While often used interchangeably, many of the major spreadsheet applications (Microsoft Excel, Google Sheets, OpenOffice Calc) are capable of opening both file types, but there are some differences.
Comma Separated Value (CSV)
A CSV (also called a flat file) is made up of plain text with a series of values. Commas are the “delimiter” between those values, and a “linefeed” separates each row.
Many different programs can read CSV files.
Microsoft Excel (xlsx)
An Excel Spreadsheet is a binary file that holds a great deal more types of information such as charts, images, conditional formatting than a standard CSV.
Excel Spreadsheets can only be opened by programs specifically designed to accept this file format.
Why NeverBounce Recommends Using CSV files
CSV is the standard accepted format for nearly every data upload interface on the web including CRM’s, Mail Contacts, to do lists, etc.