ImHex Looks amazing, but I couldn't get it to work on my system last time I tried. Not a pre built version and not compiling it myself. So I wrote myself a simple hex viewer. Only a viewer, don't need an editor. All other hex editors that I could get to work on my system where really disappointing. Either they couldn't handle large files (>2GB), or they lacked features, like decoding the bytes at the current location as various integer types, had very cumbersome controls for navigation, or displayed important information like the current offset in uneditable labels (status bar) and even didn't give it enough room for large files so it got cut off! Did they never use their own program? Anyway, my viewer only has a terminal interface, so you can always select and copy any text it displays. Also has IMHO handy controls to jump around to absolute and relative offsets. See: https://github.com/panzi/rust-hox
But don't look at the ugly code. I just cobbled it together somehow because I needed exactly that.
Your software seems to be in the same vein as hexyl. I can't personally vouch for how well it handles large files cause it's been a while, but I suspect it'll do alright.
I'm a fan of nhexl-mode in emacs. It does take a while to open large binaries (dozens of gigabytes), however I've managed to use it to do some rudimentary swapping out of video files on a modern computer game.
Examining binaries for firmware images I built when writing embedded software and for reverse engineering binaries by others to see how they work, make modifications. Fixing corrupted image files or figuring out how they work, examining Windows PE files or DLLs to get an overview of how they work. HxD for example can also do some limited calculations on the bytes as well as show you what CPU instruction they might represent. Sometimes a hex editor is useful for looking at data files stored as binary.
I also used a hex editor extensively when dumping the output of streaming H264 NAL units to figure out why the video was corrupted.
When working with non text file formats (e.g. coding a parser or file generator) hex editors are convenient for checking that data are where they're expected to be, finding out where they are otherwise, or checking what values they have. Even compressed file formats have header information that can be inspected if you have the format's specification.
