History Hoarder replaces Chrome's new tab page with one searchable view of your browsing history and bookmarks. It requests two permissions, history and bookmarks, and nothing else: no access to the pages you visit, no content scripts and no background process.
When you open a new tab it reads a bounded part of your Chrome history and your bookmark tree, in memory, to show and search them. It keeps no database of its own and stores nothing. It adds or removes a bookmark only when you click to save or remove a page.
History Hoarder sends no data to its developer or anyone else: it makes no network requests and has no account, analytics or advertising. Your history and bookmarks stay where Chrome keeps them.
Removing the extension restores Chrome's own new tab page; your history and bookmarks are untouched, because they belong to Chrome. This statement describes version 0.1.0.