New Outlook ICS Files Settings: Location and Practical Limits

When you import or open an ICS calendar file in the new Outlook for Windows, the application stores the calendar data in a specific location on your hard drive. Understanding where these files are saved and what limits apply to ICS file processing helps you manage your calendar imports more effectively. This article explains the default storage location for ICS files, the maximum file size and event count limits, and how these settings affect your workflow.

The new Outlook uses a different storage architecture than classic Outlook, which changes how ICS files are handled. Unlike classic Outlook that stores imported calendars in your Exchange or PST mailbox, the new Outlook saves them in a local cache folder tied to your Microsoft 365 or Outlook.com account. This shift introduces practical limits on file size, event count, and recurring event complexity that you need to consider before importing large or complex ICS files.

This article covers the exact folder path where ICS files are stored, the maximum file size and event limits imposed by the new Outlook, and what happens when you exceed those limits. You will also learn how to check your current ICS file settings and what alternatives exist for importing large calendar files.

How the New Outlook Stores ICS Calendar Files

The new Outlook for Windows is a Universal Windows Platform app that runs in a sandboxed environment. This sandboxing means all app data, including imported ICS calendar files, is stored in a dedicated app package folder rather than in the traditional Outlook PST or OST file locations. The ICS folder path is:

%LocalAppData%\Packages\Microsoft.OutlookForWindows_8wekyb3d8bbwe\LocalCache\Roaming\Outlook\ICS

To access this folder, open File Explorer and paste the path above into the address bar. Replace %LocalAppData% with your actual local app data folder, which is typically C:\Users\YourUsername\AppData\Local. The ICS subfolder may not exist until you import your first ICS file. Each imported ICS file creates a separate subfolder named with a GUID. Inside that subfolder, the calendar data is stored in a SQLite database file named CalendarData.db. The original ICS file is not retained as a standalone file after import. Instead, the new Outlook extracts the events and stores them in the local SQLite database, which is then synced to your Microsoft 365 mailbox.

Why the Storage Location Matters

The sandboxed storage location has two practical consequences. First, you cannot manually copy or move ICS files into this folder to import them. You must use the Outlook interface by selecting File > Open & Export > Import/Export or by double-clicking an ICS file. Second, if you uninstall the new Outlook or reset the app, all imported ICS calendar data is deleted. There is no mechanism to preserve imported calendars across app reinstalls. You must re-import the ICS files after a reset.

How to Verify the Current ICS Storage Path

To confirm which folder your new Outlook is using for ICS file storage, follow these steps:

1. Open Account Settings
   In the new Outlook, click File in the top-left corner. Click Account Settings and select Account Settings from the dropdown menu.
2. Switch to the Data Files tab
   In the Account Settings dialog, click the Data Files tab. You will see a list of all data files associated with your account.
3. Locate the ICS entry
   Look for an entry labeled ICS Calendar Cache or something similar. The Location column shows the full folder path. If no ICS files have been imported, this entry will not appear.

Practical Limits of ICS File Imports in the New Outlook

The new Outlook enforces three hard limits when importing ICS files. Exceeding any of these limits causes the import to fail partially or completely.

Maximum File Size: 10 MB

The new Outlook cannot import ICS files larger than 10 MB. This limit is enforced at the application level, not by your mailbox. If you attempt to import a 12 MB file, Outlook displays an error message stating the file is too large. The import stops without adding any events. To work around this limit, split the ICS file into smaller chunks using a text editor or a dedicated ICS splitting tool. Each chunk must stay under 10 MB.

Maximum Event Count: 1000 Events

Even if the file size is under 10 MB, the new Outlook limits a single ICS import to 1000 calendar events. Events beyond the 1000th are silently ignored. The application does not warn you about this limit. After the import, you will see only the first 1000 events in your calendar. To import more events, split the ICS file into multiple files, each containing up to 1000 events, and import them one at a time.

Recurring Event Complexity

The new Outlook supports standard recurring event patterns such as daily, weekly, monthly, and yearly. However, complex recurrence rules, such as events that occur on the last weekday of every month or events with multiple exception dates, may not import correctly. The application may flatten complex recurrences into individual instances, which counts against the 1000-event limit. For example, a weekly event with 200 occurrences counts as 200 events, not one. To avoid unexpected behavior, test a small sample of your ICS file with complex recurrences before importing the full file.

If the New Outlook Still Has Issues After Importing ICS Files

Imported Calendar Events Are Missing or Duplicated

If you see missing or duplicate events after importing an ICS file, the most likely cause is exceeding the 1000-event limit or having overlapping imports. Check the file size and event count before importing. To remove duplicates, go to the calendar view, select all events from the imported calendar, and delete them. Then re-import the ICS file in smaller batches of 500 events each. Use a third-party ICS viewer to count the total events in your file before importing.

ICS File Won’t Open or Import

When an ICS file fails to open or import, verify the file is not corrupted by opening it in a text editor. Look for the BEGIN:VCALENDAR and END:VCALENDAR tags. If those tags are missing or malformed, the file is invalid. Also check that the file extension is .ics and not .ics.txt or another extension. Rename the file if necessary. If the file is valid but still fails, try importing it into classic Outlook or Google Calendar to confirm the file itself works. If it works elsewhere, the issue is specific to the new Outlook sandbox limits.

Calendar Data Not Syncing After Import

After importing an ICS file, the events appear in your calendar but may not sync to your other devices. This happens because the new Outlook stores imported ICS events in the local SQLite database first and then syncs them to the server. Sync can take several minutes for large imports. To force a sync, click the Send/Receive button on the Home tab. If events still do not sync after 30 minutes, sign out of your Microsoft 365 account and sign back in. This triggers a full sync cycle.

ICS File Storage in New Outlook vs Classic Outlook

Item	New Outlook	Classic Outlook
Storage location	%LocalAppData%\Packages\Microsoft.OutlookForWindows_8wekyb3d8bbwe\LocalCache\Roaming\Outlook\ICS	%LocalAppData%\Microsoft\Outlook\ or a PST file
Maximum ICS file size	10 MB	No hard limit (limited by PST file size)
Maximum events per import	1000	No hard limit
Recurring event support	Standard recurrences only	Full recurrence support
File persistence after import	Original ICS file is deleted	Original ICS file is retained
Sync behavior	Local database syncs to server	Directly imported to mailbox

The new Outlook ICS file storage and import system has tighter limits than classic Outlook. You cannot import files larger than 10 MB or more than 1000 events at once. Complex recurring events may be flattened into individual instances. The storage location is in a sandboxed app folder that is deleted when you uninstall the app. To work with large calendar files, split them into smaller files of 1000 events or less and keep a backup copy of the original ICS file outside the new Outlook folder. Consider using classic Outlook or a third-party calendar tool for importing ICS files that exceed these limits.