , hits , users , etc. is therefore only of limited use. Intermediate proxy servers , which act as clients to the web server, make this assignment even more difficult.
- In the case of large access numbers, the complex dynamic content delivery can be buffered and the web server, scripts and databases can be protected with HTTP caching .
If a user is connected to the Internet and enters a web address in the address line of his web browser, e.g. B. "http://de.wikipedia.org/wiki/Webserver", the web browser converts the domain component "de.wikipedia.org" contained therein into an IP address by the operating system by querying a DNS server , e.g. . B. 188.8.131.52 ( IPv4 ) or 2a00: 1450: 8007 :: 63 ( IPv6 ). The web browser then sends the full address (URL) to this IP address on port 80. From there, the web server responds and sends the corresponding results page of the homepage to the web browser.
In 1989, Tim Berners-Lee proposed a project to his employer, CERN , the European Organization for Nuclear Research, to ensure the exchange of information among the several thousand employees. Among other things, he stated that a “web” of interconnected information was more useful than a fixed hierarchy and that the storage software must be separate from the display software. He was able to realize this project and in the course of it developed the first web server CERN httpd and the first web browser WorldWideWeb , both under NeXTStep . The CERN httpd was ported to Unix and VMS and further developed until 1996.
In 1994 Tim Berners-Lee decided to found the World Wide Web Consortium in order to regulate the further development of the technologies used (protocols, display languages, Unicode, etc.).
The most popular web server computer programs are Apache HTTP Server , nginx , Microsoft Internet Information Services, and Google Web Server . Apache and nginx are free software , while Microsoft IIS and Google Web Server are proprietary software .
Other web server software:
- AOLserver ( America Online ; free software)
- Apache Tomcat (Apache Software Foundation; free software)
- Boa (web server) (GNU General Public License)
- CERN httpd (open source)
- Hiawatha (GNU General Public License)
- Hunchentoot (web server in Common Lisp , BSD-like license)
- iPlanet (Sun Microsystems)
- Jetty (for web applications in Java )
- W3C Jigsaw (Open Source)
- lighttpd (BSD license)
- Node.js (Node.js Foundation; MIT license)
- uHTTPd ( Freifunk / OpenWrt ; free software)
- Zope (Zope Corporation, free software)
Estimates of market shares are based on different measurement methods and therefore differ massively in some cases:
- Netcraft "all sites" measures the type of web server in a domain regardless of how often it is visited. The website of a private person counts as much as that of Google or Facebook (this parameter is further collected for historical reasons)
- Netcraft "active sites" excludes pages that do not change over a long period of time, i.e. mostly private homepages with static content or domains with exclusively automatically generated content
- Netcraft "top million" is a third category from the same company that only considers the most visited domains
- W3Tech also takes into account the most frequently visited domains
|date||source||Apache||Microsoft IIS||nginx||Google Web Server|
|January 2013||Netcraft , "all sites"||55.26%||16.93%||12.64%||3.58%|
|July 2013||Netcraft , "all sites"||52.19%||19.65%||13.60%||3.92%|
|January 2014||Netcraft , "all sites"||41.64%||29.42%||14.40%||2.47%|
|July 2014||Netcraft , "all sites"||51.14%||14.35%||11.86%||8.12%|
|January 2015||Netcraft , "all sites"||39.74%||27.52%||14.61%||2.30%|
|July 2015||Netcraft , "all sites"||38.34%||26.52%||15.47%||2.38%|
|January 2016||Netcraft , "all sites"||33.56%||28.95%||15.60%||2.29%|
|July 2016||Netcraft , "all sites"||31.72%||35.26%||15.92%||2.10%|
|January 2017||Netcraft , "all sites"||21.51%||45.66%||17.63%||1.00%|
|February 2017||Netcraft , "all sites"||20.89%||43.16%||19.42%||1.03%|
|Netcraft , "active sites"||45.78%||9.22%||19.60%||6.70%|
|December 2018||Netcraft, "all sites"||18.94%||41.53%||21.63%||1.44%|
|Netcraft, "active sites"||30.05%||6.72%||22.11%||7.81%|
|Netcraft, "top million"||33.04%||9.33%||25.89%||k. A.|
|W3Techs, "top 10 million"||44.4%||8.9%||41.0%||0.9%|
|December 2019||Netcraft, "all sites"||24.36%||14.59%||37.77%||2.94%|
|Netcraft, "active sites"||29.25%||4.96%||19.14%||9.59%|
|Netcraft, "top million"||30.42%||8.17%||25.46%||1.82%|
|W3Techs, "top 10 million"||41.8%||7.9%||31.3%||1.1%|
- Comparison of web servers in the English language Wikipedia
- With 165 words into the future . ( Stern article on the 20th anniversary of the WWW)
- Servicing the first web server - Tim Berners-Lee's NeXT (pictures of the first web server, operated by Tim Berners-Lee )
- What is a web server? . 1und1.de/digitalguide. Retrieved December 4, 2017.
- CERN httpd . World Wide Web Consortium. Retrieved April 25, 2009.
- Web Server Survey | Netcraft
- How many active sites are there? Netcraft.com, accessed on January 29, 2019 (English, In the early days of the web, hostnames were a good indication of actively managed content providing information and services to the Internet community. The situation is now considerably more blurred [..] ).
- Active Sites. Retrieved on January 29, 2019 (It is therefore desirable to find a way to count sites, rather than IPs, but excluding those sites which come from a standard or computer-filled template.).
- Technologies Overview. W3Techs, accessed January 29, 2019 (We include only the top 10 million websites [..] in the statistics in order to limit the impact of domain spammers.).
- Netcraft February 2017 Web Server Survey
- Usage of web servers for websites. W3Techs, accessed on January 29, 2019 .