Includes: Instagram, WhatsApp, Messenger
When it was first blocked: July 2009, in the wake of deadly riots in western China when the platform was used for communication among protesters. Instagram was blocked in September 2014 during pro-democracy protests in Hong Kong, and WhatsApp was blocked in September 2017.
Includes: YouTube, Gmail, Google Play, Google Maps, Google Drive, Hangouts, Blogger
When it was first blocked: YouTube was blocked on-and-off multiple times in the late 2000s, including in October 2007, March 2008 during riots in Tibet, and in March 2009 when it went down in the country for good.
Particular queries on Google, including those related to politics, have long been censored in China. Google.cn, the company's China-based search engine, was shut down in 2010 following disputes over censorship of search queries. Google's family of apps — including Gmail and Google Maps — have went offline multiple times, including in November 2012 and December 2014.
Reports emerged in 2018 that Google was working on a censored search engine for Chinese users called Project Dragonfly. The project was reportedly cancelled in December after facing outrage from Google employees and human rights groups, but some activists are not fully convinced Google has officially scrapped plans.
Includes: Periscope
When it was first blocked: June 2009, shortly before the 20th anniversary of the Tiananmen Square protests in 1989, when the Chinese army killed hundreds of students demanding democracy.
Despite the ban, Twitter still has an estimated 10 million active users in China, who use VPNs to circumvent the ban.
Snapchat
When it was first blocked: It's unclear when Snapchat was initially banned in China, but the social platform does have a small office in the country to work on Spectacles, Snap's camera-equipped smart sunglasses.
When it was first blocked: August 2018, although many Redditors were more surprised the site hadn't been banned earlier.
Tumblr
When it was first blocked: May 2016, although pages containing political and pornographic content have been heavily censored in China before then.
When it was first blocked: March 2017, around the time when China was hosting its annual "Two Sessions" political gathering.
Slack
When it was first blocked: The timeline of when Slack was first blocked in China is not clear, but access to the messaging app has been "somewhat inconsistent" for years, according to the company itself.
Twitch, an Amazon subsidiary
When it was first blocked: September 2018, after app downloads skyrocketed for those in China who wanted to catch e-sports matches at the 2018 Asian Games.
Discord
When it was first blocked: Reports first surfaced in mid-2018 that users of the popular chat app for gamers were unable to access the service in China.
Dropbox
When it was first blocked: May 2010. Access to Dropbox was temporarily restored in February 2014, but its website and apps were blocked again in China by that June.
Wikipedia
When it was first blocked: Wikipedia's Chinese-language edition has been blocked for good since 2015, but China barred all language versions of Wikipedia more recently: this May.
Flickr
When it was first blocked: The photo site went behind the "Great Firewall" in June 2007, just a few years after Yahoo bought it. Nowadays, SmugMug owns Flickr, but it doesn't appear like the site's situation in China has changed at all.
SoundCloud
When it was first blocked: The music-sharing service was first blocked in September 2013. Since then, it's been blocked in China intermittently, including in May 2015.
DuckDuckGo
When it was first blocked: The privacy-focused search engine was blocked in September 2014.
