You can use labels to tag, organize, and categorize messages and threads in Gmail. A label has a many-to-many relationship with messages and threads: you can apply multiple labels to a single message or thread and apply a single label to multiple messages or threads.
To manage labels, you must use the
https://www.googleapis.com/auth/gmail.labels scope. For more information
about scopes, see
Gmail API-specific authorization and authentication information.
Types of labels
Labels come in two varieties: reserved
SYSTEM labels and custom
System labels typically correspond to pre-defined elements in the Gmail web
interface such as the inbox. Systems label names are reserved; no
USER label can
be created with the same name as any
SYSTEM label. The following table lists
several of the most common Gmail system labels:
|Can be manually applied
|Applied automatically to messages that are sent with
and the user's email in the
From header, or sent by the user through
the web interface.
|Automatically applied to all
draft messages created with the
Gmail API or Gmail interface.
|Corresponds to messages that are displayed in the Personal tab of the Gmail interface.
|Corresponds to messages that are displayed in the Social tab of the Gmail interface.
|Corresponds to messages that are displayed in the Promotions tab of the Gmail interface.
|Corresponds to messages that are displayed in the Updates tab of the Gmail interface.
|Corresponds to messages that are displayed in the Forums tab of the Gmail interface.
Manage labels on messages & threads
Labels only exist on messages. For instance, if you list labels on a thread, you get a list of labels that exist on any of the messages within the thread. A label might not exist on every message within a thread. You can apply multiple labels to messages, but you can't apply labels to draft messages.
Add or remove labels to threads
When you add or remove a label to a thread, you add or remove the specified label on all existing messages in the thread.
If messages are added to a thread after you add a label, the new messages don't inherit the existing label associated with the thread. To add the label to those messages, add the label to the thread again.
To add or remove the labels associated with a thread, use
Add or remove labels to messages
When you add a label to a message, the label is added to that message and becomes associated with the thread to which the message belongs. The label isn't added to other messages within the thread.
If you remove a label from a message and it was the only message in the thread with that label, the label is also removed from the thread.
To add or remove the labels applied to a message, use