Can I move photos I already posted into a Series?

Yes. You can group photos you've already posted into a Series without uploading them again, and you can pick more than one.

To start a new Series from posted photos:

1. Open one of the photos and select the pencil icon to edit it.
2. Open the Select Series dropdown and choose Create New Series. On desktop web it's in the sidebar. On mobile and in the app it's below the photo.
3. In the Series composer, choose Add, select the other photos you've already posted, and confirm.
4. Add a title and publish.

To add posted photos to a Series you already have, go to the Series detail page, select the pencil icon, choose Add, select your photos, confirm, and save.

A photo can only be in one Series at a time. If a photo is greyed out when you pick, it's already in another Series, so remove it from that one first.

A Series needs a title and at least two photos. Your photos stay on your profile in chronological order, and you can remove one from a Series at any time without deleting it. See Can I remove or reorder photos in a Series? and How do I add more photos to an existing Series?.