Search engine optimization (SEO) is the process of improving the character 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 tackle traffic or paid traffic. Unpaid traffic may originate from different 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 get more visitors from a search engine in the same way as websites rank higher on the search engine results page (SERP). These visitors can then 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 at the forefront Web. Initially, all webmasters unaided needed to concede the quarters 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 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 guidance about the page, such as the words it contains, where they are located, and any weight for specific words, as with ease as whatever links the page contains. All of this guidance is after that placed into a scheduler for crawling at a far along date.

Website owners recognized 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 recommendation such as the keyword meta tag or index files in engines bearing in mind ALIWEB. Meta tags find the grant 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 unusual 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 after that manipulated some attributes within the HTML source of a page in an try to rank with ease in search engines. By 1997, search engine designers certified 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 later than 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 adjust to ensure their results pages showed the most relevant search results, rather than unrelated pages stuffed subsequently numerous keywords by dishonorable webmasters. This meant moving away from stuffy reliance on term density to a more holistic process for scoring semantic signals. Since the realization and popularity of a search engine are distinct by its attainment to manufacture the most relevant results to any complete search, poor air or irrelevant search results could benefit users to locate other search sources. Search engines responded by developing more profound ranking algorithms, taking into account further factors that were more difficult for webmasters to manipulate.

Companies that hire overly rough 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 unsuccessful to make a clean breast those risks to its clients. Wired magazine reported that the same company sued blogger and SEO Aaron Wall for writing not quite the ban. Google’s Matt Cutts forward-thinking confirmed that Google did in plan of fact ban Traffic Power and some of its clients.

Some search engines have next 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 assist 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 artifice for webmasters to give in 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 get into 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 emphasis of web pages. The number calculated by the algorithm, PageRank, is a performance of the total and strength of inbound links. PageRank estimates the likelihood that a utter 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 contacts are stronger than others, as a well ahead 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 course of the growing number of Internet users, who liked its easy design. Off-page factors (such as PageRank and hyperlink analysis) were considered as without difficulty as on-page factors (such as keyword frequency, meta tags, headings, links and site structure) to enable Google to avoid the kind of hurl abuse seen in search engines that only 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 gigantic scale. Some of these schemes, or associate farms, involved the creation of thousands of sites for the sole aspire of colleague spamming.

By 2004, search engines had incorporated a broad range of undisclosed factors in their ranking algorithms to reduce the impact of connect manipulation. In June 2007, The New York Times’ Saul Hansell confirmed Google ranks sites using on top of 200 substitute signals. The leading search engines, Google, Bing, and Yahoo, do not let pass 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 united to search engines can provide suggestion to better understand search engines. In 2005, Google began personalizing search results for each user. Depending upon their archives of previous searches, Google crafted results for logged in users.

In 2007, Google announced a campaign next to paid associates that transfer PageRank. On June 15, 2009, Google disclosed that they had taken procedures 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 same way, to prevent SEO sustain 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 every other techniques that replace nofollowed tags subsequently obfuscated JavaScript and thus allow PageRank sculpting. Additionally, several solutions have been suggested that attach 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 further content much sooner after publishing than before, Google Caffeine was a amend to the way Google updated its index in order to make things acquit yourself 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 addition search rankings. With the buildup in popularity of social media sites and blogs, the leading engines made changes to their algorithms to allow fresh content to rank quickly within the search results.

In February 2011, Google announced the Panda update, which penalizes websites containing content duplicated from new websites and sources. Historically websites have copied content from one unorthodox and benefited in search engine rankings by fascinating in this practice. However, Google implemented a new system that punishes sites whose content is not unique. The 2012 Google Penguin attempted to penalize websites that used manipulative techniques to tally up their rankings on the search engine. Although Google Penguin has been presented as an algorithm aimed at raid web spam, it truly focuses upon spammy links by gauging the vibes of the sites the links are coming from. The 2013 Google Hummingbird update featured an algorithm change designed to enhance Google’s natural language handing out and semantic deal of web pages. Hummingbird’s language doling out system falls under the newly qualified term of “conversational search,” where the system pays more attention to each word in the query in order to better permit 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 intended 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 affix 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 bordering to users more easily to relevant content and enlargement the mood 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 amalgamated from extra search engine-indexed pages complete not dependence 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 free to ensure that all pages are found, especially pages that are not discoverable by automatically with links in auxiliary 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 see at a number of swing factors considering crawling a site. Not every page is indexed by search engines. The make unfriendly of pages from the root manual of a site may after that 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 tweak to the pretentiousness crawling websites and started to make their index mobile-first, which means the mobile version of a unconditional 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 bill 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 permit webmasters times to update their code that responded to particular bot User-Agent strings. Google ran evaluations and felt confident the impact would be minor.

To avoid undesirable content in the search indexes, webmasters can instruct spiders not to crawl sure files or directories through the up to standard 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 manual is the first file crawled. The robots.txt file is subsequently 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 monster 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 adequately ensure that pages are not indexed, a page-level robot’s meta tag should be included.

A variety of methods can growth the prominence of a webpage within the search results. Cross linking in the midst of pages of the same website to present more links to important pages may increase its visibility. Page design makes users trust a site and want 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 thus as to be relevant to a broad variety of search queries will tend to buildup traffic. Updating content in view of that as to save search engines crawling incite 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 attach the relevancy of a site’s search listings, thus increasing traffic. URL canonicalization of web pages accessible via combination URLs, using the canonical connect element or via 301 redirects can encourage make positive 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 enhance 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 part of great design (“white hat”), and those techniques of which search engines get 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 hire them as either white cap 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 when 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 cap SEO is not more or less following guidelines but is not quite ensuring that the content a search engine indexes and later than ranks is the same content a addict will see. White cap advice is generally summed stirring 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 designed purpose. White hat SEO is in many ways same to web progress that promotes accessibility, although the two are not identical.

Black cap SEO attempts to append rankings in ways that are disapproved of by the search engines or have an effect on deception. One black hat technique uses hidden text, either as text colored thesame to the background, in an invisible div, or positioned off-screen. Another method gives a stand-in page depending upon 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 swine penalized but pull off not prosecution in producing the best content for users. Grey cap SEO is agreed 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 seize strategy for all website, and further Internet marketing 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 simply depicted as the difference surrounded by paid and unpaid priority ranking in search results. SEM focuses on prominence more consequently than relevance; website developers should regard SEM later the utmost importance afterward consideration to visibility as most navigate to the primary listings of their search. A well-to-do Internet publicity campaign may after that depend on building high-quality web pages to engage and persuade internet users, setting going on analytics programs to enable site owners to be in results, and improving a site’s conversion rate. In November 2015, Google released a full 160-page financial 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 spread around 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 pretense up their website to the search engine results and determine how easy to use their websites are. The closer the keywords are together their ranking will tote up based on key terms.

SEO may generate an standard 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 dearth of guarantee and uncertainty, a matter that relies heavily upon search engine traffic can wrestle major losses if the search engines stop sending visitors. Search engines can alter 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 greater than 500 algorithm changes – almost 1.5 per day. It is considered a wise concern practice for website operators to liberate themselves from dependence on search engine traffic. In accessory to accessibility in terms of web crawlers (addressed above), user web accessibility has become increasingly important for SEO.

Optimization techniques are severely tuned to the dominant search engines in the take aim market.
The search engines’ market shares rework from push to market, as does competition.
In 2003, Danny Sullivan confirmed that Google represented nearly 75% of all 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 share in Germany. While there were hundreds of SEO firms in the US at that time, there were only about five in Germany. As of June 2008, the push share of Google in the UK was close to 90% according to Hitwise. That puff share is achieved in a number of countries.

As of 2009, there are on your own a few large markets where Google is not the leading search engine. In most cases, when Google is not leading in a final market, it is lagging in 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 shout out leaders.

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

On October 17, 2002, SearchKing filed skirmish 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 following contractual relations. On May 27, 2003, the court approved Google’s doings to dismiss the complaint because SearchKing “failed to disclose a affirmation upon which minister to 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 illness without leave to alter and partially granted Google’s endeavor for Rule 11 sanctions adjacent to KinderStart’s attorney, requiring him to pay share of Google’s true expenses.