OneDrive Folder Size Looks Different Online and Locally

When you check the size of a folder in OneDrive on your computer and then compare it to the same folder on the OneDrive website, the numbers often do not match. This difference happens because OneDrive uses Files On-Demand, which changes how folder sizes are calculated locally versus in the cloud. Local sizes can be affected by compressed files, hidden system files, and sync state markers. This article explains the technical reasons for the discrepancy and shows you how to get an accurate folder size in both locations.

Why OneDrive Folder Sizes Differ Between Online and Local Views

OneDrive uses a feature called Files On-Demand that lets you see all your files in File Explorer without downloading them to your hard drive. Files with a blue cloud icon are online-only, meaning they exist only in the cloud and consume zero bytes on your local disk. Only files with a green checkmark or a solid green circle are fully downloaded and physically stored on your computer. This design is the primary reason for the size mismatch.

When you right-click a folder in File Explorer and select Properties, Windows calculates the folder size by adding up the bytes of all files that are physically present on the drive. Online-only files are excluded from this calculation because they are not stored locally. On the OneDrive website, the folder size is the sum of all file sizes stored in the cloud, including files you have not downloaded. The website does not know which files are local and which are online-only.

Compression and Hidden Files

Windows may compress certain files on NTFS volumes to save disk space. When Windows compresses a file, the local size reported by File Explorer is the compressed size, not the original size. The OneDrive website always reports the uncompressed size. This difference can make a folder appear larger online than on your computer.

Hidden files and system files such as desktop.ini or thumbs.db are present in local folders but are not uploaded to OneDrive. These files add a small amount to the local folder size but do not appear in the online size. The opposite can also be true: OneDrive may store metadata files or version history that is not visible in File Explorer, increasing the online size.

Sync State and Pending Changes

If a file is currently syncing, its local size may be zero or partial until the download completes. Files that are marked as “Always keep on this device” are fully downloaded and count toward the local size. Files that are set to “Free up space” revert to online-only and are removed from the local size calculation. The OneDrive website always shows the full cloud size regardless of sync state.

Steps to Compare OneDrive Folder Sizes Accurately

To get a reliable comparison between local and online folder sizes, you must ensure all files in the folder are fully downloaded. Follow these steps.

1. Make all files in the folder available offline
   Open File Explorer and navigate to the OneDrive folder. Right-click the folder you want to check and select Always keep on this device. Wait for all files to download. You will see green checkmarks on every file.
2. Verify all files are synced
   Open the OneDrive icon in the system tray. If the icon shows a green checkmark, sync is complete. If it shows a spinning circle or a red X, wait for sync to finish or resolve any errors.
3. Check the local folder size in File Explorer
   Right-click the folder and select Properties. On the General tab, look at Size and Size on disk. Write down the number.
4. Check the online folder size on the OneDrive website
   Open a web browser and go to onedrive.live.com. Sign in with your Microsoft 365 account. Navigate to the same folder. Hover over the folder name and click the circle that appears to select it. Look at the details pane on the right side. The size is listed under Properties.
5. Compare the two numbers
   If all files are fully downloaded and no compression is applied, the local and online sizes should match within a small margin. A difference of a few kilobytes is normal due to hidden files or metadata.

If OneDrive Folder Sizes Still Do Not Match

The local size is significantly smaller than the online size

This usually means some files in the folder are still online-only. Go back to File Explorer and check the status icons. If you see any blue cloud icons, right-click the folder again and select Always keep on this device. Wait for the download to finish. If the size still differs, check for compressed files. Open the folder, right-click any large file, select Properties, and look at the Advanced attributes. If Compress contents to save disk space is checked, the local size will be smaller than the online size.

The local size is larger than the online size

This is rare but can happen if you have local files that are not uploaded to OneDrive. Check if the folder contains files or subfolders that are excluded from sync. Open OneDrive settings by right-clicking the OneDrive icon in the system tray and selecting Settings. Go to the Account tab and click Choose folders. Verify that all necessary subfolders are selected for sync. Files stored outside the OneDrive folder will not appear online.

The folder size on the website shows a different number every time you refresh

This behavior is normal when files are actively being edited or synced. The online size updates in real time as files are added, modified, or deleted. Wait a few minutes and refresh the page. If the size keeps changing, check the sync activity in the OneDrive system tray icon. Large file transfers or ongoing edits will cause the size to fluctuate.

Item	File Explorer Local Size	OneDrive Website Size
Description	Sum of bytes for files physically stored on the local hard drive	Sum of bytes for all files stored in the cloud, including online-only files
Includes online-only files	No	Yes
Includes compressed file size	Yes, reports compressed size if NTFS compression is enabled	No, always reports uncompressed size
Includes hidden system files	Yes, includes desktop.ini, thumbs.db, and similar files	No
Updates in real time	Updates after sync completes and File Explorer refreshes	Updates as files are modified in the cloud

To get matching sizes, make all files available offline and disable NTFS compression on the folder. Use the Always keep on this device option from the right-click menu to force a full download. After that, the local and online sizes will match within a few kilobytes.