EasyExperience level: 0-2 years · 3-5 years1 min read

JSON vs XML — Interview Questions

Reviewed by Gurusankar M.

Asked inInfosysTCSDeloitteCognizant
#json#xml#comparison#data format#markup
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Short Answer

JSON represents data as key/value objects and arrays; XML uses nested tags with optional attributes. JSON is less verbose, has native data types (number/boolean/null), and maps directly to objects, while XML supports attributes, comments, namespaces, and mature schema validation (XSD). JSON is lighter for APIs; XML suits document-centric or legacy/SOAP systems.

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Concept Made Simple

Coffee Chat Question

“What are the key structural differences between JSON and XML?”

Remember It Faster

Mind Map Answer

Structure
JSON: objects/arrays · XML: nested tags
Verbosity
JSON lighter · XML has open/close tags
Types
JSON has number/bool/null · XML all text
Extras
XML: attributes, comments, namespaces, XSD

Learn by Doing

Hands-on Keyboard

xml
<!-- XML -->
<user id="101">
  <name>Guru</name>
  <skills>
    <skill>Java</skill>
  </skills>
</user>

<!-- JSON equivalent -->
<!-- { "id": 101, "name": "Guru", "skills": ["Java"] } -->

Think Beyond the Expected

What If?

XML has attributes and comments — does JSON have an equivalent?

No. JSON has no attributes (everything is a key/value), no comments, and no namespaces. If you need those — say, rich document markup or strict enterprise schema validation — XML is a better fit. For most API payloads, JSON's simpler model is an advantage, not a limitation.

Real World

Teams migrating SOAP/XML services to REST usually switch to JSON for smaller payloads and easier client parsing, but keep XML where a partner mandates SOAP or where documents need XSD validation.

Interviewer's Expectation

Keywords they're listening for:

  • objects/arrays vs nested tags
  • JSON less verbose
  • JSON native types
  • XML attributes/namespaces/XSD
  • pick by use case

Common Mistakes

  • Saying XML is 'obsolete' (still used in SOAP/enterprise)
  • Forgetting JSON has no comments/attributes
  • Assuming both have the same type support

Best Practices

  • Choose JSON for web/mobile APIs
  • Keep XML for document markup, SOAP, or XSD needs
  • Validate JSON with JSON Schema when structure matters

Follow-up Questions

  1. Why did JSON replace XML for most web APIs?
  2. When is XML still the right choice?
  3. How do you validate JSON without XSD?

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Plain-language foundations

I'm preparing for a software engineering interview and want to understand this from scratch, as a beginner.

Topic: JSON vs XML (JSON)
Interview question: "What are the key structural differences between JSON and XML?"

Please:
1. Explain the core idea in simple, plain language, using an everyday analogy.
2. Define any technical terms you use.
3. Walk through one small, concrete example.
4. Finish with a single sentence I can easily remember.

Keep the tone friendly and assume I'm new to this topic.
Open inChatGPTGeminiClaude

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