Excel 365 Online significantly slow than Excel 365 on Desktop

I have uploaded the sheet here: 

https://we.tl/t-PLN6kCd7TB

Thank you.

At first I have to say that your question is not related to Excel Online, because that means the free available Excel. When I try to open your file in Excel Online, it would not even open:

Therefore I've modified your first post and subject, changed "Excel Online" to "Excel 365 Online" and moved it into an other forum, which IMHO describes your concern better.

(I don't blame you, since the introduction of the 365 versions it is very difficult to know which version you actually have, most users no longer understand that. Here in the forum it doesn't get any easier either, even I don't know exactly which is the best category for your question. It's all a mess.)

Unfortunately, I can't really say anything about your file either, I currently don't have a 365 version to examine your file.

But I can speculate what might be the reason: The desktop versions of Excel use several processor cores, check out this option in your version:

I would just try and deactivate the multi-core calculation and see what happens.

You use SORT FILTER UNIQUE, from the developers view I know that this routines need much more resources as usual functions.

For testing purposes I would remove all formulas from the database and replace them with values. So you might find the bottleneck.

I'm sorry, I can't help you any further. If no one else jumps into this thread I suggest that you contact the Microsoft support directly.

Global Customer Service phone numbers

All the best, stay healthy.

Andreas.

At first check this article and determine your file if you can optimize it

https://docs.microsoft.com/en-us/office/vba/excel/concepts/excel-performance/excel-tips-for-optimizing-performance-obstructions

If you need further help, we need to see your file.

Make a copy of your original file and anonymize the necessary data. For this please download this file

https://www.dropbox.com/s/rkfxuh85j5wyj9y/modAnonymize.bas?dl=1

Open your Excel file

Right-click on the sheet tab

Choose "View Code"

Press CTRL-M

Select the downloaded file and import

Close the VBA editor

Select the cells with the confidential data

Press Alt-F8

Choose the macro Anonymize

Click Run

Upload it on OneDrive (or an other Online File Hoster of your choice) and post the download link here.

https://support.office.com/en-us/article/Share-OneDrive-files-and-folders-9fcc2f7d-de0c-4cec-93b0-a82024800c07

Then we can look at the file and try to find a solution. Thank you for your understanding.

Andreas.

I've started looking through the article you shared and think I am adhering to a lot of the points there - but haven't been through everything in detail. 

I have uploaded the sheet here: 

https://we.tl/t-PLN6kCd7TB

My first point of concern is that when using Excel Online no matter which cell you enter information on it indicates that some calculation is going on. As I mentioned I have been careful not to use volatile formulas to avoid that. I think there may be one in the entire workbook at 'Resource Requests!$M$1' (=TODAY()-WEEKDAY(TODAY(),3)). 

The data tab has a huge amount of data (around 64k lines). There are a number of dynamic named ranges working across that data to pull it apart and use it in various ways. All of the dynamic ranges are INDEX() based so again not volatile. 

The sheet is very responsive on the Desktop application, but just want to know if there are any further steps to consider for online or encourage everyone to work in the desktop application. The sheet isn't too slow - given the amount of data in place etc, but even a small pause can often be too much for a user!