Can json have duplicate keys?

While JSON syntax technically allows duplicate keys in objects, it is strongly discouraged and considered bad practice. When an object contains duplicate keys, the behavior is undefined in the JSON specification. Most parsers will keep only the last occurrence of a duplicate key, silently discarding earlier values. This can lead to unexpected data loss and bugs that are difficult to debug. Some JSON validators will flag duplicate keys as errors, while others accept them with warnings. Different programming languages and JSON libraries handle duplicates inconsistently, making code unpredictable. Always ensure your JSON objects have unique keys to maintain data integrity, predictability, and compatibility across different systems and parsers.