Definition
JSON (JavaScript Object Notation) is a text-based data-interchange format that is both human-readable and machine-parseable. It supports six data types (string, number, boolean, null, array, object) and uses curly braces for objects and square brackets for arrays. JSON started in the JavaScript community but is now language-agnostic - every major programming language has fast JSON parsers built in or easily available.
JSON's popularity comes from simplicity. It is easier to read than XML, easier to produce, and parses much faster. Nearly every modern web API accepts and returns JSON by default, and JSON has effectively replaced XML as the default API data format.
How SheetLinkWP relates to JSON
SheetLink Forms serializes every form submission into a JSON payload before sending to your Apps Script webhook. The payload has a flat structure: fields as top-level keys, metadata (UTMs, timestamp, submission ID) as separate keys, and no nested objects so the Apps Script side can write columns directly without recursive flattening. CRM Fan-Out uses JSON for every downstream API call (HubSpot, Salesforce, Zoho, Pipedrive all accept JSON natively).