.DB File Format

Introduction

Thumbs.db is the hidden file in which Windows Explorer kept the thumbnails of a folder’s pictures, in Windows Me, Windows 2000 and Windows XP. It sits beside the pictures, and is not updated when they are moved or deleted, so it can still hold thumbnails of pictures that have gone.

Microsoft has not published the format. It is a Microsoft Compound File, the container of older Office documents, which is documented; the streams inside are known only from reverse engineering, chiefly Vinetto, and from what 327 real Thumbs.db files show. Windows Vista and later normally keep their thumbnails in per-user thumbcache_*.db files. Those are a different format and are not described here.

A Thumbs.db dropped on any page opens in the explorer, which shows the thumbnails, each with its file name and modified date from the catalogue. The oldest kind of thumbnail, whose JPEG tables are left out, is listed but not drawn.

Structure

The file is a Compound File holding one stream for each thumbnail. In the usual form there is also a stream called Catalog, which lists the pictures: the Catalog page describes it. Each thumbnail stream has a small header, then a JPEG or PNG image. A second form has no Catalog, and each stream is named by a size and a hexadecimal hash.

Also used for

• SQLite 2 database – SQLite 2.6 to 2.8’s file: 1,024-byte pages in the machine’s byte order, every value text.
• SQLite 3 database – A whole SQL database in one file: pages of b-trees, typed values, UTF-8 or UTF-16 text.

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