If you open the CSV file via the address bar then you can prefix with the view-source: protocol.

If the file is downloaded from internet then maybe an extension helps.

• Open in Browser https://addons.mozilla.org/firefox/addon/open-in-browser/
• Open Link in Browser As... https://addons.mozilla.org/firefox/addon/open-link-in-browser-as/

thanks for the workaround using th prefix view-source: However, it's still pretty circuitous for me.

Is there no straight forward way using the firefox preferences or the file handlers.json ?

Firefox can't handle this file format (file extension), that is why you get tab opening repeatedly when you try this. You can use view-source to override this and show the file as plain text, otherwise you need to rename the file and add a .txt file extension.

thanks for the explanation!

would it make sense to file an enhancement request, or have there already been plenty of internal discussions regarding this text file topic? I do like using firefox also as an (addl.) file browser.