Search engine optimization (SEO) is the process of improving the air 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 take up 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 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 taking into consideration websites rank higher upon the search engine results page (SERP). These visitors can then 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 before Web. Initially, all webmasters solitary needed to assent the residence of a page, or URL, to the various engines, which would send a web crawler to crawl that page, extract friends to new pages from it, and compensation information found upon the page to be indexed. The process involves a search engine spider downloading a page and storing it on the search engine’s own server. A second program, known as an indexer, extracts instruction about the page, such as the words it contains, where they are located, and any weight for specific words, as skillfully as whatever links the page contains. All of this instruction is after that placed into a scheduler for crawling at a far along date.

Website owners credited 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 upon webmaster-provided assistance such as the keyword meta tag or index files in engines like ALIWEB. Meta tags allow a guide to each page’s content. Using metadata to index pages was found to be less than reliable, however, because the webmaster’s different 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 moreover manipulated some attributes within the HTML source of a page in an try to rank with ease in search engines. By 1997, search engine designers endorsed 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 once excessive or irrelevant keywords. Early search engines, such as Altavista and Infoseek, adjusted their algorithms to prevent webmasters from manipulating rankings.

By heavily relying on factors such as keyword density, which were exclusively within a webmaster’s control, early search engines suffered from abuse and ranking manipulation. 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 considering numerous keywords by dishonorable webmasters. This meant moving away from heavy reliance upon term density to a more holistic process for scoring semantic signals. Since the talent and popularity of a search engine are certain by its expertise to fabricate the most relevant results to any fixed idea search, poor setting or irrelevant search results could lead users to locate other search sources. Search engines responded by developing more perplexing ranking algorithms, taking into account new factors that were more hard for webmasters to manipulate.

Companies that employ overly severe techniques can gain 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 unsuccessful to state those risks to its clients. Wired magazine reported that the thesame company sued blogger and SEO Aaron Wall for writing nearly the ban. Google’s Matt Cutts superior confirmed that Google did in fact ban Traffic Power and some of its clients.

Some search engines have after that reached out to the SEO industry and are frequent sponsors and guests at SEO conferences, webchats, and seminars. Major search engines provide counsel and guidelines to assist with website optimization. Google has a Sitemaps program to back up webmasters learn if Google is having any problems indexing their website and after that provides data upon Google traffic to the website. Bing Webmaster Tools provides a quirk for webmasters to yield 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 future products. In response, many brands began to accept a different contact 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 on a mathematical algorithm to rate the beat of web pages. The number calculated by the algorithm, PageRank, is a take effect of the quantity and strength of inbound links. PageRank estimates the likelihood that a utter page will be reached by a web addict who randomly surfs the web and follows contacts from one page to another. In effect, this means that some friends are stronger than others, as a far ahead 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 course of the growing number of Internet users, who liked its simple design. Off-page factors (such as PageRank and hyperlink analysis) were considered as well as on-page factors (such as keyword frequency, meta tags, headings, links and site structure) to enable Google to avoid the nice of hurt seen in search engines that only considered on-page factors for their rankings. Although PageRank was more difficult to game, webmasters had already developed link-building tools and schemes to concern 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 colleague farms, involved the foundation of thousands of sites for the sole intention of link spamming.

By 2004, search engines had incorporated a broad range of undisclosed factors in their ranking algorithms to abbreviate the impact of associate manipulation. In June 2007, The New York Times’ Saul Hansell stated Google ranks sites using higher than 200 vary signals. The leading search engines, Google, Bing, and Yahoo, do not declare the algorithms they use to rank pages. Some SEO practitioners have studied swing approaches to search engine optimization and have shared their personal opinions. Patents similar to search engines can provide suggestion to better comprehend 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 adjacent to paid contacts that transfer PageRank. On June 15, 2009, Google disclosed that they had taken proceedings 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 thesame way, to prevent SEO further providers from using nofollow for PageRank sculpting. As a consequences 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 next obfuscated JavaScript and thus permit PageRank sculpting. Additionally, several solutions have been suggested that combine the usage of iframes, Flash, and JavaScript.

In December 2009, Google announced it would be using the web search records of anything its users in order to populate search results. On June 8, 2010 a other web indexing system called Google Caffeine was announced. Designed to permit users to locate news results, forum posts, and new content much sooner after publishing than before, Google Caffeine was a fiddle with to the way Google updated its index in order to make things undertaking up quicker on 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 attempt to make search results more timely and relevant. Historically site administrators have spent months or even years optimizing a website to lump 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 option and benefited in search engine rankings by fascinating in this practice. However, Google implemented a new system that punishes sites whose content is not unique. The 2012 Google Penguin attempted to penalize websites that used manipulative techniques to enhance their rankings on the search engine. Although Google Penguin has been presented as an algorithm aimed at stroke web spam, it in intention of fact focuses on spammy associates by gauging the mood of the sites the connections are coming from. The 2013 Google Hummingbird update featured an algorithm change designed to enlarge Google’s natural language processing and semantic concurrence of web pages. Hummingbird’s language presidency system falls below the newly recognized term of “conversational search,” where the system pays more attention to each word in the query in order to better decide 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 start applying BERT models for English language search queries in the US. Bidirectional Encoder Representations from Transformers (BERT) was another try by Google to affix their natural language processing, but this epoch in order to better comprehend the search queries of their users. In terms of search engine optimization, BERT designed to be stifling to users more easily to relevant content and increase the quality 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 joined from new search engine-indexed pages complete not dependence 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 agreement and human editorial review. Google offers Google Search Console, for which an XML Sitemap feed can be created and submitted for forgive to ensure that anything pages are found, especially pages that are not discoverable by automatically with links in adjunct to their URL agreement console. Yahoo! formerly operated a paid submission service that guaranteed to crawl for a cost per click; however, this practice was discontinued in 2009.

Search engine crawlers may see at a number of every second factors behind crawling a site. Not all page is indexed by search engines. The estrange of pages from the root encyclopedia of a site may as a consequence be a factor in whether or not pages get crawled.

Today, most people are searching upon Google using a mobile device. In November 2016, Google announced a major correct to the pretentiousness crawling websites and started to make their index mobile-first, which means the mobile story of a complete website becomes the starting point 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 times 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 postpone was to permit webmasters get older 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 Definite files or directories through the satisfactory robots.txt file in the root encyclopedia 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 directory is the first file crawled. The robots.txt file is after that parsed and will instruct the machine 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 hope to crawl. Pages typically prevented from instinctive crawled attach 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 adequately ensure that pages are not indexed, a page-level robot’s meta tag should be included.

A variety of methods can layer the emphasis of a webpage within the search results. Cross linking between pages of the same website to come stirring with the maintenance for more friends to important pages may include its visibility. Page design makes users trust a site and want 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 in view of that as to be relevant to a broad variety of search queries will tend to addition traffic. Updating content correspondingly as to keep search engines crawling back up frequently can give extra weight to a site. Adding relevant keywords to a web page’s metadata, including the title tag and meta description, will tend to increase 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 incite make positive links to alternative versions of the URL anything count towards the page’s associate popularity score. These are known as incoming links, which reduction to the URL and can intensify towards the page link’s popularity score, impacting the credibility of a website.

SEO techniques can be classified into two expansive categories: techniques that search engine companies suggest as part of good design (“white hat”), and those techniques of which search engines accomplish 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 build results that last a long time, whereas black hats anticipate that their sites may eventually be banned either temporarily or permanently subsequent to 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 as regards following guidelines but is roughly ensuring that the content a search engine indexes and similar to ranks is the same content a user will see. White hat advice is generally summed taking place as creating content for users, not for search engines, and subsequently making that content easily accessible to the online “spider” algorithms, rather than attempting to trick the algorithm from its intended purpose. White cap SEO is in many ways thesame to web spread that promotes accessibility, although the two are not identical.

Black hat SEO attempts to include rankings in ways that are disapproved of by the search engines or involve deception. One black hat technique uses hidden text, either as text colored thesame to the background, in an invisible div, or positioned off-screen. Another method gives a substitute page depending on whether the page is visceral 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 in the midst of the black hat and white hat approaches, where the methods employed avoid the site innate penalized but reach not deed in producing the best content for users. Grey cap SEO is entirely focused upon improving search engine rankings.

Search engines may penalize sites they discover using black or grey cap 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 directory 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 extra Internet marketing strategies can be more effective, such as paid advertising through pay-per-click (PPC) campaigns, depending on 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 simply depicted as the difference between paid and unpaid priority ranking in search results. SEM focuses on prominence more suitably than relevance; website developers should regard SEM in the same way as the utmost importance in the same way as consideration to visibility as most navigate to the primary listings of their search. A booming Internet promotion campaign may next depend on building high-quality web pages to engage and convince internet users, setting going on analytics programs to enable site owners to fake 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 publicize 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 discharge duty up their website to the search engine results and determine how genial their websites are. The closer the keywords are together their ranking will adjoin based on key terms.

SEO may generate an standard return on 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 nonexistence of guarantee and uncertainty, a issue that relies heavily on search engine traffic can torture yourself major losses if the search engines stop sending visitors. Search engines can fine-tune 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 beyond 500 algorithm changes – almost 1.5 per day. It is considered a wise issue practice for website operators to liberate themselves from dependence upon search engine traffic. In auxiliary to accessibility in terms of web crawlers (addressed above), user web accessibility has become increasingly important for SEO.

Optimization techniques are deeply tuned to the dominant search engines in the aspire market.
The search engines’ market shares revise from push to market, as does competition.
In 2003, Danny Sullivan stated that Google represented not quite 75% of whatever searches. In markets outside 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 share 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 puff share of Google in the UK was near to 90% according to Hitwise. That announce 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 definite market, it is lagging behind 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 make known leaders.

Successful search optimization for international markets may require professional translation of web pages, registration of a domain name in the same way as a summit level domain in the mean 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 war 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 similar to contractual relations. On May 27, 2003, the court granted Google’s action to dismiss the illness because SearchKing “failed to permit a claim upon which minister to may be granted.”

In March 2006, KinderStart filed a lawsuit next to Google beyond 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 sickness without leave to alter and partially decided Google’s hobby for Rule 11 sanctions against KinderStart’s attorney, requiring him to pay ration of Google’s true expenses.