Hi.
You just need to include the library like this in the platformio.ini of your project:

lib_deps = arduino-libraries/Arduino_JSON @ 0.1.0

If you search on the library tab for “arduino_json“. It is the third result.
Regards,
Sara

Thank you Sara. Yes I guess I didn’t offer enough information I did do that. In fact in one instance I downloaded the complete file folders for the “multiple outputs” exercise in the Web Server book. Not making any changes, I got errors that the libraries could not be found. I then deleted all the files associated with that project and imported them via import button on the PIO screen. That time all worked however there were other errors relating to comments in a json file
{
“resource”: “/c:/Users/flagt/Documents/PlatformIO/Projects/test/.vscode/c_cpp_properties.json”,
“owner”: “_generated_diagnostic_collection_name_#0”,
“code”: “521”,
“severity”: 8,
“message”: “Comments are not permitted in JSON.”,
“startLineNumber”: 1,
“startColumn”: 1,
“endLineNumber”: 1,
“endColumn”: 3
}
I don’t quite understand where that’s comming from or why. 
I’ve also seen errors relating to SPIFFS being deprecated even though littleFS is being used.
For me at least, it seems the learning curve for Platformio is steeper than other IDEs when it comes to ooperational functions. I’ve been searching for tutorials but much of what I find either doesn’t go into explanation or (like) from the authors; way over my head.

Hi.
 
I’m not sure why you get that error related with the library. Maybe it would be better if you post or search that issue on the PIO forum, as I don’t know how to help with that: https://community.platformio.org/
 
As for the LittleFS issue, it is because even though we’re using LittleFS, the AsyncWebServer library still uses SPIFFS. That’s why you get that message – it’s not an error and you don’t need to worry about that.
 
Regards,
Sara