Search engine optimization (SEO) is the process of improving the tone and quantity of website traffic to a website or a web page from search engines. SEO targets unpaid traffic (known as “natural” or “organic” results) rather than forward 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 bearing in mind websites rank higher upon the search engine results page (SERP). These visitors can next 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 early Web. Initially, all webmasters lonesome needed to give in the quarters of a page, or URL, to the various engines, which would send a web crawler to crawl that page, extract links to further pages from it, and return 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 information about the page, such as the words it contains, where they are located, and any weight for specific words, as well as all links the page contains. All of this guidance is after that placed into a scheduler for crawling at a well along date.

Website owners official 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 upon webmaster-provided opinion such as the keyword meta tag or index files in engines past ALIWEB. Meta tags come stirring with the child maintenance 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 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 with manipulated some attributes within the HTML source of a page in an attempt to rank skillfully in search engines. By 1997, search engine designers credited that webmasters were making efforts to rank with ease in their search engine and that some webmasters were even manipulating their rankings in search results by stuffing pages later 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 meet the expense of better results to their users, search engines had to familiarize to ensure their results pages showed the most relevant search results, rather than unrelated pages stuffed bearing in mind numerous keywords by unprincipled webmasters. This meant disturbing away from close reliance on term density to a more holistic process for scoring semantic signals. Since the talent and popularity of a search engine are positive by its capability to build the most relevant results to any fixed search, poor tone or irrelevant search results could benefit users to locate other search sources. Search engines responded by developing more technical ranking algorithms, taking into account additional factors that were more difficult for webmasters to manipulate.

Companies that hire overly rough techniques can gain 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 failed to come clean those risks to its clients. Wired magazine reported that the thesame company sued blogger and SEO Aaron Wall for writing approximately the ban. Google’s Matt Cutts far along confirmed that Google did really 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 guidance and guidelines to assist with website optimization. Google has a Sitemaps program to assist webmasters learn if Google is having any problems indexing their website and also provides data upon Google traffic to the website. Bing Webmaster Tools provides a habit 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 future products. In response, many brands began to accept a different door 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 on a mathematical algorithm to rate the beat of web pages. The number calculated by the algorithm, PageRank, is a play of the total and strength of inbound links. PageRank estimates the likelihood that a supreme page will be reached by a web addict 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 highly developed 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 midst 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 kind of exploitation seen in search engines that unaccompanied considered on-page factors for their rankings. Although PageRank was more difficult to game, webmasters had already developed link-building tools and schemes to distress 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 omnipresent scale. Some of these schemes, or connect farms, involved the foundation of thousands of sites for the sole take aim of connect spamming.

By 2004, search engines had incorporated a wide range of undisclosed factors in their ranking algorithms to reduce the impact of join manipulation. In June 2007, The New York Times’ Saul Hansell acknowledged Google ranks sites using greater than 200 exchange signals. The leading search engines, Google, Bing, and Yahoo, do not welcome the algorithms they use to rank pages. Some SEO practitioners have studied swap approaches to search engine optimization and have shared their personal opinions. Patents connected 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 adjoining 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 renowned software engineer at Google, announced that Google Bot would no longer treat any no follow links, in the thesame way, to prevent SEO give support to 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 every second techniques that replace nofollowed tags in imitation of obfuscated JavaScript and thus allow PageRank sculpting. Additionally, several solutions have been suggested that increase the usage of iframes, Flash, and JavaScript.

In December 2009, Google announced it would be using the web search chronicles of everything its users in order to populate search results. On June 8, 2010 a additional web indexing system called Google Caffeine was announced. Designed to permit users to find news results, forum posts, and new content much sooner after publishing than before, Google Caffeine was a alter to the pretentiousness Google updated its index in order to make things perform 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 mass 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 other websites and sources. Historically websites have copied content from one unorthodox and benefited in search engine rankings by engaging in this practice. However, Google implemented a further system that punishes sites whose content is not unique. The 2012 Google Penguin attempted to penalize websites that used manipulative techniques to tally up their rankings on the search engine. Although Google Penguin has been presented as an algorithm aimed at case web spam, it truly focuses on spammy links by gauging the feel of the sites the contacts are coming from. The 2013 Google Hummingbird update featured an algorithm bend designed to combine Google’s natural language dealing out and semantic conformity of web pages. Hummingbird’s language doling out system falls below the newly ascribed 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 designed 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 Begin applying BERT models for English language search queries in the US. Bidirectional Encoder Representations from Transformers (BERT) was another attempt by Google to enhance their natural language processing, but this become old in order to better understand the search queries of their users. In terms of search engine optimization, BERT designed to attach users more easily to relevant content and addition the tone 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 aligned from further search engine-indexed pages attain 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 consent 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 everything pages are found, especially pages that are not discoverable by automatically in the express of links in accessory to their URL agreement console. Yahoo! formerly operated a paid agreement 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 in the same way as crawling a site. Not every page is indexed by search engines. The estrange of pages from the root reference book 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 fine-tune to the quirk crawling websites and started to make their index mobile-first, which means the mobile description of a unmovable 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 relation of Chromium (74 at the get older 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 suspend was to permit webmasters mature to update their code that responded to particular bot User-Agent strings. Google ran evaluations and felt confident the impact would be minor.

To avoid undesirable content in the search indexes, webmasters can instruct spiders not to crawl Definite files or directories through the welcome robots.txt file in the root manual 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 then 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 living thing crawled append 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 suitably ensure that pages are not indexed, a page-level robot’s meta tag should be included.

A variety of methods can addition the emphasis of a webpage within the search results. Cross linking amongst pages of the similar website to pay for more connections to important pages may supplement its visibility. Page design makes users trust a site and desire to stay later they locate it. When people bounce off a site, it counts adjacent to the site and affects its credibility.   Writing content that includes frequently searched keyword phrases for that reason as to be relevant to a wide variety of search queries will tend to accrual traffic. Updating content fittingly as to keep search engines crawling support frequently can give additional weight to a site. Adding relevant keywords to a web page’s metadata, including the title tag and meta description, will tend to insert the relevancy of a site’s search listings, thus increasing traffic. URL canonicalization of web pages accessible via complex URLs, using the canonical associate element or via 301 redirects can help make Definite links to swing versions of the URL all count towards the page’s partner popularity score. These are known as incoming links, which reduction to the URL and can attach 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 ration 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 hat SEO or black hat 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 once 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 more or less following guidelines but is very nearly ensuring that the content a search engine indexes and like ranks is the same content a addict will see. White cap advice is generally summed taking place as creating content for users, not for search engines, and subsequently making that content easily accessible to the online “spider” algorithms, rather than attempting to trick the algorithm from its intended purpose. White cap SEO is in many ways similar to web early payment that promotes accessibility, although the two are not identical.

Black cap SEO attempts to combine rankings in ways that are disapproved of by the search engines or change deception. One black hat technique uses hidden text, either as text colored same to the background, in an invisible div, or positioned off-screen. Another method gives a swap page depending on whether the page is instinctive 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 middle of the black hat and white cap approaches, where the methods employed avoid the site creature penalized but reach not proceedings in producing the best content for users. Grey hat SEO is very 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 capture strategy for all website, and additional Internet marketing strategies can be more effective, such as paid advertising through pay-per-click (PPC) campaigns, depending on the site operator’s goals. Search engine marketing (SEM) is the practice of designing, running, and optimizing search engine ad campaigns. Its difference from SEO is most suitably depicted as the difference surrounded by paid and unpaid priority ranking in search results. SEM focuses upon prominence more suitably than relevance; website developers should regard SEM next the utmost importance similar to consideration to visibility as most navigate to the primary listings of their search. A well-off Internet promotion campaign may plus depend upon building high-quality web pages to engage and convince internet users, setting happening analytics programs to enable site owners to discharge duty results, and improving a site’s conversion rate. In November 2015, Google released a full 160-page story 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 puff 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 deed up their website to the search engine results and determine how open their websites are. The closer the keywords are together their ranking will append based on key terms.

SEO may generate an agreeable 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 want of guarantee and uncertainty, a concern that relies heavily on search engine traffic can strive 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 deafening loss of traffic. According to Google’s CEO, Eric Schmidt, in 2010, Google made on peak of 500 algorithm changes – almost 1.5 per day. It is considered a wise thing practice for website operators to liberate themselves from dependence upon search engine traffic. In auxiliary to accessibility in terms of web crawlers (addressed above), user web accessibility has become increasingly important for SEO.

Optimization techniques are very tuned to the dominant search engines in the objective market.
The search engines’ market shares adjust from make public to market, as does competition.
In 2003, Danny Sullivan declared that Google represented virtually 75% of whatever searches. In markets outside the United States, Google’s portion is often larger, and Google remains the dominant search engine worldwide as of 2007. As of 2006, Google had an 85–90% market portion 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 close to 90% according to Hitwise. That broadcast share is achieved in a number of countries.

As of 2009, there are lonely a few large markets where Google is not the leading search engine. In most cases, when Google is not leading in a unmovable 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 push leaders.

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

On October 17, 2002, SearchKing filed prosecution 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 settled Google’s movement to dismiss the disease because SearchKing “failed to divulge a claim upon which utility may be granted.”

In March 2006, KinderStart filed a lawsuit next to Google more 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 alter and partially approved Google’s commotion for Rule 11 sanctions next to KinderStart’s attorney, requiring him to pay portion of Google’s valid expenses.