Search engine optimization (SEO) is the process of improving the mood 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 concentrate on traffic or paid traffic. Unpaid traffic may originate from stand-in 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 bearing in mind websites rank higher upon 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 the future Web. Initially, all webmasters lonely needed to give in the dwelling of a page, or URL, to the various engines, which would send a web crawler to crawl that page, extract connections to new pages from it, and reward 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 suggestion about the page, such as the words it contains, where they are located, and any weight for specific words, as competently as all links the page contains. All of this counsel is later placed into a scheduler for crawling at a complex date.

Website owners ascribed 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 in the same way as ALIWEB. Meta tags give a guide to each page’s content. Using metadata to index pages was found to be less than reliable, however, because the webmaster’s substitute of keywords in the meta tag could potentially be an inaccurate representation of the site’s actual content. Flawed data in meta tags, such as those that were not accurate, complete, or falsely attributes, created the potential for pages to be mischaracterized in irrelevant searches.^{[dubious – discuss]} Web content providers then manipulated some attributes within the HTML source of a page in an attempt to rank with ease in search engines. By 1997, search engine designers recognized that webmasters were making efforts to rank well in their search engine and that some webmasters were even manipulating their rankings in search results by stuffing pages gone 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 pay for 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 taking into consideration numerous keywords by unscrupulous webmasters. This meant heartwarming away from oppressive reliance upon term density to a more holistic process for scoring semantic signals. Since the achievement and popularity of a search engine are determined by its capability to build the most relevant results to any pure search, poor atmosphere or irrelevant search results could plus users to find other search sources. Search engines responded by developing more highbrow ranking algorithms, taking into account extra factors that were more hard for webmasters to manipulate.

Companies that hire 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 failed 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 very nearly the ban. Google’s Matt Cutts cutting edge confirmed that Google did in fact ban Traffic Power and some of its clients.

Some search engines have moreover 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 help with website optimization. Google has a Sitemaps program to support webmasters learn if Google is having any problems indexing their website and afterward provides data upon 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 innovative products. In response, many brands began to accept a different retrieve 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 play in of the quantity and strength of inbound links. PageRank estimates the likelihood that a perfect 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 progressive 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 competently as on-page factors (such as keyword frequency, meta tags, headings, links and site structure) to enable Google to avoid the nice of use foul language seen in search engines that without help considered on-page factors for their rankings. Although PageRank was more hard to game, webmasters had already developed link-building tools and schemes to influence the Inktomi search engine, and these methods proved similarly applicable to gaming PageRank. Many sites focus upon exchanging, buying, and selling links, often upon a loud scale. Some of these schemes, or join farms, involved the launch of thousands of sites for the sole direct of join spamming.

By 2004, search engines had incorporated a wide range of undisclosed factors in their ranking algorithms to edit the impact of colleague manipulation. In June 2007, The New York Times’ Saul Hansell declared Google ranks sites using exceeding 200 alternative signals. The leading search engines, Google, Bing, and Yahoo, do not give access the algorithms they use to rank pages. Some SEO practitioners have studied vary approaches to search engine optimization and have shared their personal opinions. Patents partnered to search engines can provide guidance to better understand search engines. In 2005, Google began personalizing search results for each user. Depending upon their chronicles of previous searches, Google crafted results for logged in users.

In 2007, Google announced a campaign against paid associates 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 upon links. Matt Cutts, a well-known software engineer at Google, announced that Google Bot would no longer treat any no follow links, in the similar way, to prevent SEO support providers from using nofollow for PageRank sculpting. As a upshot of this change, the usage of nofollow led to evaporation of PageRank. In order to avoid the above, SEO engineers developed alternating techniques that replace nofollowed tags bearing in mind obfuscated JavaScript and thus permit PageRank sculpting. Additionally, several solutions have been suggested that insert 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 new web indexing system called Google Caffeine was announced. Designed to permit users to locate news results, forum posts, and supplementary content much sooner after publishing than before, Google Caffeine was a amend to the pretentiousness Google updated its index in order to make things measure 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 try to make search results more timely and relevant. Historically site administrators have spent months or even years optimizing a website to buildup search rankings. With the bump 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 substitute 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 tote up their rankings on the search engine. Although Google Penguin has been presented as an algorithm aimed at engagement web spam, it really focuses upon spammy friends by gauging the setting of the sites the links are coming from. The 2013 Google Hummingbird update featured an algorithm fine-tune designed to complement Google’s natural language organization and semantic union of web pages. Hummingbird’s language dispensation system falls under the newly approved term of “conversational search,” where the system pays more attention to each word in the query in order to better have the same opinion the pages to the meaning of the query rather than a few words. With regards to the changes made to search engine optimization, for content publishers and writers, Hummingbird is designed to resolve issues by getting rid of irrelevant content and spam, allowing Google to manufacture 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 attempt by Google to combine their natural language processing, but this get older in order to better understand the search queries of their users. In terms of search engine optimization, BERT designed to be bordering to users more easily to relevant content and deposit 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 united from further search engine-indexed pages pull off not need 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 compliance and human editorial review. Google offers Google Search Console, for which an XML Sitemap feed can be created and submitted for pardon to ensure that whatever pages are found, especially pages that are not discoverable by automatically later links in adjunct to their URL submission 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 see at a number of alternative factors taking into consideration crawling a site. Not all page is indexed by search engines. The distance of pages from the root directory of a site may furthermore be a factor in whether or not pages gain crawled.

Today, most people are searching on Google using a mobile device. In November 2016, Google announced a major amend to the pretentiousness crawling websites and started to make their index mobile-first, which means the mobile description of a conclusive 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 report 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 financial credit used by their rendering service. The come to a close 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 gratifying 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 manual 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 upon occasion crawl pages a webmaster does not hope to crawl. Pages typically prevented from inborn crawled supplement login-specific pages such as shopping carts and user-specific content such as search results from internal searches. In March 2007, Google warned webmasters that they should prevent indexing of internal search results because those pages are considered search spam. In 2020, Google sunsetted the standard (and open-sourced their code) and now treats it as a hint not a directive. To passably 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 amongst pages of the similar website to manage to pay for more associates to important pages may add up its visibility. Page design makes users trust a site and want to stay following they find it. When people bounce off a site, it counts next to the site and affects its credibility.   Writing content that includes frequently searched keyword phrases correspondingly as to be relevant to a broad variety of search queries will tend to layer traffic. Updating content in view of that as to save search engines crawling assist 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 tote up the relevancy of a site’s search listings, thus increasing traffic. URL canonicalization of web pages accessible via merged URLs, using the canonical belong to element or via 301 redirects can back up make determined links to exchange versions of the URL all count towards the page’s associate popularity score. These are known as incoming links, which point to the URL and can complement towards the page link’s popularity score, impacting the credibility of a website.

SEO techniques can be classified into two spacious categories: techniques that search engine companies recommend as share 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 employ them as either white cap SEO or black cap SEO. White hats tend to develop 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 on the subject of following guidelines but is practically ensuring that the content a search engine indexes and behind ranks is the similar content a user will see. White cap advice is generally summed happening 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 meant purpose. White hat SEO is in many ways similar to web expansion that promotes accessibility, although the two are not identical.

Black hat SEO attempts to combine rankings in ways that are disapproved of by the search engines or change 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 rotate page depending upon 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 cap SEO. This is in amongst the black hat and white cap approaches, where the methods employed avoid the site subconscious penalized but complete not accomplishment in producing the best content for users. Grey cap SEO is definitely 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 reference book 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 every website, and supplementary 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 conveniently depicted as the difference between paid and unpaid priority ranking in search results. SEM focuses upon prominence more consequently than relevance; website developers should regard SEM following the utmost importance in the same way as consideration to visibility as most navigate to the primary listings of their search. A well-to-do Internet publicity campaign may with depend upon building high-quality web pages to engage and convince internet users, setting stirring analytics programs to enable site owners to do its stuff results, and improving a site’s conversion rate. In November 2015, Google released a full 160-page bank account 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 bill up their website to the search engine results and determine how clear their websites are. The closer the keywords are together their ranking will swell based upon key terms.

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

Optimization techniques are terribly tuned to the dominant search engines in the objective market.
The search engines’ market shares change from puff to market, as does competition.
In 2003, Danny Sullivan stated that Google represented not quite 75% of all searches. In markets outdoor 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 ration in Germany. While there were hundreds of SEO firms in the US at that time, there were only virtually five in Germany. As of June 2008, the make public 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 unaccompanied a few large markets where Google is not the leading search engine. In most cases, when Google is not leading in a utter 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 puff leaders.

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

On October 17, 2002, SearchKing filed stroke in the United States District Court, Western District of Oklahoma, against the search engine Google. SearchKing’s allegation was that Google’s tactics to prevent spamdexing constituted a tortious interference in the same way as contractual relations. On May 27, 2003, the court decided Google’s motion to dismiss the complaint because SearchKing “failed to make a clean breast a allegation upon which sustain may be granted.”

In March 2006, KinderStart filed a lawsuit next to Google greater 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 sickness without depart to modify and partially granted Google’s motion for Rule 11 sanctions next to KinderStart’s attorney, requiring him to pay ration of Google’s legal expenses.