WhatsApp 限时讯息功能快将推出，而 WhatsApp 亦在官方网站的 FAQ 内讲解限时讯息的使用详情。
用家启用 WhatsApp 限时讯息功能后，在个人或群组对话中发出的讯息会在七天后消失，设定不会影响先前该对话内收发过的讯息。在一般个人对话，对话双方都可以选择开启或关闭限时讯息功能，而群组通话中就只有管理员有权限开启或关闭限时讯息功能。
另外，使用限时讯息有几项要留意。若果使用超过七天后才打开 WhatsApp，讯息将会消失。但若七天后讯息预览仍有保留的话，有可能在预览中看到该讯息。
若回复限时讯息，加上引号的文字在七天后仍可能会留存于对话中。而将限时讯息转寄至限时讯息功能关闭的对话中，该转寄讯息不会在对话中消失。至于多媒体内容若果在限时讯息中传送，多媒体档案也会消失，但若果多媒体已经下载的话，档案仍是会储存在手机内。
If a user doesn’t open WhatsApp in the seven day period, the message will disappear. However, the preview of the message might still be displayed in notifications until WhatsApp is opened.
When you reply to a message, the initial message is quoted. If you reply to a disappearing message, the quoted text might remain in the chat after seven days.
If a disappearing message is forwarded to a chat with disappearing messages off, the message won’t disappear in the forwarded chat.
If a user creates a backup before a message disappears, the disappearing message will be included in the backup. Disappearing messages will be deleted when a user restores from a backup.
Source: WhatsApp FAQ