Question: Is there a way to control the order in which files appear in a gist? They don't seem to be alphabetical or chronological. I'd like to have a README.md appear as the first file in [a multi-file gist](https://gist.github.com/Sinetheta/6003037), but no amount of "deleting" a file and re-adding it seems to change anything.

Is there an order to these files that I'm not seeing, or does GitHub maintain an internal filetype priority list?

Answer: 
Since at least 2018, the order is [alphabetical, with periods and numbers coming before letters.](https://github.com/isaacs/github/issues/195)

That is, as mentioned in [Andrew D.Bond](https://stackoverflow.com/users/3442232/andrew-d-bond)'s [answer](https://stackoverflow.com/a/61832468/6309):

1. `$`
2. `.` (dot)
3. Numbers
4. Leading space (although the space doesn't appear after saving, the sort order is still updated)  

(although bis, in Sept. 2020, [IvanaGyro](https://stackoverflow.com/users/6663588/ivanagyro) adds [in the comments](https://stackoverflow.com/questions/17665267/how-do-you-control-the-order-in-which-files-appear-in-a-github-gist/17668995?noredirect=1#comment112988123_17668995) leading spaces will not affect the order any more)
5. `_` (underscore)
6. Letters (case insensitive)

Around 2013-2014 a [different order](http://en.wikipedia.org/wiki/ASCIIbetical_order) was used. See [Andrew D. Bond](https://stackoverflow.com/users/3442232/andrew-d-bond)'s [answer](https://stackoverflow.com/a/61832468/6309) for more.
As mentioned by @VonC in his answer, the order is asciibetical. Quick solution would be to prefix all files with numbers indicating the order in which you wish the files to appear, example 0\_, 1\_, 2\_, ... 9\_. Note, this solution will not work beyond 9 files as 10\_ will appear before 2\_. In that case, two digits need to be used 00\_, 01\_, 02\_, ..., 09\_, 10\_, 11\_, ... This can be generalized to any number of digits in the number of files. Although, it seems less likely, to me, that more more than 10 files to be shared in a gist.