zip files

I am seeing some inconsistency in what happens when I download a zip file from my web site. The files are all uploaded as zip files using !FTPc but on the server they will, of course, simply have the ‘.zip’ filename extension.

Windows Firefox – downloads correctly
RISC OS Webster – is seen as an ‘Archive’ file before download, downloads correctly but ends up with a ‘Data’ filetype on completion of the download
VRPC Netsurf 3.10 – downloads as a ‘Data’ file either with or without the ‘/zip’ (choices)
ARMX6 Netsurf 3.10 – downloads as an XML file

Since Webster can see the file as an ‘Archive’ RISC OS filetype in the save dialogue window, presumably from the file extension ‘.zip’ and the Mimemap file, then RISC OS should be able to cope.

Zip files from other web sites, e.g. ArmSort, are downloaded on RISC OS from an identical HTML link of the form:

<A HREF="http://www.site.com/Filename.zip">Click to download</A>

but do download with the correct filetype with Netsurf. I am now very puzzled.

I tend to download my own software either using !Store under RISC OS or using Firefox under Windows (making sure I open the zip archive under RISC OS) so I may not have noticed this before.

Your server is probably serving the file with a MIME type of application/octet-stream or similar. This should be application/zip. How to configure this will vary depending on server software.

So there is nothing I can do about it? Why does it add a MIME type? I haven’t asked it to. Should I upload it with a ,xxx suffix to force the MIME type on RISC OS? Why does Webster see the correct filetype and Netsurf fail to do so?

How do I see what MIME type it has decided to add?

If I upload the file with a DDC (Archive) file type (vertical zig-zag) it still appears on the ftpc window (after uploading) with an a91 (Zip) filetype (horizontal zig-zag). So it looks like the server is choosing the MIME type itself from the file extension of ‘.zip’.

Sorry for the terseness of my earlier post.

So there is nothing I can do about it?

Most server software is configurable. If it’s being hosted by a third-party provider then they may provide a web interface for configuring it.

Why does it add a MIME type? I haven’t asked it to.

The HTTP spec requires every file to have one. If the server doesn’t know what to use then it’ll use a default one (usually application/octet-stream).

Should I upload it with a ,xxx suffix to force the MIME type on RISC OS?

I’ve never tried that so don’t know whether it’ll work. My gut feeling is that it’s not going to help, but there’s no harm in trying.

Why does Webster see the correct filetype and Netsurf fail to do so?

I’ve never used Webster but it’s possibly seeing the generic application/octet-stream type and looking up .zip → &A91 in the MimeMap database. I believe Firefox does something similar.

How do I see what MIME type it has decided to add?

I’m not sure off-hand. Something like Insomnia for Windows can show you, but that’d be overkill for a task like this.

Chris’s server is reporting that the files are

Content-Type: application/x-zip-compressed

so there’s clearly an entry in some of his MimeMap files which matches this, and not one in the mappings on his VRPC system.

Why does it add a MIME type? I haven’t asked it to.

Because without one, your browser won’t know what type the file is. Downloaded files don’t need an extension to have a type.

Should I upload it with a ,xxx suffix to force the MIME type on RISC OS?

No, because that won’t work. Your webserver won’t know about RISC OS type extensions, and that’s what’s doing this.

Why does Webster see the correct filetype and Netsurf fail to do so?

Perhaps it makes assumptions based on the filename extension?

How do I see what MIME type it has decided to add?

wget -S is the method I use, but the RISC OS port didn’t seem happy with that option when I last tried it (although I didn’t spend long looking into why).

So it looks like the server is choosing the MIME type itself from the file extension of ‘.zip’.

Correct. It will have a lookup table for extensions, to map them to MIME types.

My understanding of how FTPc works is that the file type info is removed on upload, leaving just the file extension. Viewing the uploaded file on FTPc uses the Mimemap module and, on my ARMX6, thus shows any .zip file as type a91 and will download it as such.

If a download is requested via an anchor link then the server (AIUI) decides on the type of file from its extension and uses its own version of MimeMap to specify a MIME type that is (almost) invisible which should ‘just work’, especially if it is IANA registered.

Chris’s server is reporting that the files are

Content-Type: application/x-zip-compressed

so there’s clearly an entry in some of his MimeMap files which matches this [application/x-zip-compressed], and not one in the mappings on his VRPC system.

Many thanks for this information.

Not quite true, neither matches exactly, but in any case that would not affect what other people are seeing as they cannot know what I have in my MimeMap files, nor from which computer I uploaded the zip file:

VRPC.!Boot.Choices.Default.Internet.Files.MimeMap contains

application/compress Archive ddc .Z .z "ZIVM " “ZIVM????”

application/gzip GZip f89 .gz .gzip .tgz "Gzip " “Gzip????” “ZIVUSITx”

application/x-compress Archive ddc

application/x-gzip GZip f89

application/zip Archive ddc .zip "ZIP " “ZIP ????”

application/zip Archive ddc .arc “BINAarc©” “mArcarc*”

application/zip Archive ddc .spk

# FIXME: Check for an arj filetype
application/x-arj Archive ddc .arj “BINADArj”

# FIXME: Check for an lha filetype
application/x-lzh Archive ddc .lha .lzh "LHA " “LHA ????”

ARMX6.!Boot.Resources.!Internet.files.MimeMap contains

application/gzip GZip f89 .gz .gzip .tgz

application/zip Zip a91 .zip

application/x-bzip2 BZip2 16e .bz2

application/x-compress Archive ddc

application/x-gzip GZip f89

application/x-zip Zip a91
# Not IANA registered, but prevalent

application/compress Archive ddc .z .arc .spk .lha .arj .lzh

application/bzip2 BZip2 16E .bz2

Adding an entry:
application/x-zip-compressed Zip a91
to the MimeMap file on my Titanium means that zip files from my web site are now downloaded with the the right file type on that computer.

Have you tried:
<a href="zipfile.zip" download="zipfile.zip">Download</a>
In your HTML document?

No.