their tweet page. Until the legacy desktop front end that was discontinued in 2020, a row with miniature profile pictures of up to ten liking or retweeting users was displayed (earliest documented implementation in December 2011 overhaul), as well as a tweet reply counter next to the according button on a tweet's page. Twitter allows users to update their profile via 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 magazine essay, technology author Steven Johnson described the basic mechanics of Twitter as "remarkably simple": Twitter announced in a tweet on September 1, 2022, that the ability to edit a tweet was being tested for a few users. The company said the feature was being tested first to determine whether it could be abused. Editing would be allowed for 30 minutes, and previous versions of an edited post would be available. Eventually, all Twitter Blue subscribers would be able to use the feature. Hashtags, usernames, retweets and replies 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. In 2014, in anticipation for the FIFA World Cup, Twitter introduced hashflags, special hashtags that automatically generate a custom emoji next to them for a certain period of time, following the success of a similar campaign during the 2010 World Cup. Hashflags may be generated by Twitter themselves (such as to raise awareness for social issues) or be purchased by corporations (such as to promote products and events). To repost a message from another Twitter user and share it with one's own followers, a user can click the retweet button within the Tweet. Users can reply to other accounts' replies. Since November 2019, users can hide replies to their messages. Since May 2020, users can select who can reply to each of their tweets before sending them: anyone, accounts who follow the poster, specific accounts, and none. This ability was upgraded in July 2021 to make the feature retroactively applicable to tweets after they have been sent out. Using SMS Through SMS, users can communicate with Twitter through five gateway numbers: short codes for the United States, Canada, India, New