Search engine optimization (SEO) is the process of improving the environment and quantity 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 focus on traffic or paid traffic. Unpaid traffic may originate from alternative kinds of searches, including image search, video search, academic search, news search, and industry-specific vertical search engines.

As an Internet marketing 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 bearing in mind websites rank higher upon the search engine results page (SERP). These visitors can later 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 the future Web. Initially, all webmasters isolated needed to assent the house of a page, or URL, to the various engines, which would send a web crawler to crawl that page, extract connections to supplementary 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 opinion about the page, such as the words it contains, where they are located, and any weight for specific words, as with ease as everything links the page contains. All of this instruction is subsequently placed into a scheduler for crawling at a cutting edge date.

Website owners credited the value of a tall ranking and visibility in search engine results, creating an opportunity for both white hat 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 suggestion such as the keyword meta tag or index files in engines subsequent to ALIWEB. Meta tags have the funds for a guide to each page’s content. Using metadata to index pages was found to be less than reliable, however, because the webmaster’s substitute 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 then manipulated some attributes within the HTML source of a page in an attempt to rank competently in search engines. By 1997, search engine designers certified that webmasters were making efforts to rank capably in their search engine and that some webmasters were even manipulating their rankings in search results by stuffing pages with 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 manage to pay for better results to their users, search engines had to accustom yourself to ensure their results pages showed the most relevant search results, rather than unrelated pages stuffed when numerous keywords by unprincipled webmasters. This meant disturbing away from close reliance upon term density to a more holistic process for scoring semantic signals. Since the skill and popularity of a search engine are certain by its achievement to fabricate the most relevant results to any complete search, poor character or irrelevant search results could benefit users to find other search sources. Search engines responded by developing more complex ranking algorithms, taking into account supplementary factors that were more hard for webmasters to manipulate.

Companies that employ overly prickly techniques can get their client websites banned from the search results. In 2005, the Wall Street Journal reported upon a company, Traffic Power, which allegedly used high-risk techniques and bungled to let pass those risks to its clients. Wired magazine reported that the same company sued blogger and SEO Aaron Wall for writing virtually the ban. Google’s Matt Cutts forward-looking confirmed that Google did in reality ban Traffic Power and some of its clients.

Some search engines have next reached out to the SEO industry and are frequent sponsors and guests at SEO conferences, webchats, and seminars. Major search engines provide suggestion and guidelines to back up with website optimization. Google has a Sitemaps program to help webmasters learn if Google is having any problems indexing their website and as a consequence provides data upon Google traffic to the website. Bing Webmaster Tools provides a artifice for webmasters to assent 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 difficult products. In response, many brands began to take a different edit to their Internet marketing 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 emphasis 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 unqualified page will be reached by a web addict who randomly surfs the web and follows friends from one page to another. In effect, this means that some friends are stronger than others, as a superior PageRank page is more likely to be reached by the random web surfer.

Page and Brin founded Google in 1998. Google attracted a loyal following in the midst of the growing number of Internet users, who liked its easy 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 treat badly seen in search engines that lonesome considered on-page factors for their rankings. Although PageRank was more difficult 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 on exchanging, buying, and selling links, often upon a huge scale. Some of these schemes, or member farms, involved the establishment of thousands of sites for the sole aspire of link spamming.

By 2004, search engines had incorporated a broad range of undisclosed factors in their ranking algorithms to abbreviate the impact of colleague manipulation. In June 2007, The New York Times’ Saul Hansell confirmed Google ranks sites using greater than 200 vary signals. The leading search engines, Google, Bing, and Yahoo, do not state the algorithms they use to rank pages. Some SEO practitioners have studied every second approaches to search engine optimization and have shared their personal opinions. Patents united to search engines can provide guidance to better comprehend search engines. In 2005, Google began personalizing search results for each user. Depending upon their history of previous searches, Google crafted results for logged in users.

In 2007, Google announced a campaign adjacent to paid contacts that transfer PageRank. On June 15, 2009, Google disclosed that they had taken events to mitigate the effects of PageRank sculpting by use of the nofollow attribute on links. Matt Cutts, a renowned software engineer at Google, announced that Google Bot would no longer treat any no follow links, in the thesame way, to prevent SEO serve providers from using nofollow for PageRank sculpting. As a upshot of this change, the usage of nofollow led to evaporation of PageRank. In order to avoid the above, SEO engineers developed alternative techniques that replace nofollowed tags gone obfuscated JavaScript and thus allow PageRank sculpting. Additionally, several solutions have been suggested that improve the usage of iframes, Flash, and JavaScript.

In December 2009, Google announced it would be using the web search records of whatever its users in order to populate search results. On June 8, 2010 a new web indexing system called Google Caffeine was announced. Designed to permit users to find news results, forum posts, and extra content much sooner after publishing than before, Google Caffeine was a regulate to the pretentiousness Google updated its index in order to make things pretense 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 increase search rankings. With the deposit in popularity of social media sites and blogs, the leading engines made changes to their algorithms to permit 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 unusual and benefited in search engine rankings by engaging in this practice. However, Google implemented a supplementary system that punishes sites whose content is not unique. The 2012 Google Penguin attempted to penalize websites that used manipulative techniques to add up their rankings on the search engine. Although Google Penguin has been presented as an algorithm aimed at feat web spam, it truly focuses on spammy connections by gauging the environment of the sites the connections are coming from. The 2013 Google Hummingbird update featured an algorithm alter designed to enhance Google’s natural language doling out and semantic contract of web pages. Hummingbird’s language dealing out system falls below the newly approved term of “conversational search,” where the system pays more attention to each word in the query in order to better be consistent with 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 designed to resolve issues by getting rid of irrelevant content and spam, allowing Google to fabricate high-quality content and rely on them to be ‘trusted’ authors.

In October 2019, Google announced they would start applying BERT models for English language search queries in the US. Bidirectional Encoder Representations from Transformers (BERT) was another attempt by Google to tote up their natural language processing, but this period in order to better comprehend the search queries of their users. In terms of search engine optimization, BERT intended to border users more easily to relevant content and bump the environment 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 locate pages for their algorithmic search results. Pages that are joined from further search engine-indexed pages realize not obsession 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 consent and human editorial review. Google offers Google Search Console, for which an XML Sitemap feed can be created and submitted for release to ensure that anything pages are found, especially pages that are not discoverable by automatically when links in supplement to their URL assent console. Yahoo! formerly operated a paid consent 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 alternative factors when crawling a site. Not every page is indexed by search engines. The make unfriendly of pages from the root encyclopedia of a site may furthermore be a factor in whether or not pages gain crawled.

Today, most people are searching on Google using a mobile device. In November 2016, Google announced a major regulate to the quirk crawling websites and started to make their index mobile-first, which means the mobile explanation of a truth website becomes the starting dwindling for what Google includes in their index. In May 2019, Google updated the rendering engine of their crawler to be the latest relation of Chromium (74 at the get older 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 bill used by their rendering service. The put off was to allow webmasters time 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 distinct files or directories through the okay 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 encyclopedia is the first file crawled. The robots.txt file is after that 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 upon occasion crawl pages a webmaster does not hope to crawl. Pages typically prevented from inborn crawled enhance 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 hint 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 deposit the prominence of a webpage within the search results. Cross linking in the midst of pages of the thesame website to have enough money more links to important pages may tally up its visibility. Page design makes users trust a site and want to stay taking into consideration they find it. When people bounce off a site, it counts adjacent to the site and affects its credibility.   Writing content that includes frequently searched keyword phrases appropriately as to be relevant to a broad variety of search queries will tend to lump traffic. Updating content thus as to keep search engines crawling assist 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 up the relevancy of a site’s search listings, thus increasing traffic. URL canonicalization of web pages accessible via multiple URLs, using the canonical associate element or via 301 redirects can back make sure links to exchange versions of the URL everything count towards the page’s colleague popularity score. These are known as incoming links, which dwindling 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 recommend as allocation of good design (“white hat”), and those techniques of which search engines do 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 employ them as either white hat SEO or black cap SEO. White hats tend to manufacture results that last a long time, whereas black hats anticipate that their sites may eventually be banned either temporarily or permanently behind the search engines discover what they are doing.

An SEO technique is considered a white cap 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 cap SEO is not roughly following guidelines but is virtually ensuring that the content a search engine indexes and taking into consideration ranks is the thesame content a user will see. White cap advice is generally summed stirring as creating content for users, not for search engines, and after that making that content easily accessible to the online “spider” algorithms, rather than attempting to trick the algorithm from its meant purpose. White hat SEO is in many ways thesame to web loan that promotes accessibility, although the two are not identical.

Black cap SEO attempts to append rankings in ways that are disapproved of by the search engines or move deception. One black cap technique uses hidden text, either as text colored same to the background, in an invisible div, or positioned off-screen. Another method gives a substitute page depending on whether the page is brute requested by a human visitor or a search engine, a technique known as cloaking. Another category sometimes used is grey cap SEO. This is in between the black cap and white hat approaches, where the methods employed avoid the site creature penalized but reach not battle in producing the best content for users. Grey cap SEO is very focused on 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 seize strategy for every website, and supplementary 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 understandably depicted as the difference with paid and unpaid priority ranking in search results. SEM focuses upon prominence more suitably than relevance; website developers should regard SEM in the same way as the utmost importance in the tune of consideration to visibility as most navigate to the primary listings of their search. A affluent Internet promotion campaign may as well as depend upon building high-quality web pages to engage and convince internet users, setting in the works analytics programs to enable site owners to feint results, and improving a site’s conversion rate. In November 2015, Google released a full 160-page balance 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 puff 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 enactment up their website to the search engine results and determine how to hand their websites are. The closer the keywords are together their ranking will insert based upon key terms.

SEO may generate an enjoyable 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 suffer major losses if the search engines stop sending visitors. Search engines can regulate their algorithms, impacting a website’s search engine ranking, possibly resulting in a great loss of traffic. According to Google’s CEO, Eric Schmidt, in 2010, Google made exceeding 500 algorithm changes – almost 1.5 per day. It is considered a wise event practice for website operators to liberate themselves from dependence on search engine traffic. In complement to accessibility in terms of web crawlers (addressed above), user web accessibility has become increasingly important for SEO.

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

As of 2009, there are only a few large markets where Google is not the leading search engine. In most cases, when Google is not leading in a unadulterated 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 puff leaders.

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

On October 17, 2002, SearchKing filed dogfight 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 in the same way as contractual relations. On May 27, 2003, the court contracted Google’s action to dismiss the weakness because SearchKing “failed to welcome a affirmation upon which serve may be granted.”

In March 2006, KinderStart filed a lawsuit next to Google more than 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 disease without depart to fine-tune and partially approved Google’s leisure interest for Rule 11 sanctions neighboring KinderStart’s attorney, requiring him to pay ration of Google’s real expenses.