What Are the Minimum Valid JSON Strings, and How Do Different Parsers Handle Them?

Determining Minimum Valid JSON

The JSON standard, as defined in RFC4627, strictly specifies a JSON text as a serialized object or array. Consequently, only two minimal valid JSON strings exist:

1. {} (empty object)
2. [] (empty array)

Exceptions and Adaptations

However, the introduction of ECMA-404 and adaptations in web browsers have expanded the definition of valid JSON. ECMA-404 permits the top-level JSONText to include any JSONValue, including strings, numbers, and null values.

Browsers integrate the JSON object (JSON.parse() and JSON.stringify()) in accordance with ES5, which further extends the definition of valid JSON. ES5 allows all JSON values to be accepted as valid input, irrespective of their placement as the root.

Implications for JSON Parsing

This divergence from the strict RFC4627 definition means that different JSON parsers may have varying interpretations of what constitutes valid JSON. For instance, browsers will accept simple values (strings, numbers, nulls), while parsers adhering to RFC4627 may reject anything other than objects and arrays as the root.

Therefore, when working with JSON, it is crucial to consider the target environment and the specific JSON parser being used to ensure the validity of JSON strings.

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