In OneNote for the web, you can mark selected notes with tags that let you visually identify and quickly return to important items that need to follow up on, remind yourself about, or share with others. You can tag anything from a single line of text to an entire paragraph of notes.
Apply a tag
Place the cursor at the beginning of the line of text you want to tag.
On the Home tab, click Tag.
In the list of tags that appears, click the tag you want to apply. For example, to tag a follow-up question in your notes, click the question mark symbol in the list.
Note: Some tags can be applied side-by-side with other tags. If you want to replace an existing tag, first delete it and then apply the new tag you want.
Remove a tag
Place the cursor at the beginning of the line of text containing the tag.
On the Home tab, click Tag > Remove Tag
Removing tags is not only useful for when you change your mind about tags you've applied, but it also removes such items from follow-up. In the OneNote for Windows desktop app, you can create automatic To-Do lists by searching for tagged notes. To learn how to do this, see Search for tagged notes.