Quick Answer
The answer is JSON, or JavaScript Object Notation, which is the most common data format in REST API requests and responses for modern network automation. This is because JSON is lightweight, language-agnostic, and natively supported by virtually all programming languages and network devices, making it the de facto standard for exchanging structured data over HTTP. On the Cisco DevNet Associate 200-901 exam, this concept tests your understanding of REST API fundamentals, often appearing in questions about payload formatting or comparing JSON to XML or YAML. A common trap is assuming XML is still dominant due to legacy systems, but modern automation workflows—like those using Cisco NSO, Ansible, or Python scripts—rely on JSON for its compact structure and ease of parsing. Remember the memory tip: “Just Say No to XML” for REST APIs—JSON is the default choice for simplicity and speed.
This 200-901 practice question tests your understanding of infrastructure and automation. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which data format is most commonly used in REST API requests and responses in modern network automation?
YAML
Why wrong: YAML is used for configuration files, not typically for API payloads.
XML
Why wrong: XML is verbose and less common in modern APIs.
CSV
Why wrong: CSV is for tabular data, not API payloads.
JSON
JSON is the standard for REST APIs.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
JSON
JSON (JavaScript Object Notation) is the most commonly used data format in REST API requests and responses for modern network automation because it is lightweight, language-agnostic, and natively supported by most programming languages and network devices. REST APIs typically use JSON over HTTP due to its ease of parsing, compact structure, and alignment with web development practices, making it the de facto standard for exchanging structured data in automation workflows like those with Cisco NSO, Ansible, or Python scripts.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
YAML
Why it's wrong here
YAML is used for configuration files, not typically for API payloads.
XML
Why it's wrong here
XML is verbose and less common in modern APIs.
CSV
Why it's wrong here
CSV is for tabular data, not API payloads.
JSON
Common exam traps
The trap here is that candidates may confuse YAML's prevalence in configuration management (e.g., Ansible) with REST API data interchange, or assume XML's historical role in SOAP extends to modern REST, leading them to overlook JSON's dominance in actual API payloads.
Detailed technical explanation
JSON's structure directly maps to JavaScript objects, allowing seamless integration with web clients and server-side frameworks, and it is formally defined in RFC 7159. In practice, REST APIs often use JSON with HTTP Content-Type headers like 'application/json', and network automation tools such as Cisco DNA Center or Meraki APIs exclusively return JSON, enabling direct deserialization into dictionaries or objects in Python without custom parsers. A subtle behavior is that JSON does not support comments, which can be a limitation for documentation but ensures strict, unambiguous data exchange.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
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FAQ
Infrastructure and Automation — This question tests Infrastructure and Automation — Read the scenario before looking for a memorised answer..
The correct answer is: JSON — JSON (JavaScript Object Notation) is the most commonly used data format in REST API requests and responses for modern network automation because it is lightweight, language-agnostic, and natively supported by most programming languages and network devices. REST APIs typically use JSON over HTTP due to its ease of parsing, compact structure, and alignment with web development practices, making it the de facto standard for exchanging structured data in automation workflows like those with Cisco NSO, Ansible, or Python scripts.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
This 200-901 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-901 exam.
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