Is there an online simulator that would allow me to step through, debug, or simulate the execution of a Bitcoin script?
I know of these two:
The second one in particular I have found to be very useful.
Bitcoin Script debugging utilities.
This is a set of tools used to debug or construct scripts for use in Bitcoin.
btcdeb> help step Execute one instruction and iterate in the script. rewind Go back in time one instruction. stack Print stack content. altstack Print altstack content. vfexec Print vfexec content. exec Execute command. tf Transform a value using a given function. print Print script. help Show help information.
The github repository for the first link posted by StephenM347 can be found here
If you want to run it locally, clone the repo and then,
Launch a server from here. This will launch a server on port 8000.
python -m SimpleHTTPServer 8000
From the browser, visit localhost:8000, and select the file