File used by Windows Live Messenger (WLM), an online chat program; contains metadata such as emoticon name and keyboard shortcut; used in combination with an associated .DT2 image file to display an emoticon; can be used to create custom emoticons.

ID2 files are encrypted and decrypted using a WLM user's Passport User ID (PUID). In Windows XP, ID2 files typically are stored in the following user subdirectory: "\Application Data\Microsoft\Messenger\[LiveID]\ObjectStore\CustomEmoticons". In Windows Vista, they typically are stored in the following user subdirectory: "\AppData\Microsoft\Messenger\[LiveID]\ ObjectStore\CustomEmoticons". ID2 files often have cryptic names because they are automatically named using a hash of the .DT2 file. NOTE: Windows Live Messenger was discontinued in 2013 and has moved to Skype.