Modern Sign Language communication
It has been suggested that this article be merged into Videotelephony#Use in sign language communications. (Discuss) Proposed since December 2018.
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Sign Language communication is a system of communication using visual gestures and signs, as used by deaf people. A unique property of Sign Language is that it is not easy to put on paper due to a lack of formal acceptance,  and is impossible to be mediated over the phone or in a plain email. Because of its three-dimensional nature, it can only be transferred in the form of timed two or three dimensional snapshots, also known as a video. The video itself has to be large and fast enough to capture sign language movements sufficiently.
In the late 1990s, it became possible for deaf people to use electronic communication tools as another channel for Sign Language. Initially, there weren't many choices prior to the advent of more interfaces (e.g. APIs like "getUserMedia".). With these, however, deaf people can perform electronic sign language exchanges independently without the need for a third person in the middle, i.e. a Video relay service.
Comparison of Sign Language communication tools
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|Tool||Owner||Free?||Pure web based?[a]||Works on desktops?||Mobile support?||Uses email?||Required hardware||Installation||Limitations||Specialities||Technologies||Deaf made?||Licensing|
|Facebook Messenger||Yes||No ||Yes||Yes||No||Any mobile||App must be installed, does not require a FB account ||?||No||100% proprietary|
|FaceTime||Apple Inc||Yes||No||Yes||Yes||No||Apple hardware only (Desktop or mobile) ||App must be installed, requires Apple ID account||?||No||100% proprietary|
|Glide (software)||Glide||Yes||No||No||Yes||No||Any mobiles||App must be installed||?||No||100% proprietary|
|Google Hangouts||Yes||No||Yes||Yes||No||Any Desktop or mobiles||App must be installed, requires Google account||?||No||100% proprietary|
|Skype||Microsoft||Yes||No||Yes||Yes||No||Any Desktop or mobile||App must be installed, requires Microsoft account||?||No||100% proprietary|