blank schema and validation - jsonschema

Question

If I have a blank JSON schema, such as
{}
and I try to validate the following data:
{
"hello": "world",
}
would validation be successful? (note the trailing comma).
I tried using everit json schema validator in java,
JSONObject rawSchema = new JSONObject(new JSONTokener("{}"));
Schema schema = SchemaLoader.load(rawSchema);
schema.validate(new JSONObject("{\"hello\" : \"world\",}"));
and it seems to validate.
Interestingly, some online validates this JSON
https://www.jsonschemavalidator.net/
whereas others don't
https://json-schema-validator.herokuapp.com/
The later uses a parser from Jackson before validating, perhaps that's the reason?

Answer 1

JSON Schema validates JSON. Technically, trailing commas are not valid JSON. However, many JSON ignore that and allow trailing commas. In general you're safer not having trailing commas in your JSON so you know it will work with all JSON parsers.
You are validating against the empty schema ({}). An empty schema means there are no constraints on what the value can be. An value that is valid JSON will be valid against this schema. Therefore, the only reason you would have validators reporting different results is if they disagree on whether it's valid JSON. If the validator uses a JSON parser that allows trailing commas, it will be valid, otherwise it will be invalid.