Downloaded JAR files are saved with the extension




5 years ago
4 months ago


(Reporter: ipatrol6010, Unassigned)


35 Branch
Windows 7

Firefox Tracking Flags

(Not tracked)



User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:35.0) Gecko/20100101 Firefox/35.0
Build ID: 20150122214805

Steps to reproduce:

I've tried downloading several jar files from various sources.

Actual results:

Firefox always saves them in the form <filename>

Expected results:

These files should be saved as .jar, which is the correct extension.
Also, take a look at the following URLs:

This would suggest the problem has existed for as long as four years. I assume the only reason it's never been brought up is that relatively few people download .jar files to save to disk.
Component: Untriaged → Downloads Panel
Hardware: x86_64 → All
Do you downloaded the files or opened them with an application ?
Do you have an example public link to such a jar file that produces this error ?
Flags: needinfo?(ipatrol6010)
I first noticed it with
Flags: needinfo?(ipatrol6010)
>HTTP request sent, awaiting response...
>  HTTP/1.1 200 OK
>  Server: LRBD-bigdownload-
>  Date: Sat, 14 Feb 2015 21:04:30 GMT
>  Connection: close
>  Accept-Ranges: bytes
>  Content-transfer-encoding: binary
>  Content-Length: 1410729
>  Content-Disposition: attachment; filename="DragonAPI 1.7.10 V4b.jar"
>  Content-Type: application/zip

The server tells us that this file is in fact a zip file with the content-type.
That the .zip extensions is added when you open the file with a helper application is expected.
Just downloading the file doesn't change the file extension for me with Firefox35 on Windows7.
The server interprets it as application/zip because a JAR is literally just a specially-structured ZIP file. I would suggest that FF should in this specific instance use the extension specified by the Content-Disposition and not the Content-Type. Now, some logic could be used so that, when an application/zip file is detected, to check the suggested filename and, if the extension is indeed a type of ZIP file, to give it the extension suggested there. I know several other typed of files, like most MS Office files, are also ZIPs, so perhaps this behavior could be applied to them too.
> I know several other typed of files, like most MS Office files, are also ZIPs, so perhaps this behavior could be applied to them too.
Firefox and all other good browsers don't check the content of the file because it's dangerous, forbidden by the http RFC and inconsistent.
The webserver tells us what kind of the it sends with the content-type header. The extension of the file doesn't matter from the browsers point of view. The browser looks and changes the extension only if you open a file with a helper application. The reason is simple: If you open a application/zip file with a helper application like 7-zip and the extension is for example .czf, the helper application can reject the file.

btw: The right content-type for jar files is afaik application/java-archive
I didn't suggest the file type handling of FF be affected by type-probing voodoo. I merely suggested that for save to disk operations, the default extension be based on the server-suggested filename unless something is grossly out of whack. The revised filename handler would be only triggered by an application/zip MIME type, and would therefore still be fundamentally following the server's lead, it would just use additional information to suggest an extension for the user to save it as.

Hi all,
This just happened to me and it is kind of embarassing. I am a long time fan of Firefox.
The link I used is not public so I could not share it but the file is download as .jar in Chrome while Firefox 66.0.2 (64 bit) added .zip to the file.
Hope this should identify and then be fixed and thank you.

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