A CTD file is a document created by Cherrytree, a note-taking application. It stores document data in XML format, which may include text, tables, images, objects, and document settings. CTD files protected with a password are saved as .CTZ files.

Users typically save Cherrytree documents as .CTB or .CTX files. They may also save documents in XML to save storage space. The documents saved in XML format are saved as CTD files and password-protected CTD files are saved as CTZ files. CTD files are typically opened by Cherrytree. However, they may also be opened by XML and text editors. NOTE: Cherrytree is developed by giuspen, a portmanteau of Giuseppe Penone.