.xls

<input type="file" accept="application/vnd.ms-excel" />

.xlsx

<input type="file" accept="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet" />

.ppt

<input type="file" accept="application/vnd.ms-powerpoint" />

.pptx

<input type="file" accept="application/vnd.openxmlformats-officedocument.presentationml.presentation" />

.doc

<input type="file" accept="application/msword" />

.docx

<input type="file" accept="application/vnd.openxmlformats-officedocument.wordprocessingml.document" />

.pdf

<input type="file" accept="application/pdf" />

.csv

<input type="file" accept=".csv" />

.png/.jpg/.jpeg/.etc

<input type="file" accept="image/*" />

.txt

<input type="file" accept="text/plain" />

.htm/.html

<input type="file" accept="text/html" />

.avi/.mpg/.mpeg/.mp4

<input type="file" accept="video/*" />

.mp3/.wav/.etc

<input type="file" accept="audio/*" />

.zip

<input type="file" accept="application/x-zip-compressed" />