SheetJS Data Preview Live Demo
(Base64 text works back to IE6; drag and drop works back to IE10)

Source Code Repo
Issues?  Something look weird?  Click here and report an issue
Output Format: 
 CSV
 JSON
 FORMULAE
 HTML
 XLSX




... or paste a base64-encoding here


Advanced Demo Options:
Use Web Workers: (when available) 
Use readAsBinaryString: (when available)