Why isn't cookie import working?
Having trouble importing cookies? Don’t worry – here are the most common issues, why they happen, and how to fix them in no time!
Issue 1: error “File cookies must be in JSON or Netscape formats. Please try again.”
This error happens because the format checker doesn’t support nested JSON values like "partitionKey":{"topLevelSite":"https://google.com"}
.
Here's how to fix it:
Remove all occurrences of the "partitionKey"
block from your JSON file like on the screenshot below, then save and try to import the file again.

Issue 2: only some cookies import successfully
When you import cookies, only some make it through – frustrating, right? It’s usually because a few don’t meet the right format, or there’s a small hiccup during the process.
Here's how to fix it:
- Find the missing cookies: see which ones didn’t make it through
Check cookies
Here's how you can view cookies in a browser:
- For Mimic, paste
chrome://settings/content/all
into the browser address bar - For Stealthfox, paste
about:preferences#privacy
into the browser address bar, and on the page that opens, select “Cookies” → “Manage data”
- Retry importing: only re-import the missing cookies to save time
Issue 3: cookie import freezes or fails
If the process freezes, or you see a “Failed to import cookies” error, don’t panic! This might happen if your Windows username has non-Latin characters (like Cyrillic) or if the cookie file format isn’t supported.
Here's how to fix it:
- Try manual paste: copy the cookies as plain text and paste them directly into the cookie import window
- Check your username (Windows only): make sure it only uses Latin characters (for example, no special characters or Cyrillic)
If your Windows username contains non-Latin characters or spaces, rename the current user account or create a new one. Use the guide Check your Windows username.
Nothing helps?
Still can't import cookies? Our support team will be able to pinpoint the cause of the issue once they review your log file.
Logs
- Recreate the issue or wait until the error message appears
- Archive the logs folder found in these locations:
- Windows:
C:\Users\%username%\mlx
- macOS:
/Users/%username%/mlx
- Linux:
/home/%username%/mlx
- Windows:
- Email support at [email protected] with:
- A clear description of the issue
- The archived logs folder attached