SSML is often embedded in VoiceXML scripts to drive interactive telephony systems.
For desktop applications, other markup languages are popular, including Apple's embedded speech commands, and Microsoft's SAPI Text to speech (TTS) markup, also an XML language.
It is also used to produce sounds via Azure Cognitive Services' Text to Speech API or when writing third-party skills for Google Assistant or Amazon Alexa.
SSML is based on the Java Speech Markup Language (JSML) developed by Sun Microsystems, although the current recommendation was developed mostly by speech synthesis vendors.
It covers virtually all aspects of synthesis, although some areas have been left unspecified, so each vendor accepts a different variant of the language.