STDU Viewer is computer software, a compact viewer for many computer file formats: Portable Document Format (PDF), World Wide Fund for Nature (WWF), DjVu, comic book archive (CBR or CBZ), FB2, ePUB, XML Paper Specification (XPS), Text Compression for Reader (TCR), Mobipocket (MOBI), AZW, multi-page TIFF, text file (TXT), PalmDoc (PDB), Windows Metafile (EMF), Windows Metafile (WMF), bitmap (BMP), Graphics Interchange Format (GIF), JPEG-JPG, Portable Network Graphics (PNG), Photoshop Document (PSD), PiCture eXchange (PCX-DCX).

It displays thumbnails of pages,[4][5] it can create users' bookmarks,[4][5] make color adjustments,[6] and change text settings.

STDU Viewer was appreciated for its feature to read a wide range of ebook formats and can be considered as a replacement for Adobe Acrobat’s reader.

[5][9] STDU Viewer was included in the list of top 50 freeware of 2009[10] and best software for students.

[11] The program doesn't support formats for online help Microsoft Compiled HTML Help (CHM), Microsoft Reader (LIT),[5] document (DOC), and HyperText Markup Language (HTML).