Do these MP3 files get a .html file extension ?

Windows hides some file extensions by default.
Among them .html and .ini and .js and .txt and you may only see a file name without file extension.
You can check the file extension (file type) in the Properties of the file in Windows Explorer via the right-click context menu.

You can inspect the MIME database key with the registry editor (regedit.exe) and do a search for that MIME type (file extension) via Ctrl+F.
Be cautious with editing the registry as there is NO UNDO possible: all changes are applied immediately.
You can export key(s) in the registry editor before making changes.
You can check specific file extension keys (e.g. .jpg) in the registry with the registry editor.

• HKEY_CLASSES_ROOT\.xxx

You can check a possibly linked MIME type in the MIME Database registry key.

• HKEY_CLASSES_ROOT\MIME\Database\Content Type\

Hi thinkbp, what method are you using to save the file? For example:

• right-click the player > Save Audio As...
• load the MP3 in its own tab (stand-alone player) and save it from there (Ctrl+s)
• site sends it as a download, and Firefox pops up the Open/Save dialog
• some other method

Thanks for your responses. I right click and select "save as" and this box appears (see below). My only "save as" choices are "Firefox HTML" or "All Files." How can I save as MP3?

Barbara

Hi Barbara, if you change the name to "test.mp3" and save it, is it actually a valid MP3 file, or some intermediate page that gets saved?

(Note: adding the quotation marks around the name should override the system's inclination to tack on a .html extension to the file name.)

Thank you, Jscher2000! It worked. I very much appreciate your help.

Well, hmm, you shouldn't have to do that, but perhaps there is a site-specific reason for that. If you notice more of a pattern, maybe we can think of something easier.

You can still check the MP3 linked MIME database key in the registry editor like I posted above because that is in most cases the cause of Firefox adding the wrong file extension.

• HKEY_CLASSES_ROOT\.mp3 =>
  HKEY_CLASSES_ROOT\MIME\Database\Content Type\