11 classes are annotated with LanguageNegotiation

LanguageNegotiationBrowser in core/modules/language/src/Plugin/LanguageNegotiation/LanguageNegotiationBrowser.php
Class for identifying language from the browser Accept-language HTTP header.
LanguageNegotiationContentEntity in core/modules/language/src/Plugin/LanguageNegotiation/LanguageNegotiationContentEntity.php
Class for identifying the content translation language.
LanguageNegotiationSelected in core/modules/language/src/Plugin/LanguageNegotiation/LanguageNegotiationSelected.php
Class for identifying language from a selected language.
LanguageNegotiationSession in core/modules/language/src/Plugin/LanguageNegotiation/LanguageNegotiationSession.php
Identify language from a request/session parameter.
LanguageNegotiationTest in core/modules/language/tests/language_test/src/Plugin/LanguageNegotiation/LanguageNegotiationTest.php
Class for identifying language from a selected language.
LanguageNegotiationTestTs in core/modules/language/tests/language_test/src/Plugin/LanguageNegotiation/LanguageNegotiationTestTs.php
Class for identifying language from a selected language.
LanguageNegotiationUI in core/modules/language/src/Plugin/LanguageNegotiation/LanguageNegotiationUI.php
Identifies the language from the interface text language selected for page.
LanguageNegotiationUrl in core/modules/language/src/Plugin/LanguageNegotiation/LanguageNegotiationUrl.php
Class for identifying language via URL prefix or domain.
LanguageNegotiationUrlFallback in core/modules/language/src/Plugin/LanguageNegotiation/LanguageNegotiationUrlFallback.php
Determines the language to be assigned to URLs when none is detected.
LanguageNegotiationUser in core/modules/user/src/Plugin/LanguageNegotiation/LanguageNegotiationUser.php
Class for identifying language from the user preferences.
LanguageNegotiationUserAdmin in core/modules/user/src/Plugin/LanguageNegotiation/LanguageNegotiationUserAdmin.php
Identifies admin language from the user preferences.

Buggy or inaccurate documentation? Please file an issue. Need support? Need help programming? Connect with the Drupal community.