Search engine optimization (SEO) is the process of improving the mood and total of website traffic to a website or a web page from search engines. SEO targets unpaid traffic (known as “natural” or “organic” results) rather than take in hand traffic or paid traffic. Unpaid traffic may originate from different kinds of searches, including image search, video search, academic search, news search, and industry-specific vertical search engines.

As an Internet promotion strategy, SEO considers how search engines work, the computer-programmed algorithms that dictate search engine behavior, what people search for, the actual search terms or keywords typed into search engines, and which search engines are preferred by their targeted audience. SEO is performed because a website will receive more visitors from a search engine as soon as websites rank higher on the search engine results page (SERP). These visitors can next potentially be converted into customers.

Webmasters and content providers began optimizing websites for search engines in the mid-1990s, as the first search engines were cataloging the in advance Web. Initially, all webmasters forlorn needed to consent the residence of a page, or URL, to the various engines, which would send a web crawler to crawl that page, extract friends to additional pages from it, and recompense information found upon the page to be indexed. The process involves a search engine spider downloading a page and storing it upon the search engine’s own server. A second program, known as an indexer, extracts information about the page, such as the words it contains, where they are located, and any weight for specific words, as skillfully as everything links the page contains. All of this suggestion is after that placed into a scheduler for crawling at a sophisticated date.

Website owners endorsed the value of a high ranking and visibility in search engine results, creating an opportunity for both white cap and black hat SEO practitioners. According to industry analyst Danny Sullivan, the phrase “search engine optimization” probably came into use in 1997. Sullivan credits Bruce Clay as one of the first people to popularize the term.

Early versions of search algorithms relied on webmaster-provided guidance such as the keyword meta tag or index files in engines like ALIWEB. Meta tags have enough money a guide to each page’s content. Using metadata to index pages was found to be less than reliable, however, because the webmaster’s another of keywords in the meta tag could potentially be an inaccurate representation of the site’s actual content. Flawed data in meta tags, such as those that were not accurate, complete, or falsely attributes, created the potential for pages to be mischaracterized in irrelevant searches.^{[dubious – discuss]} Web content providers afterward manipulated some attributes within the HTML source of a page in an try to rank capably in search engines. By 1997, search engine designers recognized that webmasters were making efforts to rank with ease in their search engine and that some webmasters were even manipulating their rankings in search results by stuffing pages when excessive or irrelevant keywords. Early search engines, such as Altavista and Infoseek, adjusted their algorithms to prevent webmasters from manipulating rankings.

By heavily relying upon factors such as keyword density, which were exclusively within a webmaster’s control, early search engines suffered from abuse and ranking manipulation. To meet the expense of better results to their users, search engines had to get used to to ensure their results pages showed the most relevant search results, rather than unrelated pages stuffed afterward numerous keywords by unscrupulous webmasters. This meant distressing away from stifling reliance upon term density to a more holistic process for scoring semantic signals. Since the feat and popularity of a search engine are positive by its achievement to produce the most relevant results to any perfect search, poor setting or irrelevant search results could help users to find other search sources. Search engines responded by developing more obscure ranking algorithms, taking into account additional factors that were more hard for webmasters to manipulate.

Companies that hire overly uncompromising techniques can get their client websites banned from the search results. In 2005, the Wall Street Journal reported on a company, Traffic Power, which allegedly used high-risk techniques and bungled to welcome those risks to its clients. Wired magazine reported that the thesame company sued blogger and SEO Aaron Wall for writing roughly the ban. Google’s Matt Cutts future confirmed that Google did in reality ban Traffic Power and some of its clients.

Some search engines have afterward reached out to the SEO industry and are frequent sponsors and guests at SEO conferences, webchats, and seminars. Major search engines provide guidance and guidelines to urge on with website optimization. Google has a Sitemaps program to back webmasters learn if Google is having any problems indexing their website and as well as provides data upon Google traffic to the website. Bing Webmaster Tools provides a quirk for webmasters to give in a sitemap and web feeds, allows users to determine the “crawl rate,” and track the web pages index status.

In 2015, it was reported that Google was developing and promoting mobile search as a key feature within far along products. In response, many brands began to take a different way in to their Internet promotion strategies.

In 1998, two graduate students at Stanford University, Larry Page and Sergey Brin, developed “Backrub,” a search engine that relied upon a mathematical algorithm to rate the stress of web pages. The number calculated by the algorithm, PageRank, is a comport yourself of the total and strength of inbound links. PageRank estimates the likelihood that a total page will be reached by a web user who randomly surfs the web and follows connections from one page to another. In effect, this means that some friends are stronger than others, as a progressive PageRank page is more likely to be reached by the random web surfer.

Page and Brin founded Google in 1998. Google attracted a faithful following in the midst of the growing number of Internet users, who liked its simple design. Off-page factors (such as PageRank and hyperlink analysis) were considered as with ease as on-page factors (such as keyword frequency, meta tags, headings, links and site structure) to enable Google to avoid the nice of exploit seen in search engines that unaccompanied considered on-page factors for their rankings. Although PageRank was more hard to game, webmasters had already developed link-building tools and schemes to imitate the Inktomi search engine, and these methods proved similarly applicable to gaming PageRank. Many sites focus upon exchanging, buying, and selling links, often on a omnipresent scale. Some of these schemes, or partner farms, involved the commencement of thousands of sites for the sole aspire of colleague spamming.

By 2004, search engines had incorporated a wide range of undisclosed factors in their ranking algorithms to condense the impact of associate manipulation. In June 2007, The New York Times’ Saul Hansell stated Google ranks sites using higher than 200 substitute signals. The leading search engines, Google, Bing, and Yahoo, do not permit the algorithms they use to rank pages. Some SEO practitioners have studied different approaches to search engine optimization and have shared their personal opinions. Patents united to search engines can provide guidance to better understand search engines. In 2005, Google began personalizing search results for each user. Depending on their history of previous searches, Google crafted results for logged in users.

In 2007, Google announced a campaign against paid links that transfer PageRank. On June 15, 2009, Google disclosed that they had taken measures to mitigate the effects of PageRank sculpting by use of the nofollow attribute on links. Matt Cutts, a well-known software engineer at Google, announced that Google Bot would no longer treat any no follow links, in the similar way, to prevent SEO support providers from using nofollow for PageRank sculpting. As a repercussion of this change, the usage of nofollow led to evaporation of PageRank. In order to avoid the above, SEO engineers developed interchange techniques that replace nofollowed tags similar to obfuscated JavaScript and thus permit PageRank sculpting. Additionally, several solutions have been suggested that affix the usage of iframes, Flash, and JavaScript.

In December 2009, Google announced it would be using the web search records of all its users in order to populate search results. On June 8, 2010 a extra web indexing system called Google Caffeine was announced. Designed to permit users to find news results, forum posts, and other content much sooner after publishing than before, Google Caffeine was a alter to the quirk Google updated its index in order to make things operate up quicker upon Google than before. According to Carrie Grimes, the software engineer who announced Caffeine for Google, “Caffeine provides 50 percent fresher results for web searches than our last index…” Google Instant, real-time-search, was introduced in late 2010 in an try to make search results more timely and relevant. Historically site administrators have spent months or even years optimizing a website to growth search rankings. With the growth in popularity of social media sites and blogs, the leading engines made changes to their algorithms to allow fresh content to rank quickly within the search results.

In February 2011, Google announced the Panda update, which penalizes websites containing content duplicated from new websites and sources. Historically websites have copied content from one other and benefited in search engine rankings by fascinating in this practice. However, Google implemented a other system that punishes sites whose content is not unique. The 2012 Google Penguin attempted to penalize websites that used manipulative techniques to attach their rankings upon the search engine. Although Google Penguin has been presented as an algorithm aimed at lawsuit web spam, it really focuses on spammy friends by gauging the mood of the sites the contacts are coming from. The 2013 Google Hummingbird update featured an algorithm tweak designed to increase Google’s natural language management and semantic deal of web pages. Hummingbird’s language government system falls under the newly credited term of “conversational search,” where the system pays more attention to each word in the query in order to better concur the pages to the meaning of the query rather than a few words. With regards to the changes made to search engine optimization, for content publishers and writers, Hummingbird is intended to resolve issues by getting rid of irrelevant content and spam, allowing Google to develop high-quality content and rely on them to be ‘trusted’ authors.

In October 2019, Google announced they would Begin applying BERT models for English language search queries in the US. Bidirectional Encoder Representations from Transformers (BERT) was another attempt by Google to total their natural language processing, but this era in order to better understand the search queries of their users. In terms of search engine optimization, BERT intended to border users more easily to relevant content and buildup the setting of traffic coming to websites that are ranking in the Search Engine Results Page.

The leading search engines, such as Google, Bing, and Yahoo!, use crawlers to find pages for their algorithmic search results. Pages that are related from supplementary search engine-indexed pages pull off not infatuation to be submitted because they are found automatically. The Yahoo! Directory and DMOZ, two major directories which closed in 2014 and 2017 respectively, both required manual compliance and human editorial review. Google offers Google Search Console, for which an XML Sitemap feed can be created and submitted for pardon to ensure that anything pages are found, especially pages that are not discoverable by automatically in the same way as links in adjunct to their URL consent console. Yahoo! formerly operated a paid compliance service that guaranteed to crawl for a cost per click; however, this practice was discontinued in 2009.

Search engine crawlers may look at a number of substitute factors subsequent to crawling a site. Not every page is indexed by search engines. The set against of pages from the root directory of a site may also be a factor in whether or not pages gain crawled.

Today, most people are searching upon Google using a mobile device. In November 2016, Google announced a major fine-tune to the showing off crawling websites and started to make their index mobile-first, which means the mobile explanation of a fixed idea website becomes the starting narrowing for what Google includes in their index. In May 2019, Google updated the rendering engine of their crawler to be the latest financial credit of Chromium (74 at the period of the announcement). Google indicated that they would regularly update the Chromium rendering engine to the latest version. In December 2019, Google began updating the User-Agent string of their crawler to reflect the latest Chrome explanation used by their rendering service. The come to a close was to allow webmasters mature to update their code that responded to particular bot User-Agent strings. Google ran evaluations and felt confident the impact would be minor.

To avoid undesirable content in the search indexes, webmasters can instruct spiders not to crawl sure files or directories through the customary robots.txt file in the root reference book of the domain. Additionally, a page can be explicitly excluded from a search engine’s database by using a meta tag specific to robots (usually <meta name=”robots” content=”noindex”> ). When a search engine visits a site, the robots.txt located in the root manual is the first file crawled. The robots.txt file is subsequently parsed and will instruct the robot as to which pages are not to be crawled. As a search engine crawler may save a cached copy of this file, it may on occasion crawl pages a webmaster does not wish to crawl. Pages typically prevented from innate crawled improve login-specific pages such as shopping carts and user-specific content such as search results from internal searches. In March 2007, Google warned webmasters that they should prevent indexing of internal search results because those pages are considered search spam. In 2020, Google sunsetted the standard (and open-sourced their code) and now treats it as a relish not a directive. To well enough ensure that pages are not indexed, a page-level robot’s meta tag should be included.

A variety of methods can accumulation the prominence of a webpage within the search results. Cross linking amongst pages of the similar website to have enough money more contacts to important pages may append its visibility. Page design makes users trust a site and desire to stay considering they find it. When people bounce off a site, it counts against the site and affects its credibility.   Writing content that includes frequently searched keyword phrases suitably as to be relevant to a wide variety of search queries will tend to layer traffic. Updating content fittingly as to save search engines crawling back up frequently can give other weight to a site. Adding relevant keywords to a web page’s metadata, including the title tag and meta description, will tend to tally the relevancy of a site’s search listings, thus increasing traffic. URL canonicalization of web pages accessible via compound URLs, using the canonical partner element or via 301 redirects can assist make sure links to swap versions of the URL all count towards the page’s join popularity score. These are known as incoming links, which lessening to the URL and can increase towards the page link’s popularity score, impacting the credibility of a website.

SEO techniques can be classified into two spacious categories: techniques that search engine companies suggest as portion of good design (“white hat”), and those techniques of which search engines get not approve (“black hat”). Search engines attempt to minimize the effect of the latter, among them spamdexing. Industry commentators have classified these methods and the practitioners who hire them as either white cap SEO or black cap SEO. White hats tend to produce results that last a long time, whereas black hats anticipate that their sites may eventually be banned either temporarily or permanently as soon as the search engines discover what they are doing.

An SEO technique is considered a white hat if it conforms to the search engines’ guidelines and involves no deception. As the search engine guidelines are not written as a series of rules or commandments, this is an important distinction to note. White hat SEO is not going on for following guidelines but is virtually ensuring that the content a search engine indexes and in imitation of ranks is the similar content a addict will see. White cap advice is generally summed in the works as creating content for users, not for search engines, and next making that content easily accessible to the online “spider” algorithms, rather than attempting to trick the algorithm from its meant purpose. White cap SEO is in many ways similar to web proceed that promotes accessibility, although the two are not identical.

Black cap SEO attempts to supplement rankings in ways that are disapproved of by the search engines or move deception. One black hat technique uses hidden text, either as text colored similar to the background, in an invisible div, or positioned off-screen. Another method gives a different page depending upon whether the page is beast requested by a human visitor or a search engine, a technique known as cloaking. Another category sometimes used is grey hat SEO. This is in amongst the black cap and white hat approaches, where the methods employed avoid the site instinctive penalized but get not charge in producing the best content for users. Grey hat SEO is certainly focused upon improving search engine rankings.

Search engines may penalize sites they discover using black or grey hat methods, either by reducing their rankings or eliminating their listings from their databases altogether. Such penalties can be applied either automatically by the search engines’ algorithms or by a encyclopedia site review. One example was the February 2006 Google removal of both BMW Germany and Ricoh Germany for the use of deceptive practices. Both companies, however, quickly apologized, fixed the offending pages, and were restored to Google’s search engine results page.

SEO is not an appropriate strategy for all website, and new Internet promotion strategies can be more effective, such as paid advertising through pay-per-click (PPC) campaigns, depending upon the site operator’s goals. Search engine marketing (SEM) is the practice of designing, running, and optimizing search engine ad campaigns. Its difference from SEO is most straightforwardly depicted as the difference in the company of paid and unpaid priority ranking in search results. SEM focuses on prominence more therefore than relevance; website developers should regard SEM subsequent to the utmost importance taking into account consideration to visibility as most navigate to the primary listings of their search. A thriving Internet marketing campaign may next depend upon building high-quality web pages to engage and persuade internet users, setting in the works analytics programs to enable site owners to perform results, and improving a site’s conversion rate. In November 2015, Google released a full 160-page explanation of its Search Quality Rating Guidelines to the public, which revealed a shift in their focus towards “usefulness” and mobile local search. In recent years the mobile broadcast has exploded, overtaking the use of desktops, as shown in by StatCounter in October 2016, where they analyzed 2.5 million websites and found that 51.3% of the pages were loaded by a mobile device. Google has been one of the companies that are utilizing the popularity of mobile usage by encouraging websites to use their Google Search Console, the Mobile-Friendly Test, which allows companies to acquit yourself up their website to the search engine results and determine how reachable their websites are. The closer the keywords are together their ranking will affix based upon key terms.

SEO may generate an suitable return upon investment. However, search engines are not paid for organic search traffic, their algorithms change, and there are no guarantees of continued referrals. Due to this deficiency of guarantee and uncertainty, a matter that relies heavily upon search engine traffic can be anxious major losses if the search engines stop sending visitors. Search engines can bend their algorithms, impacting a website’s search engine ranking, possibly resulting in a enormous loss of traffic. According to Google’s CEO, Eric Schmidt, in 2010, Google made more than 500 algorithm changes – almost 1.5 per day. It is considered a wise concern practice for website operators to liberate themselves from dependence upon search engine traffic. In accessory to accessibility in terms of web crawlers (addressed above), user web accessibility has become increasingly important for SEO.

Optimization techniques are highly tuned to the dominant search engines in the plan market.
The search engines’ market shares revise from publicize to market, as does competition.
In 2003, Danny Sullivan acknowledged that Google represented more or less 75% of anything searches. In markets outdoor the United States, Google’s portion is often larger, and Google remains the dominant search engine worldwide as of 2007. As of 2006, Google had an 85–90% market portion in Germany. While there were hundreds of SEO firms in the US at that time, there were only nearly five in Germany. As of June 2008, the make public share of Google in the UK was close to 90% according to Hitwise. That publicize share is achieved in a number of countries.

As of 2009, there are lonely a few large markets where Google is not the leading search engine. In most cases, when Google is not leading in a given market, it is lagging at the back a local player. The most notable example markets are China, Japan, South Korea, Russia, and the Czech Republic, where respectively Baidu, Yahoo! Japan, Naver, Yandex and Seznam are shout from the rooftops leaders.

Successful search optimization for international markets may require professional translation of web pages, registration of a domain name similar to a summit level domain in the aspire market, and web hosting that provides a local IP address. Otherwise, the fundamental elements of search optimization are in endeavor of fact the same, regardless of language.

On October 17, 2002, SearchKing filed combat in the United States District Court, Western District of Oklahoma, against the search engine Google. SearchKing’s affirmation was that Google’s tactics to prevent spamdexing constituted a tortious interference subsequent to contractual relations. On May 27, 2003, the court contracted Google’s occupation to dismiss the weakness because SearchKing “failed to allow in a claim upon which sustain may be granted.”

In March 2006, KinderStart filed a lawsuit neighboring Google exceeding search engine rankings. KinderStart’s website was removed from Google’s index prior to the lawsuit, and the amount of traffic to the site dropped by 70%. On March 16, 2007, the United States District Court for the Northern District of California (San Jose Division) dismissed KinderStart’s illness without leave to tweak and partially decided Google’s doings for Rule 11 sanctions adjacent to KinderStart’s attorney, requiring him to pay allowance of Google’s authenticated expenses.