FMS Installer Overwrites Custom MIME Types

We’ve been getting our servers updated to Claris FileMaker Server 19.4.2 recently and noticed an aspect of the install that it might help others to be aware of. We were using the built in FMWebSite that FileMaker Server installs to allow downloads of an IPA file for testing on a mobile device. This requires defining a couple of custom MIME types in the web server configuration, .plist and .ipa. The FMS installer appears to overwrite the FMWebSite configuration, at least on Windows, and reset the MIME types to the defaults, removing the .ipa and .plist entries we’d created. 

We first noticed it when one of our ‘over the air’ app installs started failing and the only recent change had been updating the server from FMS  to FMS When we recreated the custom MIME type entries the installs were successful again.

Curious to see if our hunch was accurate, we set up a test to confirm. Directly before upgrading another server, from FMS to FMS, we added .ipa and .plist types. Immediately after the upgrade, those types were gone.

Has anyone else experienced this scenario? Do you know of documentation from Claris concerning this topic? Send us a message below.


Claris saw our post in the Community forum and forwarded the details to Testing and Development. They confirmed the behavior and said they will continue to look into the issue.

The FMWebSite will be overwritten starting with version 19.2.1, the first version that initially supported upgrade installations on FileMaker Server. MIME-types are overwritten with the default settings even if the MIME-type is modified in Internet Information Service (IIS) Manager. The issue also occurs on macOS, the mime.types.2.4 file is replaced with the default file even if MIME-type is modified in the file. Also, mime_type.json file gets replaced by the default file.

For further learning:

What is a MIME Type?

BobCares explains that MIME – Multipurpose Internet Mail Extensions – helps identify the type of data and helps in identifying the nature and format of a document. MIME format includes a MIME content type and subtype which denotes the type of data in the file.

MDN Web Docs explains that browsers use the MIME type, not the file extension, to determine how to process a URL, so it’s important that web servers send the correct MIME type in the response’s Content-Type header. If this is not correctly configured, browsers are likely to misinterpret the contents of files, sites will not work correctly, and downloaded files may be mishandled.

Where Do MIME Types Come From?

The Internet Assigned Numbers Authority. IANA was founded by Jonathan B. Postel, “an American computer scientist who made many significant contributions to the development of the Internet, particularly with respect to standards”, according to Wikipedia. Some IANA functions date back to the 1970’s.  

Thank you for reading! We’d love to hear your thoughts or how we can be of assistance with your FileMaker questions or development needs.

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