Files

viewer.open(file) picks an engine from the extension. The playground has the mount for each framework.

Kind	Extensions
PDF	`.pdf`
Word	`.doc`, `.docx`, `.docm`, `.dot`, `.dotx`, `.dotm`
Excel	`.xls`, `.xlsx`, `.xlsm`, `.xlt`, `.xltx`, `.xltm`, `.xlsb`
PowerPoint	`.ppt`, `.pptx`, `.pptm`, `.pot`, `.potx`, `.pps`, `.ppsx`
Image	`.png`, `.jpg`, `.jpeg`, `.gif`, `.webp`, `.bmp`, `.tif`, `.tiff`
Vector	`.svg`, `.ai`
CSV	`.csv`
Audio	`.mp3`, `.wav`, `.m4a`
Video	`.mp4`, `.mpeg`, `.mpg`, `.webm`
Archive	`.zip`, `.gz`, `.tgz`, `.tar`, `.7z`
Mail	`.eml`, `.msg`

A format that cannot do an action reports that it is unsupported. Save writes the format that was opened.