You can store up to 30 million items or files in a SharePoint list or library. Filtered views of large lists have a similar experience to other lists. When a list view shows more than 5000 items, you may run into a list view threshold error.
To update your list when you do, perform one or all of the following three steps.
Views showing many items work best in the modern experience. To avoid errors you might see in the classic experience, use the modern experience.
When you filter or sort by a column that doesn't have an index, an error dialog could appear. To correct, add an index manually from List Settings in the settings menu, then Indexed Columns.
Indexes are created automatically in the following two situations:
When saved views have columns used for sorting or filtering.
When sorting in the modern experience.
Note: Automatic index creation when sorting in the modern experience is limited to lists and libraries with less than 20,000 items.
Edit the list view
If an error occurs when working with a large list, edit your list view.
The following four changes remove list view threshold errors. Make all four changes to remove all the errors.
Remove sorting for the list view
from both First sort by the column and Then sort by the column, select None.
Note: Columns with column types like people, lookup, or managed metadata can cause list view threshold errors when sorting. However, you can use text, number, date, and other column types in the first sort.
Remove grouping in edit view
From both First group by the column and Then group by the column, select None.
Other edits for the list view
For all columns in the Totals section, select None.
From the Columns section, clear all but one column for display.
Note: Displaying 12 or more columns of the following types can cause a list view threshold error: people, lookup, and managed metadata. Displaying columns of other types will not.