Search engine optimization (SEO) is the process of improving the setting and sum 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 tackle traffic or paid traffic. Unpaid traffic may originate from substitute 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 with websites rank higher on the search engine results page (SERP). These visitors can subsequently 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 into the future Web. Initially, all webmasters lonely needed to yield the address of a page, or URL, to the various engines, which would send a web crawler to crawl that page, extract connections to other 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 upon 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 without difficulty as all links the page contains. All of this recommendation is later placed into a scheduler for crawling at a forward-thinking date.

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

Early versions of search algorithms relied on webmaster-provided assistance such as the keyword meta tag or index files in engines afterward 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 out of the ordinary 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 furthermore manipulated some attributes within the HTML source of a page in an try to rank well in search engines. By 1997, search engine designers credited 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 subsequently 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 become accustomed to ensure their results pages showed the most relevant search results, rather than unrelated pages stuffed subsequent to numerous keywords by dishonorable webmasters. This meant distressing away from oppressive reliance on term density to a more holistic process for scoring semantic signals. Since the achievement and popularity of a search engine are sure by its expertise to fabricate the most relevant results to any pure search, poor character or irrelevant search results could help users to find other search sources. Search engines responded by developing more rarefied ranking algorithms, taking into account extra factors that were more hard for webmasters to manipulate.

Companies that employ overly harsh 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 futile to permit those risks to its clients. Wired magazine reported that the similar company sued blogger and SEO Aaron Wall for writing not quite the ban. Google’s Matt Cutts forward-thinking confirmed that Google did in reality ban Traffic Power and some of its clients.

Some search engines have afterward reached out to the SEO industry and are frequent sponsors and guests at SEO conferences, webchats, and seminars. Major search engines provide assistance 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 afterward provides data on Google traffic to the website. Bing Webmaster Tools provides a showing off for webmasters to concur 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 forward-thinking products. In response, many brands began to accept a different entry to their Internet publicity 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 feat of the total and strength of inbound links. PageRank estimates the likelihood that a truth page will be reached by a web addict who randomly surfs the web and follows connections from one page to another. In effect, this means that some connections are stronger than others, as a progressive PageRank page is more likely to be reached by the random web surfer.

Page and Brin founded Google in 1998. Google attracted a loyal 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 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 invective seen in search engines that unaccompanied considered on-page factors for their rankings. Although PageRank was more hard to game, webmasters had already developed link-building tools and schemes to shape 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 invincible scale. Some of these schemes, or link farms, involved the start of thousands of sites for the sole want of associate spamming.

By 2004, search engines had incorporated a wide range of undisclosed factors in their ranking algorithms to cut the impact of join manipulation. In June 2007, The New York Times’ Saul Hansell acknowledged Google ranks sites using beyond 200 alternating signals. The leading search engines, Google, Bing, and Yahoo, do not give leave to enter 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 linked to search engines can provide counsel to better understand 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 neighboring paid links 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 upon links. Matt Cutts, a Famous software engineer at Google, announced that Google Bot would no longer treat any no follow links, in the thesame way, to prevent SEO relieve providers from using nofollow for PageRank sculpting. As a outcome of this change, the usage of nofollow led to evaporation of PageRank. In order to avoid the above, SEO engineers developed alternating techniques that replace nofollowed tags in the appearance of obfuscated JavaScript and thus allow PageRank sculpting. Additionally, several solutions have been suggested that add up 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 find news results, forum posts, and new content much sooner after publishing than before, Google Caffeine was a fiddle with to the pretension Google updated its index in order to make things law 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 growth search rankings. With the bump 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 additional 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 other system that punishes sites whose content is not unique. The 2012 Google Penguin attempted to penalize websites that used manipulative techniques to increase their rankings upon the search engine. Although Google Penguin has been presented as an algorithm aimed at act web spam, it in reality focuses upon spammy contacts by gauging the quality of the sites the connections are coming from. The 2013 Google Hummingbird update featured an algorithm alter designed to enhance Google’s natural language paperwork and semantic covenant of web pages. Hummingbird’s language executive system falls under the newly attributed term of “conversational search,” where the system pays more attention to each word in the query in order to better grant 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 produce high-quality content and rely upon them to be ‘trusted’ authors.

In October 2019, Google announced they would Begin applying BERT models for English language search queries in the US. Bidirectional Encoder Representations from Transformers (BERT) was another try by Google to augment their natural language processing, but this epoch in order to better understand the search queries of their users. In terms of search engine optimization, BERT meant to be muggy to users more easily to relevant content and lump 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 locate pages for their algorithmic search results. Pages that are linked from supplementary search engine-indexed pages realize 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 release to ensure that everything pages are found, especially pages that are not discoverable by automatically behind links in complement to their URL compliance console. Yahoo! formerly operated a paid acceptance 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 different factors later than crawling a site. Not all page is indexed by search engines. The distance of pages from the root reference book of a site may with be a factor in whether or not pages gain crawled.

Today, most people are searching upon Google using a mobile device. In November 2016, Google announced a major fiddle with to the way crawling websites and started to make their index mobile-first, which means the mobile report of a answer website becomes the starting lessening 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 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 version used by their rendering service. The defer was to permit 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 clear files or directories through the enjoyable robots.txt file in the root calendar 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 next 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 wish to crawl. Pages typically prevented from innate crawled improve login-specific pages such as shopping carts and user-specific content such as search results from internal searches. In March 2007, Google warned webmasters that they should prevent indexing of internal search results because those pages are considered search spam. In 2020, Google sunsetted the standard (and open-sourced their code) and now treats it as a relish not a directive. To suitably ensure that pages are not indexed, a page-level robot’s meta tag should be included.

A variety of methods can addition the stress of a webpage within the search results. Cross linking amongst pages of the similar website to meet the expense of more links to important pages may count its visibility. Page design makes users trust a site and desire to stay once they locate it. When people bounce off a site, it counts neighboring the site and affects its credibility.   Writing content that includes frequently searched keyword phrases in view of that as to be relevant to a wide variety of search queries will tend to bump traffic. Updating content therefore as to save search engines crawling put stirring to frequently can give supplementary weight to a site. Adding relevant keywords to a web page’s metadata, including the title tag and meta description, will tend to count up the relevancy of a site’s search listings, thus increasing traffic. URL canonicalization of web pages accessible via combined URLs, using the canonical join element or via 301 redirects can put going on to make clear links to alternative 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 count 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 portion 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 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 as soon as the search engines discover what they are doing.

An SEO technique is considered a white hat if it conforms to the search engines’ guidelines and involves no deception. As the search engine guidelines are not written as a series of rules or commandments, this is an important distinction to note. White cap SEO is not more or less following guidelines but is nearly ensuring that the content a search engine indexes and as soon as ranks is the thesame content a addict will see. White cap advice is generally summed occurring 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 expected purpose. White cap SEO is in many ways thesame to web early payment that promotes accessibility, although the two are not identical.

Black hat SEO attempts to insert rankings in ways that are disapproved of by the search engines or shape deception. One black cap technique uses hidden text, either as text colored similar to the background, in an invisible div, or positioned off-screen. Another method gives a swing page depending on whether the page is innate 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 surrounded by the black cap and white cap approaches, where the methods employed avoid the site mammal penalized but complete not exploit in producing the best content for users. Grey cap SEO is utterly 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 manual site review. One example was the February 2006 Google removal of both BMW Germany and Ricoh Germany for the use of deceptive practices. Both companies, however, quickly apologized, fixed the offending pages, and were restored to Google’s search engine results page.

SEO is not an appropriate strategy for every website, and extra Internet publicity 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 clearly depicted as the difference in the middle of paid and unpaid priority ranking in search results. SEM focuses on prominence more for that reason than relevance; website developers should regard SEM subsequently the utmost importance later than consideration to visibility as most navigate to the primary listings of their search. A wealthy Internet promotion campaign may next depend on building high-quality web pages to engage and convince internet users, setting happening analytics programs to enable site owners to accomplishment 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 shout from the rooftops 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 exploit 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 tolerable 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 nonattendance of guarantee and uncertainty, a business that relies heavily on search engine traffic can be anxious 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 all-powerful 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 matter practice for website operators to liberate themselves from dependence on search engine traffic. In supplement 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 wish market.
The search engines’ market shares rework from shout out to market, as does competition.
In 2003, Danny Sullivan stated that Google represented just about 75% of anything searches. In markets outdoor the United States, Google’s allowance 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 just about five in Germany. As of June 2008, the publicize share of Google in the UK was near to 90% according to Hitwise. That push share is achieved in a number of countries.

As of 2009, there are without help a few large markets where Google is not the leading search engine. In most cases, when Google is not leading in a unconditional 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 make known leaders.

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

On October 17, 2002, SearchKing filed encounter 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 when contractual relations. On May 27, 2003, the court approved Google’s movement to dismiss the disease because SearchKing “failed to let pass a claim upon which minister to may be granted.”

In March 2006, KinderStart filed a lawsuit adjacent to 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 disorder without leave to modify and partially granted Google’s motion for Rule 11 sanctions against KinderStart’s attorney, requiring him to pay portion of Google’s true expenses.