Microsoft yesterday announced the latest significant performance improvements in Excel for the web. Opening workbooks, navigating within a workbook, and other interactions have received performance improvements with this update. You can find the details below.

• Loading – We’ve significantly reduced the time it takes to load a workbook, making it faster for you to start working in Excel for the web.
• Scrolling – Scrolling is a fundamental part of working in Excel. Now, even in incredibly complex sheets, scrolling is smooth and fast.
• Selection – Even more fundamental than scrolling, is the need to interact with content in your workbook. We have optimized the speed of cell selection, so you’ll experience less lag and a more fluid experience when working in the grid.
• Navigating – We optimized several navigation actions: find/search, Go-To, page-up and page-down are all now faster.
• Modifying – We developed faster cell editing and formatting experiences.

Source: Microsoft