[Bug] text/markdown custom file validation not working

[YaroBear]

Is there an existing issue for this?

• I have searched the existing issues

Have you updated FilePond and its plugins?

• I have updated FilePond and its plugins

Describe the bug

I want to restrict file uploads to only Markdown (.md) files. However, since most browsers do not reliably detect the MIME type for .md files, I understand that a custom fileValidateTypeDetectType function is required. The custom validation function provided does not work as expected.

Reproduction

• Set the acceptedFileTypes property to ".md" which limits the file picker to only select files with the .md extension
• Resolve "text/markdown" or "text/plain" for the fileValidateTypeDetectType
• Get "File is of invalid type" error message

See this codesandbox: https://codesandbox.io/p/devbox/friendly-butterfly-pxqm92?workspaceId=ws_PrPLhqSkCsZkRf6v6g8FR1

Environment

- Device: Macbook Pro M3
- OS: MacOS 15.3.1
- Browser: Firefox Developer Edition, Edge, and Safari

[rikschennink]

Hi,

The acceptedFileTypes requires a mime type, not an extension.
https://pqina.nl/filepond/docs/api/plugins/file-validate-type/#properties

In this case you can set ['text/markdown'], then in the fileValidateTypeDetectType you return 'text/markdown' when the extension is '.md'