Our web interface does its best, but it does work within certain limitations. The most common "violations" of these limits involve the following:
The workbook must be saved in .xlsx format.
The workbook must have less than approximately 50,000 "filled" cells. Occasionally, data may be entered in a cell well outside the range of what a user expects, and every cell between the first cell (A1) and that "far away" cell will attempt to load, causing the browser to fail the upload.
The workbook can not contain any external workbook references.
Please note that not all Excel formulas (especially "custom functions) will not work within the web interface but many of the most common ones will such as SUM, SUMPRODUCT and IF.
You can find more information on the web interface here:
We do suggest using Chrome as your web browser when using the web interface, but it is not a requirement.
If you are experiencing issues with your workbook (I.E. formulas showing instead of values or "out of memory" error in the web browser) and you're not sure why, please contact us at firstname.lastname@example.org and include a copy of the workbook you're trying to upload.