JSON vs YAML vs XML: Which Data Format Should You Use?
JSON, YAML, and XML all describe structured data, but they are tuned for different jobs. Pick the wrong one and you get friction: a config file no human wants to edit, or an API payload no parser can read. Here is the practical breakdown — and a free converter for every direction.
At a glance
| Format | Readability | Comments | Common use | FreeToolset tool |
|---|---|---|---|---|
| JSON | Good (for machines) | No | Web APIs, config consumed by code, NoSQL storage | JSON Formatter, Validator |
| YAML | Best (for humans) | Yes | CI/CD, Docker, Kubernetes, app config files | YAML → JSON |
| XML | Poor (verbose) | Yes | Legacy enterprise, SOAP, Office/docs, RSS | XML → JSON, Formatter |
JSON — the web's default
JSON is strict and unambiguous: keys must be quoted, no trailing commas, no comments. That rigidity is why every programming language parses it natively and why it dominates REST APIs. Use it whenever data crosses a network or a language boundary.
- Use JSON when: building an API, storing documents in a database, or exchanging data between services.
- Avoid it when: a human will hand-edit the file often — the lack of comments and rigid syntax gets tedious.
YAML — config that humans tolerate
YAML drops most punctuation in favor of indentation and adds comments. That makes it the go-to for configuration files (GitHub Actions, Docker Compose, Kubernetes manifests). The trade-off: indentation is meaningful, so a stray space breaks the file.
- Use YAML when: writing config that people maintain by hand.
- Avoid it when: the data is consumed by a system that doesn't already speak YAML — convert to JSON first.
XML — verbose but battle-tested
XML carries schemas, namespaces, and attributes, which made it the enterprise standard before JSON. It is still everywhere in legacy systems, SOAP services, and document formats. It is verbose, but its tooling is mature.
- Use XML when: interfacing with older enterprise systems or document standards that require it.
- Avoid it when: you are starting something new — JSON or YAML will be lighter.