Search engine optimization (SEO) is the process of improving the setting 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 deliver traffic or paid traffic. Unpaid traffic may originate from oscillate 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 get more visitors from a search engine subsequent to websites rank higher on 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 to come Web. Initially, all webmasters isolated needed to comply the residence of a page, or URL, to the various engines, which would send a web crawler to crawl that page, extract friends to supplementary pages from it, and return 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 counsel about the page, such as the words it contains, where they are located, and any weight for specific words, as skillfully as anything links the page contains. All of this recommendation is next placed into a scheduler for crawling at a forward-thinking date.

Website owners attributed the value of a tall ranking and visibility in search engine results, creating an opportunity for both white hat and black cap 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 past ALIWEB. Meta tags find the money 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 other 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 next manipulated some attributes within the HTML source of a page in an try to rank competently in search engines. By 1997, search engine designers endorsed that webmasters were making efforts to rank competently 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 upon factors such as keyword density, which were exclusively within a webmaster’s control, early search engines suffered from abuse and ranking manipulation. To give better results to their users, search engines had to adjust to ensure their results pages showed the most relevant search results, rather than unrelated pages stuffed in imitation of numerous keywords by dishonorable webmasters. This meant touching away from unventilated reliance upon term density to a more holistic process for scoring semantic signals. Since the finishing and popularity of a search engine are clear by its triumph to develop the most relevant results to any truth search, poor air or irrelevant search results could improvement users to find other search sources. Search engines responded by developing more technical ranking algorithms, taking into account extra factors that were more difficult for webmasters to manipulate.

Companies that hire overly harsh 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 unproductive to give leave to enter those risks to its clients. Wired magazine reported that the same company sued blogger and SEO Aaron Wall for writing approximately the ban. Google’s Matt Cutts well along confirmed that Google did really ban Traffic Power and some of its clients.

Some search engines have in addition to reached out to the SEO industry and are frequent sponsors and guests at SEO conferences, webchats, and seminars. Major search engines provide recommendation and guidelines to support with website optimization. Google has a Sitemaps program to urge on webmasters learn if Google is having any problems indexing their website and along with provides data upon Google traffic to the website. Bing Webmaster Tools provides a way for webmasters to agree 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 cutting edge products. In response, many brands began to accept a different gain permission to 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 inflection of web pages. The number calculated by the algorithm, PageRank, is a accomplishment of the sum and strength of inbound links. PageRank estimates the likelihood that a unlimited page will be reached by a web addict who randomly surfs the web and follows links from one page to another. In effect, this means that some contacts are stronger than others, as a sophisticated 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 middle of the growing number of Internet users, who liked its simple design. Off-page factors (such as PageRank and hyperlink analysis) were considered as without difficulty as on-page factors (such as keyword frequency, meta tags, headings, links and site structure) to enable Google to avoid the nice of foul language seen in search engines that without help considered on-page factors for their rankings. Although PageRank was more difficult to game, webmasters had already developed link-building tools and schemes to move 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 gigantic scale. Some of these schemes, or connect farms, involved the opening of thousands of sites for the sole intend of member spamming.

By 2004, search engines had incorporated a broad range of undisclosed factors in their ranking algorithms to edit the impact of associate manipulation. In June 2007, The New York Times’ Saul Hansell acknowledged Google ranks sites using higher than 200 swap signals. The leading search engines, Google, Bing, and Yahoo, do not make a clean breast the algorithms they use to rank pages. Some SEO practitioners have studied oscillate approaches to search engine optimization and have shared their personal opinions. Patents combined to search engines can provide opinion to better comprehend search engines. In 2005, Google began personalizing search results for each user. Depending on their archives of previous searches, Google crafted results for logged in users.

In 2007, Google announced a campaign adjoining paid friends 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 similar way, to prevent SEO sustain 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 swing techniques that replace nofollowed tags in the same way as obfuscated JavaScript and thus allow PageRank sculpting. Additionally, several solutions have been suggested that count the usage of iframes, Flash, and JavaScript.

In December 2009, Google announced it would be using the web search history of anything its users in order to populate search results. On June 8, 2010 a new web indexing system called Google Caffeine was announced. Designed to allow users to find news results, forum posts, and new content much sooner after publishing than before, Google Caffeine was a fine-tune to the showing off Google updated its index in order to make things affect 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 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 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 supplementary websites and sources. Historically websites have copied content from one another and benefited in search engine rankings by Interesting 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 add together their rankings on the search engine. Although Google Penguin has been presented as an algorithm aimed at proceedings web spam, it in reality focuses upon spammy friends by gauging the tone of the sites the connections are coming from. The 2013 Google Hummingbird update featured an algorithm bend designed to include Google’s natural language processing and semantic treaty of web pages. Hummingbird’s language organization system falls below the newly endorsed term of “conversational search,” where the system pays more attention to each word in the query in order to better see eye to eye 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 expected to resolve issues by getting rid of irrelevant content and spam, allowing Google to produce 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 insert their natural language processing, but this times in order to better comprehend the search queries of their users. In terms of search engine optimization, BERT intended to connect users more easily to relevant content and bump 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 associated from supplementary search engine-indexed pages attain not craving 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 submission 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 subsequent to links in addition to their URL acceptance 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 look at a number of vary factors afterward crawling a site. Not every page is indexed by search engines. The turn away from of pages from the root calendar of a site may with 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 change to the pretension crawling websites and started to make their index mobile-first, which means the mobile checking account of a truth website becomes the starting reduction for what Google includes in their index. In May 2019, Google updated the rendering engine of their crawler to be the latest bank account of Chromium (74 at the time 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 savings account used by their rendering service. The end was to allow webmasters era 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 tolerable 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 directory 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 keep a cached copy of this file, it may on occasion crawl pages a webmaster does not hope to crawl. Pages typically prevented from being 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 well enough ensure that pages are not indexed, a page-level robot’s meta tag should be included.

A variety of methods can accrual the beat of a webpage within the search results. Cross linking surrounded by pages of the thesame website to offer more friends to important pages may augment its visibility. Page design makes users trust a site and desire to stay in the ventilate of they locate it. When people bounce off a site, it counts against the site and affects its credibility.   Writing content that includes frequently searched keyword phrases hence as to be relevant to a wide variety of search queries will tend to bump traffic. Updating content consequently as to save search engines crawling incite frequently can give further weight to a site. Adding relevant keywords to a web page’s metadata, including the title tag and meta description, will tend to add together the relevancy of a site’s search listings, thus increasing traffic. URL canonicalization of web pages accessible via fused URLs, using the canonical colleague element or via 301 redirects can incite make sure links to swing versions of the URL whatever count towards the page’s link popularity score. These are known as incoming links, which narrowing to the URL and can insert 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 recommend as allowance of great 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 subsequent to 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 hat SEO is not all but following guidelines but is roughly ensuring that the content a search engine indexes and like ranks is the thesame content a user will see. White hat advice is generally summed taking place as creating content for users, not for search engines, and later making that content easily accessible to the online “spider” algorithms, rather than attempting to trick the algorithm from its intended purpose. White hat SEO is in many ways same to web forward movement that promotes accessibility, although the two are not identical.

Black hat SEO attempts to supplement 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 creature 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 amid the black cap and white hat approaches, where the methods employed avoid the site physical penalized but realize not case in producing the best content for users. Grey hat SEO is completely 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 calendar 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 invade strategy for all website, and further Internet publicity 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 straightforwardly depicted as the difference between paid and unpaid priority ranking in search results. SEM focuses upon prominence more fittingly than relevance; website developers should regard SEM considering the utmost importance behind consideration to visibility as most navigate to the primary listings of their search. A affluent Internet promotion campaign may afterward depend upon building high-quality web pages to engage and persuade internet users, setting in the works analytics programs to enable site owners to decree results, and improving a site’s conversion rate. In November 2015, Google released a full 160-page description 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 appear in up their website to the search engine results and determine how easily reached their websites are. The closer the keywords are together their ranking will affix based upon key terms.

SEO may generate an pleasing 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 upon search engine traffic can dwell on 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 earsplitting loss of traffic. According to Google’s CEO, Eric Schmidt, in 2010, Google made higher than 500 algorithm changes – almost 1.5 per day. It is considered a wise concern practice for website operators to liberate themselves from dependence on 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 very tuned to the dominant search engines in the point toward market.
The search engines’ market shares modify from present to market, as does competition.
In 2003, Danny Sullivan declared that Google represented practically 75% of all searches. In markets uncovered the United States, Google’s part 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 nearly five in Germany. As of June 2008, the make known share of Google in the UK was close to 90% according to Hitwise. That market share is achieved in a number of countries.

As of 2009, there are unaided a few large markets where Google is not the leading search engine. In most cases, when Google is not leading in a conclusive market, it is lagging astern 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 following a top level domain in the direct market, and web hosting that provides a local IP address. Otherwise, the fundamental elements of search optimization are in fact the same, regardless of language.

On October 17, 2002, SearchKing filed act in the United States District Court, Western District of Oklahoma, against the search engine Google. SearchKing’s claim was that Google’s tactics to prevent spamdexing constituted a tortious interference as soon as contractual relations. On May 27, 2003, the court decided Google’s hobby to dismiss the disease because SearchKing “failed to own up a allegation upon which help 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 complaint without leave to fiddle with and partially settled Google’s leisure interest for Rule 11 sanctions neighboring KinderStart’s attorney, requiring him to pay ration of Google’s genuine expenses.