Comparison
YAML vs JSON: which for configuration?
YAML or JSON for your next config file? Benchmarks, readability, tooling, security, and a clear recommendation for modern projects.
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TL;DR
For config files humans edit: YAML (with a linter in CI). For config files generated by a program or consumed by browsers / APIs: JSON. Consider TOML if you want strict types without YAML's indentation traps.
Option A
YAML
Readable, comment-friendly
Option B
JSON
Fast, strict, universal
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Side-by-side
| Axis | YAML | JSON |
|---|---|---|
| Human readability | Excellent | Good |
| Comments | Yes (`#`) | No |
| Multi-line strings | Native (`|`, `>`) | Escaped only |
| Trailing commas | N/A | Error |
| Anchors / reuse | Yes (`&`, `*`) | No |
| Indentation | Load-bearing | Irrelevant |
| Parse speed | Slower | Faster |
| Security (untrusted input) | Use `safe_load` | Inherently safe |
| IDE support | Good (YAML LS + schemas) | Excellent, universal |
| Industry tools | K8s, CI/CD, Ansible | package.json, tsconfig, API responses |
The honest verdict
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When YAML is worth the friction
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When JSON is the safer bet
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Hybrid approach: JSON with comments (JSONC)
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Frequently asked questions
What does Kubernetes actually prefer?
Both — `kubectl apply -f` happily accepts JSON or YAML. Humans write YAML manifests; generators and operators emit JSON. Under the hood, the API server converts to JSON either way.
Can I use YAML for `package.json`?
No — npm requires JSON specifically. Some tools (pnpm, yarn) let you use `package.yaml`, but compatibility with the wider ecosystem suffers.
Which format does GitHub Actions use?
YAML only, and it leans heavily on YAML's multi-line string support (`run: |`) and anchors for reusable steps.
How do I convert between them safely?
Use our /convert/json-to-yaml/ and /convert/yaml-to-json/ pages — fully client-side, so your secrets never leave the browser.