SAN FRANCISCO, June 6  Google plans to make available on Tuesday morning a test version of a Web-based spreadsheet program that is intended to make it simple to edit and share lists and numeric information online.

The company said that the free program, called Google Spreadsheets, was still in the experimental stage, and that while it can read and create files in the format used by Microsoft's Excel spreadsheet program, it is not compatible with many of that program's more powerful features.

At the same time, the Web search company appears to be moving ahead in its steady march toward creating its own computing universe that is an alternative to the desktop PC software business now dominated by Microsoft.

Google executives said today that the program would make it possible for Internet users to upload two common spreadsheet and data formats, Excel and C.S.V. Once the data is on Google's Web servers, it will be possible for two or more people to simultaneously edit spreadsheet documents and chat about them using Google's instant messaging program.