The settings.json file is where the GUI settings are stored and it's modified automatically by bitcoin-qt when you save the Options dialog. It has a format like this:
{
...Ignore this line, it's just to show the setting names and their values look like "name": "value"....
}
If you get the error
Failed loading settings file that means your settings.json has the incorrect format.
We're going to reset the GUI options by removing all the values in the file, and with it (hopefully) the error.
1. First make a copy of the settings.json file in case we accidentally mess it up.
2. Now we're going to replace the entire contents of the original file with this:
{
}
This is what an empty settings.json with the default values looks like. Then you should be able to start Bitcoin Core again and set your previous settings again from the options dialog.
