Information from Aleksey:
I think --show=types could do the job: the first format in the first
line with 1+ formats listed is the default one. But it is in jumbo
only.

On a big file with 120k hashes, it takes 3 minutes 20 seconds to get the result from --show=types on my vm with only 2 cores . However, to get the default format from magnum idea #61 was instantaneous (I didn't time it but it was less than a second). Should we stick with #61 to show the default format faster to the user ?

I understand. In this case it's best to relay this information back on the list and then close this ticket.

@Math07 can you please write this piece of info back to the original thread on john-dev, Aleksey might think of this as useful. You can then close this ticket.

I sent it to the list, I'll wait for answer.

This still have the advantage that once you get the format list, you can deduce yourself the default format when user uncheck/check a row without reusing CPU. However, the result takes a lot longer to arrive on big hash file. Maybe if one day someone work on caching in QSettings the format for each row and use that if the last modified date of the file didn't change, otherwise recall --show=types, this could be cool for at least two reasons for big files.