Twitter is an online social networking service and microblogging service that enables its users to send and read text-based messages of up to 140 characters, known as tweets.

Twitter was created in March 2006 by Jack Dorsey and by July, the social networking site was launched. The service rapidly gained worldwide popularity, with over 500 million registered users as of 2012, generating over 340 million tweets daily and handling over 1.6 billion search queries per day. Since its launch, Twitter has become one of the ten most visited websites on the Internet, and has been described as the SMS of the Internet. Unregistered users can read tweets, while registered users can post tweets through the website interface, SMS, or a range of apps for mobile devices.

Twitter Inc. is based in San Francisco, with additional servers and offices in New York City, Boston, and San Antonio.

Twitter's origins lie in a daylong brainstorming session held by board members of the podcasting company Odeo. Dorsey, then an undergraduate student at New York University, introduced the idea of an individual using an SMS service to communicate with a small group. The original project code name for the service was twttr, an idea that Williams later ascribed to Noah Glass, inspired by Flickr and the five-character length of American SMS short codes. The developers initially considered 10958 as a short code, but later changed it to 40404 for ease of use and memorability. Work on the project started on March 21, 2006, when Dorsey published the first Twitter message at 950 PM Pacific Standard Time (PST) just setting up my twttr。

...we came across the word 'twitter', and it was just perfect. The definition was 'a short burst of inconsequential information,' and 'chirps from birds'. And that's exactly what the product was. – Jack

The first Twitter prototype was used as an internal service for Odeo employees and the full version was introduced publicly on July 15, 2006. In October 2006, Biz Stone, Evan Williams, Dorsey, and other members of Odeo formed Obvious Corporation and acquired Odeo and all of its assets – including Odeo.com and Twitter.com – from the investors and shareholders.Williams fired Glass, who was silent about his part in Twitter's startup until 2011.Twitter spun off into its own company in April 2007.

The tipping point for Twitter's popularity was the 2007 South by Southwest Interactive (SXSWi) conference. During the event, Twitter usage increased from 20,000 tweets per day to 60,000.The Twitter people cleverly placed two 60-inch plasma screens in the conference hallways, exclusively streaming Twitter messages, remarked Newsweek's Steven Levy. Hundreds of conference-goers kept tabs on each other via constant twitters. Panelists and speakers mentioned the service, and the bloggers in attendance touted it.

Reaction at the conference was highly positive. Blogger Scott Beale said that Twitter absolutely rul[SXSWi. Social software researcher danah boyd said Twitter own[ed] the conference. Twitter staff received the festival's Web Award prize with the remark we'd like to thank you in 140 characters or less. And we just did!

The first unassisted off-Earth Twitter message was posted from the International Space Station by NASA astronaut T. J. Creamer on January 22, 2010. By late November 2010, an average of a dozen updates per day were posted on the astronauts' communal account, @NASA_Astronauts. NASA has also hosted over 25 tweetups, events that provide guests with VIP access to NASA facilities and speakers with the goal of leveraging participants' social networks to further the outreach goals of NASA.

In August 2010, the company appointed Adam Bain from News Corp.'s Fox Audience Network as president of revenue.

On September 14, 2010, Twitter launched a redesigned site including a new logo.[citation needed]

Growth
The company experienced rapid growth. It had 400,000 tweets posted per quarter in 2007. This grew to 100 million tweets posted per quarter in 2008. In February 2010, Twitter users were sending 50 million tweets per day. By March 2010, the company recorded over 70,000 registered applications.As of June 2010, about 65 million tweets were posted each day, equaling about 750 tweets sent each second, according to Twitter. As of March 2011, that was about 140 million tweets posted daily.As noted on Compete.com, Twitter moved up to the third-highest-ranking social networking site in January 2009 from its previous rank of twenty-second.

Jack Dorsey, a co-founder and the chairman of Twitter, in 2009  Twitter's usage spikes during prominent events. For example, a record was set during the 2010 FIFA World Cup when fans wrote 2,940 tweets per second in the thirty-second period after Japan scored against Cameroon on June 14, 2010. The record was broken again when 3,085 tweets per second were posted after the Los Angeles Lakers' victory in the 2010 NBA Finals on June 17, 2010, and then again at the close of Japan's victory over Denmark in the World Cup when users published 3,283 tweets per second. The record was set again during the 2011 FIFA Women's World Cup Final between Japan and the United States, when 7,196 tweets per second were published. When American singer Michael Jackson died on June 25, 2009, Twitter servers crashed after users were updating their status to include the words Michael Jackson at a rate of 100,000 tweets per hour. The current record as of January 1, 2013, was set by all citizens of the Japan Standard Time Zone as the new year began, reaching a record of 33,388 tweets per second (and hence beating the previous record of 25,088, also set by Japan after a television screening of the movie Castle In The Sky).

Twitter acquired application developer Atebits on April 11, 2010. Atebits had developed the Apple Design Award-winning Twitter client Tweetie for the Mac and iPhone. The application, now called Twitter and distributed free of charge, is the official Twitter client for the iPhone, iPad and Mac.

From September through October 2010, the company began rolling out New Twitter, an entirely revamped edition of twitter.com. Changes included the ability to see pictures and videos without leaving Twitter itself by clicking on individual tweets which contain links to images and clips from a variety of supported websites including YouTube and Flickr, and a complete overhaul of the interface, which shifted links such as '@mentions' and 'Retweets' above the Twitter stream, while 'Messages' and 'Log Out' became accessible via a black bar at the very top of twitter.com. As of November 1, 2010, the company confirmed that the New Twitter experience had been rolled out to all users.

On April 5, 2011, Twitter tested a new homepage and phased out the Old Twitter. However, a glitch came about after the page was launched, so the previous retro homepage was still in use until the issues were resolved; the new homepage was reintroduced on April 20.

On December 8, 2011, Twitter overhauled its website once more to feature the Fly design, which the service says is easier for new users to follow and promotes advertising. In addition to the Home tab, the Connect and Discover tabs were introduced along with a redesigned profile and timeline of Tweets. The site's layout has been compared to that of Facebook.

On February 21, 2012, it was announced that Twitter and Yandex agreed to a partnership. Yandex, a Russian search engine, finds value within the partnership due to Twitter’s real time news feeds. Twitter’s director of business development explained that it is important to have Twitter content where Twitter
As chief executive officer, Dorsey saw the startup through two rounds of capital funding by the venture capitalists who backed the company.

On October 16, 2008, Williams took over the role of CEO, and Dorsey became chairman of the board.

On October 4, 2010, Williams announced that he was stepping down as CEO. Dick Costolo, formerly Twitter's chief operating officer, became CEO. According to a Twitter blog, dated October 4, 2010, Williams was to stay[dated info] with the company and be completely focused on product strategy.

According to The New York Times, Mr. Dorsey and Mr. Costolo forged a close relationship when Williams was away. According to PC Magazine, Williams was no longer involved in the day-to-day goings on at the company. He is focused on developing a new startup, but he became a member of Twitter's board of directors, and promised to help in any way I can. Stone is still with Twitter but is working with AOL as an advisor on volunteer efforts and philanthropy.
Dorsey rejoined Twitter in March 2011, as executive chairman focusing on product development. His time is split with Square (where he is CEO), whose offices are within walking distance of Twitter's in San Francisco.

In September 2011, board members and investors Fred Wilson and Bijan Sabet resigned from Twitter's Board of Directors.

In October 2012, Twitter announced it had hired Google executive Matt Derella to become their new director of business agency development.

Twitter has become internationally identifiable by its signature bird logo. The original logo was in use from its launch in March 2006 until September 2010. A slightly modified version succeeded the first style when the website underwent its first redesign.

On February 27, 2012, a tweet from an employee that works on the company's platform and API discussed the evolution of the Larry the Bird logo with Twitter's creative director and it was revealed that it was named after Larry Bird of the NBA's Boston Celtics fame. This detail had previously been confirmed when the Boston Celtics' director of interactive media asked Twitter co-founder Biz Stone about it in August 2011.

On June 5, 2012, Twitter unveiled its third logo redesign, replacing Larry the Bird with an updated icon simply named as the Twitter Bird. As of this logo revision, the word Twitter and the lowercase letter t are no longer used, with the bird becoming the sole symbol for the company's branding. According to Douglas Bowman, designer of Twitter, the new logo resembles a Mountain Bluebird.

The Twitter account page for Wikipedia, demonstrating the account-customized timeline view showing tweets in reverse chronological order。

Tweets are publicly visible by default, but senders can restrict message delivery to just their followers. Users can tweet via the Twitter website, compatible external applications (such as for smartphones), or by Short Message Service (SMS) available in certain countries. While the service is free, accessing it through SMS may incur phone service provider fees Users may subscribe to other users' tweets – this is known as following and subscribers are known as followers or tweeps, a portmanteau of Twitter and peeps. The users can also check the people who are un-subscribing them on Twitter (unfollowing) via various services. In addition, users have the capability to block those who have followed them.

Twitter allows users to update their profile their mobile phone either by text messaging or by apps released for certain smartphones and tablets.

Twitter has been compared to a web-based Internet Relay Chat (IRC) client. In a 2009 Time essay, technology author Steven Johnson described the basic mechanics of Twitter as remarkably simple。

As a social network, Twitter revolves around the principle of followers. When you choose to follow another Twitter user, that user's tweets appear in reverse chronological order on your main Twitter page. If you follow 20 people, you'll see a mix of tweets scrolling down the page breakfast-cereal updates, interesting new links, music recommendations, even musings on the future of education.

Content
Social networking researcher Danah Boyd responded to the Pear Analytics survey by arguing that what the Pear researchers labelled pointless babble is better characterized as social grooming andor peripheral awareness (which she explains as persons want[ing] to know what the people around them are thinking and doing and feeling, even when co-presence isn’t viable).

Format
Users can group posts together by topic or type by use of hashtags – words or phrases prefixed with a #sign. Similarly, the @ sign followed by a username is used for mentioning or replying to other users. To repost a message from another Twitter user, and share it with one's own followers, the retweet function is symbolized by RT in the message.

In late 2009, the Twitter Lists feature was added, making it possible for users to follow (as well as mention and reply to) ad hoc lists of authors instead of individual authors.

Through SMS, users can communicate with Twitter through five gateway numbers short codes for the United States, Canada, India, New Zealand, and an Isle of Man-based number for international use. There is also a short code in the United Kingdom which is only accessible to those on the Vodafone, O2and Orange
networks. In India, since Twitter only supports tweets from Bharti Airtel,an alternative platform called smsTweet was set up by a user to work on all networks. A similar platform called GladlyCast exists for mobile phone users in Singapore, Malaysia and the Philippines.

The tweets were set to a 140-character limit for compatibility with SMS messaging, introducing the shorthand notation and slang commonly used in SMS messages. The 140-character limit has also increased the usage of URL shortening services such as bit.ly, goo.gl, and tr.im, and content-hosting services, such as Twitpic, memozu.com and NotePub to accommodate multimedia content and text longer than 140 characters. Since June 2011, Twitter has used its own t.co domain for automatic shortening of all URLs posted on its website.

Trending topics
A word, phrase or topic that is tagged at a greater rate than other tags is said to be a trending topic. Trending topics become popular either through a concerted effort by users, or because of an event that prompts people to talk about one specific topic. These topics help Twitter and their users to understand what is happening in the world.

Trending topics are sometimes the result of concerted efforts by fans of certain celebrities or cultural phenomena, particularly musicians like Lady Gaga (known as Monsters), Justin Bieber (Beliebers), and One Direction (Directioners), and fans of the Twilight (Twihards) and Harry Potter (Potterheads) novels. Twitter has altered the trend algorithm in the past to prevent manipulation of this type.

Twitter's March 30, 2010 blog post announced that the hottest Twitter trending topics would scroll across the Twitter homepage.

There have been controversies surrounding Twitter trending topics Twitter has censored hashtags that other users found offensive. Twitter censored the #Thatsafrican and the thingsdarkiessayhashtags after users complained that they found the hashtags offensive.

Adding and following content
There are numerous tools for adding content, monitoring content and conversations including Telly (video sharing, old name is Twitvid),]TweetDeck, Salesforce.com, HootSuite, and Twitterfeed. As of 2009, fewer than half of tweets were posted using the web user interface with most users using third-party applications (based on analysis of 500 million tweets by Sysomos).

Verified accounts
In June 2008, Twitter launched a verification program, allowing celebrities to get their accounts verified. Originally intended to help users verify which celebrity accounts were created by the celebrities themselves (and therefore are not fake), they have since been used to verify accounts of businesses and accounts for public figures who may not actually tweet but still wish to maintain control over the account that bears their name.

Mobile
The mobile version of Twitter, mobile.twitter.com
Twitter has mobile apps for iPhone, iPad, Android, Windows Phone, BlackBerry, and Nokia S40. There is also version of the website for mobile devices, SMS and MMS service. Twitter limits the use of 3rd party applications utilizing the service by implementing a 100,000 user limit.

Authentication
As of August 31, 2010, third-party Twitter applications are required to use OAuth, an authentication method that does not require users to enter their password into the authenticating application. Previously, the OAuth authentication method was optional, it is now compulsory and the user-namepassword authentication method has been made redundant and is no longer functional. Twitter stated that the move to OAuth will mean increased security and a better experience.