Most modern browsers, especially , have strict rules for filenames passed through download APIs. The error is triggered when a filename includes:

If you’re seeing the error while using Video DownloadHelper, you are likely hitting a restriction in how browsers or operating systems handle file naming. This issue typically occurs when a video title on a website includes special symbols (like colons, slashes, or non-ASCII characters) that the Video DownloadHelper extension or your browser cannot process as a valid filename. Why This Error Happens

When the "Save As" dialog box appears, delete any special characters like colons ( : ) or slashes ( / ) from the name field.