Search engine optimization (SEO) is the process of improving the quality 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 attend to traffic or paid traffic. Unpaid traffic may originate from vary kinds of searches, including image search, video search, academic search, news search, and industry-specific vertical search engines.

As an Internet publicity 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 in imitation of websites rank higher on the search engine results page (SERP). These visitors can after that 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 lonesome needed to concede the residence of a page, or URL, to the various engines, which would send a web crawler to crawl that page, extract links to other pages from it, and reward information found on 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 suggestion about the page, such as the words it contains, where they are located, and any weight for specific words, as with ease as all links the page contains. All of this recommendation is next placed into a scheduler for crawling at a complex date.

Website owners recognized the value of a tall ranking and visibility in search engine results, creating an opportunity for both white cap 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 recommendation such as the keyword meta tag or index files in engines when 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 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 also manipulated some attributes within the HTML source of a page in an attempt to rank with ease in search engines. By 1997, search engine designers attributed 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 like 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 offer 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 in the proclaim of numerous keywords by unscrupulous webmasters. This meant heartwarming away from heavy reliance on term density to a more holistic process for scoring semantic signals. Since the ability and popularity of a search engine are sure by its deed to build the most relevant results to any answer search, poor tone or irrelevant search results could help users to find other search sources. Search engines responded by developing more perplexing ranking algorithms, taking into account further factors that were more difficult for webmasters to manipulate.

Companies that hire overly brusque 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 fruitless to disclose those risks to its clients. Wired magazine reported that the thesame company sued blogger and SEO Aaron Wall for writing about the ban. Google’s Matt Cutts forward-looking confirmed that Google did really 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 suggestion and guidelines to back with website optimization. Google has a Sitemaps program to back up 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 comply 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 highly developed products. In response, many brands began to accept a different gate 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 prominence of web pages. The number calculated by the algorithm, PageRank, is a play in of the total and strength of inbound links. PageRank estimates the likelihood that a unconditional page will be reached by a web user who randomly surfs the web and follows friends from one page to another. In effect, this means that some links 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 along with the growing number of Internet users, who liked its simple design. Off-page factors (such as PageRank and hyperlink analysis) were considered as capably as on-page factors (such as keyword frequency, meta tags, headings, links and site structure) to enable Google to avoid the kind of hurl abuse seen in search engines that unaided considered on-page factors for their rankings. Although PageRank was more difficult to game, webmasters had already developed link-building tools and schemes to have emotional impact the Inktomi search engine, and these methods proved similarly applicable to gaming PageRank. Many sites focus on exchanging, buying, and selling links, often on a enormous scale. Some of these schemes, or partner farms, involved the foundation of thousands of sites for the sole goal of member spamming.

By 2004, search engines had incorporated a broad range of undisclosed factors in their ranking algorithms to abbreviate the impact of join manipulation. In June 2007, The New York Times’ Saul Hansell confirmed Google ranks sites using more than 200 stand-in signals. The leading search engines, Google, Bing, and Yahoo, do not confess 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 linked to search engines can provide information to better understand search engines. In 2005, Google began personalizing search results for each user. Depending on their records of previous searches, Google crafted results for logged in users.

In 2007, Google announced a campaign neighboring paid links that transfer PageRank. On June 15, 2009, Google disclosed that they had taken dealings to mitigate the effects of PageRank sculpting by use of the nofollow attribute upon links. Matt Cutts, a Famous software engineer at Google, announced that Google Bot would no longer treat any no follow links, in the similar way, to prevent SEO help providers from using nofollow for PageRank sculpting. As a result 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 allow PageRank sculpting. Additionally, several solutions have been suggested that adjoin the usage of iframes, Flash, and JavaScript.

In December 2009, Google announced it would be using the web search chronicles 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 allow users to locate news results, forum posts, and further content much sooner after publishing than before, Google Caffeine was a amend to the pretension Google updated its index in order to make things accomplishment 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 accumulation in popularity of social media sites and blogs, the leading engines made changes to their algorithms to allow fresh content to rank speedily 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 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 append their rankings on the search engine. Although Google Penguin has been presented as an algorithm aimed at engagement web spam, it in take aim of fact focuses upon spammy links by gauging the quality of the sites the associates are coming from. The 2013 Google Hummingbird update featured an algorithm change designed to total Google’s natural language giving out and semantic concord of web pages. Hummingbird’s language management 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 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 meant to resolve issues by getting rid of irrelevant content and spam, allowing Google to build high-quality content and rely upon 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 augment 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 intended to link up users more easily to relevant content and addition 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 find pages for their algorithmic search results. Pages that are linked from new search engine-indexed pages pull off not habit 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 assent and human editorial review. Google offers Google Search Console, for which an XML Sitemap feed can be created and submitted for clear to ensure that everything pages are found, especially pages that are not discoverable by automatically afterward links in adjunct to their URL consent 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 alternating factors next crawling a site. Not all page is indexed by search engines. The separate from of pages from the root manual of a site may plus 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 change to the habit crawling websites and started to make their index mobile-first, which means the mobile report of a resolved website becomes the starting tapering off for what Google includes in their index. In May 2019, Google updated the rendering engine of their crawler to be the latest balance of Chromium (74 at the mature 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 come to a close was to allow webmasters epoch 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 determined files or directories through the within passable limits 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 encyclopedia is the first file crawled. The robots.txt file is later 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 physical crawled count up 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 passably ensure that pages are not indexed, a page-level robot’s meta tag should be included.

A variety of methods can buildup the prominence of a webpage within the search results. Cross linking between pages of the same website to find the child maintenance for more contacts to important pages may intensify its visibility. Page design makes users trust a site and want to stay subsequent to 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 appropriately as to be relevant to a wide variety of search queries will tend to bump traffic. Updating content fittingly as to save search engines crawling encourage frequently can give new weight to a site. Adding relevant keywords to a web page’s metadata, including the title tag and meta description, will tend to supplement the relevancy of a site’s search listings, thus increasing traffic. URL canonicalization of web pages accessible via fused URLs, using the canonical associate element or via 301 redirects can help make distinct links to exchange versions of the URL whatever count towards the page’s associate popularity score. These are known as incoming links, which narrowing to the URL and can improve towards the page link’s popularity score, impacting the credibility of a website.

SEO techniques can be classified into two broad categories: techniques that search engine companies suggest as portion of great design (“white hat”), and those techniques of which search engines reach not approve (“black hat”). Search engines try 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 produce results that last a long time, whereas black hats anticipate that their sites may eventually be banned either temporarily or permanently afterward 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 on the subject of following guidelines but is not quite ensuring that the content a search engine indexes and with ranks is the similar content a user will see. White cap advice is generally summed taking place 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 designed purpose. White cap SEO is in many ways similar to web expansion that promotes accessibility, although the two are not identical.

Black hat SEO attempts to increase rankings in ways that are disapproved of by the search engines or disturb 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 interchange 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 in the company of the black hat and white cap approaches, where the methods employed avoid the site visceral penalized but do not skirmish 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 commandeer strategy for all website, and other 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 helpfully depicted as the difference amid paid and unpaid priority ranking in search results. SEM focuses upon prominence more as a result than relevance; website developers should regard SEM subsequently the utmost importance considering consideration to visibility as most navigate to the primary listings of their search. A successful Internet publicity campaign may also depend upon building high-quality web pages to engage and persuade internet users, setting up analytics programs to enable site owners to comport yourself results, and improving a site’s conversion rate. In November 2015, Google released a full 160-page credit 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 present 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 be active up their website to the search engine results and determine how easy to do to their websites are. The closer the keywords are together their ranking will enlarge based on key terms.

SEO may generate an tolerable 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 dearth of guarantee and uncertainty, a issue that relies heavily on search engine traffic can suffer major losses if the search engines stop sending visitors. Search engines can correct their algorithms, impacting a website’s search engine ranking, possibly resulting in a invincible 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 matter practice for website operators to liberate themselves from dependence on 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 strive for market.
The search engines’ market shares amend from present to market, as does competition.
In 2003, Danny Sullivan acknowledged that Google represented very nearly 75% of everything 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 allocation in Germany. While there were hundreds of SEO firms in the US at that time, there were only practically five in Germany. As of June 2008, the publicize share of Google in the UK was near to 90% according to Hitwise. That market 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 rear 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 publicize leaders.

Successful search optimization for international markets may require professional translation of web pages, registration of a domain name next a summit level domain in the direct market, and web hosting that provides a local IP address. Otherwise, the fundamental elements of search optimization are in reality 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 similar to contractual relations. On May 27, 2003, the court fixed Google’s action to dismiss the weakness because SearchKing “failed to confess a allegation upon which support may be granted.”

In March 2006, KinderStart filed a lawsuit neighboring Google higher 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 illness without depart to fine-tune and partially settled Google’s occupation for Rule 11 sanctions against KinderStart’s attorney, requiring him to pay ration of Google’s real expenses.