Comparison of spreadsheet software

Online versus Desktop
Web-based spreadsheets do not in general depend on a particular operating system or similar constraints and are therefore generally more portable by their nature than desktop applications.
Collaborative spreadsheets
Generally, online spreadsheets offer spreadsheet sharing and public sharing as part of their features which enables collaboration between multiple users.
Remote data update
Some on-line spreadsheets provide remote data update allowing data values to be extracted from other users' spreadsheets even though they may be inactive at the time.
Gnumeric (listed below as a desktop spreadsheet) is also used as the "back-end" processor in at least one on-line spreadsheet application (Editgrid).
Online spreadsheets
The following tables only provide a comparison of desktop spreadsheet applications.
For a list and links to comparisons of online...