When using the org-attach function on macOS the IDs are that are created are uppercase. It is possible to change the folder name to lowercase via (advice-add #'org-attach-id-uuid-folder-format :filter-return #'downcase) but the format in the ID property remains uppercase.


org attachment relative location (after adding the above advice): data/3e/8bb725-3fb7-4f3f-80b2-baa4369a48ce/example.pdf

snippet from org file:

** Example                                                             :ATTACH:
   :ID:       3E8BB725-3FB7-4F3F-80B2-BAA4369A48CE

On macOS I can still open the attachment because of filesystem case-insensitivity. However on Linux if you try to open the attachment, no corresponding ID can be found. I would like all org-attach IDs to be lowercase in both the folder name and its reference. How can I accomplish this?

Edit: uuidgen is used on macOS and Linux for me, and org-id-new/ org-id-get-create/uuidgen always returns an uppercase ID on macOS and lowercase ID on Linux.

  • In my (Fedora 33 linux) system, ID's are lower case. You need to figure out what method you are using to generate IDs and go from there. Start by evaluating (org-id-new) in your *scratch* buffer and seeing what it gives you. It's likely that the uuidgen executable is used: try it from the command line and see what it gives you. Edit your question and add that information to it.
    – NickD
    Nov 5, 2021 at 15:33

2 Answers 2


Are you wedded to using uuidgen? Org-mode has its own internal functions to generate uuid's, which will be used if you customize org-id-method to org. See C-h v org-id-method RET.


Alternatively, on MacOS write a uuidgenlc script that downcases the output of the "real" uuidgen and set

(setq org-id-uuid-program "/path/to/uuidgenlc")

uuidgenlc could be as simple as

#! /bin/bash

uuidgen | tr A-Z a-z

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