JSON vs XML: Complete Comparison
The choice between JSON and XML is one of the fundamental decisions in data format selection. While JSON has largely won the web API battle, XML remains relevant in many contexts.
Size Comparison
JSON is significantly smaller than XML for the same data. XML requires opening and closing tags for every element. This overhead compounds with nested data. Size matters for network transfers and storage. Real-world measurements show JSON is typically 30-50% smaller than equivalent XML. However, both formats compress well with gzip.
Readability
JSON excels at representing structured data with clear hierarchy. XML shines when data has rich textual content mixed with structure. XML's self-describing nature can aid readability with explicit tag names. Ultimately, readability depends on the data type. For API data, JSON is typically more readable. For documents with mixed content, XML can be clearer.
Parsing Speed
JSON parsing is faster in most implementations. JSON parsing in JavaScript is essentially free. XML parsing requires handling elements, attributes, namespaces, and more complexity. Memory usage differs too. DOM XML parsing requires more overhead. For most applications, the differences are negligible compared to network latency.
When to Use Which
Use JSON for REST APIs, configuration files in JavaScript ecosystems, document databases, and client-side storage. Consider XML for document-oriented content, when required by existing systems (SOAP), configuration with comments, when schema validation is critical, and data needing transformation with XSLT. For most new projects, start with JSON unless you have specific requirements favoring XML.
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