Yeah, that error is maddening — you're grabbing a big file, and it just dies at 80% with STG_E_INCOMPLETE. Let's cut to it.
The Quick Fix (Works 9 Times Out of 10)
- Clear your browser's cache and cookies. In Chrome or Edge, press
Ctrl+Shift+Delete, select "All time" for time range, check "Cached images and files" and "Cookies and other site data", then hit Clear data. In Firefox,Ctrl+Shift+Deleteworks too, but pick "Everything" in the time dropdown. - Restart the browser completely. Not just close the window — go to the system tray, right-click the browser icon, and quit. Or type
chrome://restartin the address bar (works for Edge too). - Download the file again. Use the same link. Don't open multiple tabs or run heavy downloads simultaneously.
If step 3 fails again, temporarily disable your antivirus real-time protection — but only for a minute. Windows Defender: Settings > Privacy & Security > Windows Security > Virus & threat protection > Manage settings > toggle Real-time protection off. Then retry the download, and turn it right back on.
Why This Works
STG_E_INCOMPLETE comes from the Structured Storage COM interface — it's the part of Windows that handles file metadata and streams. When a browser downloads a file, it writes to a temporary storage stream. If that stream gets corrupt or the browser loses its handle, the download aborts with this exact code.
Here's the kicker: the most common cause is a bloated browser cache, not the server or your connection. The browser keeps a partial file in memory, and when it tries to resume or finalize, the storage stream doesn't match what it expects. Clearing the cache resets those streams. What's actually happening is the COM layer can't complete the transaction because the cached state is corrupted.
Antivirus can trigger it too. Real-time scanning hooks into file writes, and if it holds the file open too long or flags a false positive mid-write, the stream gets truncated. That's why disabling it for 30 seconds fixes it — you're removing the interference.
Less Common Variations
Disk Space или File System Errors
If clearing cache doesn't help, check your drive. The error can also appear when the target folder is on a filesystem that doesn't support large files — like FAT32 with files over 4GB. Right-click the drive and look at properties; if it says FAT32, you need to convert to NTFS or download to a different drive.
Also run chkdsk /f on the drive. Corrupted file system metadata can break the storage stream. Open an admin command prompt and type chkdsk C: /f (replace C with your drive), then restart when asked.
VPN or Proxy Interference
VPNs and proxies add an extra layer that can corrupt the stream. Disconnect from VPN, or set the browser to "no proxy" mode. Chrome: Settings > System > Open your computer's proxy settings, then turn off any manual proxy.
Browser Extensions
Some download managers or ad-blockers interfere with how the browser writes files. Try Incognito mode — if the download works there, an extension is the culprit. Disable extensions one by one until it stops failing.
Prevention
- Clear your cache weekly if you download frequently. Use a tool like CCleaner or just the browser's built-in clearing.
- Don't pause and resume downloads repeatedly. Each resume creates a new storage stream, and that's when corruption sneaks in.
- Keep your browser updated. Old versions have known bugs with COM storage. Chrome, Edge, and Firefox all push fixes for this regularly.
- If you download huge files often, get a dedicated download manager like Internet Download Manager (IDM). It uses its own storage and doesn't touch the browser's COM streams, so this error basically disappears.
That's the whole deal. Start with the cache clear — it's boring but effective. If it still fails, antivirus is next. The rest is edge cases. You'll be back to downloading in five minutes.