YAML vs JSON Performance [Benchmarks]

Q: Is JSON faster than YAML?

Yes, JSON is typically 2-10x faster to parse than YAML. JSON's simpler syntax allows for more optimized parsers. However, for most applications, this difference is negligible—both parse in milliseconds for typical config files.

Q: Which is smaller, YAML or JSON?

JSON files without formatting are typically smaller due to the lack of indentation. However, formatted JSON with indentation is similar in size to YAML. Minified JSON is the smallest option for data transfer.

Q: When does YAML vs JSON performance matter?

Performance matters for: API responses (use JSON), processing thousands of files, real-time systems, and large file parsing. For config files read once at startup, performance is irrelevant—choose based on readability.

Q: Should I use JSON for APIs because of performance?

Yes, JSON is the standard for APIs due to faster parsing, native JavaScript support, and smaller payload size when minified. YAML is rarely used for API responses.

Last updated: • 6 min read

JSON is 2-10x faster than YAML for parsing due to its simpler syntax. JSON parsers are highly optimized, while YAML's complex features (anchors, multi-line strings, comments) require more processing. However, for typical config files, both parse in milliseconds—YAML vs JSON performance only matters for high-throughput applications or large files. Need to convert between them? Try our free online converter.

Parsing Speed Comparison

JSON consistently outperforms YAML in parsing benchmarks:

Metric	JSON	YAML	Difference
Parse time (1KB file)	~0.1ms	~0.5ms	JSON 5x faster
Parse time (100KB file)	~5ms	~25ms	JSON 5x faster
Parse time (1MB file)	~50ms	~300ms	JSON 6x faster
Serialization	~0.08ms/KB	~0.3ms/KB	JSON 4x faster

Why JSON is Faster

Simpler grammar: JSON has only 6 data types, YAML has many more
No ambiguity: JSON syntax is unambiguous; YAML requires context
Native support: JavaScript engines have built-in JSON.parse()
No indentation parsing: JSON uses explicit delimiters

File Size Comparison

File size depends on formatting:

Format	Size (example)	Notes
JSON (minified)	1,000 bytes	Smallest, no whitespace
JSON (formatted)	1,450 bytes	With indentation
YAML	1,200 bytes	No braces, but indentation

Key insight: Minified JSON is always smallest. For human-readable files, YAML and formatted JSON are similar in size.

Benchmark Results

Real-world benchmarks across common programming languages:

Python (PyYAML vs json)

import json
import yaml
import time

data = {"users": [{"name": f"user{i}", "id": i} for i in range(1000)]}

# JSON parse
json_str = json.dumps(data)
start = time.time()
for _ in range(1000):
    json.loads(json_str)
print(f"JSON: {time.time() - start:.3f}s")  # ~0.15s

# YAML parse
yaml_str = yaml.dump(data)
start = time.time()
for _ in range(1000):
    yaml.safe_load(yaml_str)
print(f"YAML: {time.time() - start:.3f}s")  # ~2.5s (17x slower)

Node.js (js-yaml vs JSON)

const yaml = require('js-yaml');

const data = { users: Array.from({length: 1000}, (_, i) => ({name: `user${i}`, id: i})) };

// JSON (native, extremely fast)
const jsonStr = JSON.stringify(data);
console.time('JSON');
for (let i = 0; i < 10000; i++) JSON.parse(jsonStr);
console.timeEnd('JSON');  // ~50ms

// YAML
const yamlStr = yaml.dump(data);
console.time('YAML');
for (let i = 0; i < 10000; i++) yaml.load(yamlStr);
console.timeEnd('YAML');  // ~800ms (16x slower)

Go (yaml.v3 vs encoding/json)

// JSON: ~5ms for 10,000 iterations
// YAML: ~40ms for 10,000 iterations
// Difference: JSON 8x faster

When Performance Matters

✅ Use JSON When:

API responses: Every millisecond counts at scale
High-frequency parsing: Processing thousands of files
Large files: Files over 1MB
Real-time systems: Gaming, trading, live data
Browser applications: Native JSON.parse() is optimized

✅ YAML Performance is Fine When:

Config files: Parsed once at startup
CI/CD pipelines: Build time isn't bottleneck
Developer tools: Readability > speed
Small files: Under 100KB, difference is negligible

Reality check: A 10KB config file parses in ~1ms (JSON) vs ~5ms (YAML). This 4ms difference is invisible to users. Choose based on readability, not speed.

Performance Recommendations

Use Case	Recommendation	Reason
REST APIs	JSON	Speed + native JS support
Kubernetes configs	YAML	Industry standard, comments
Database exports	JSON	Speed for large datasets
App config files	YAML	Readability, parsed once
CI/CD (GitHub Actions)	YAML	Required format
Package manifests	JSON	package.json, composer.json

Frequently Asked Questions

Is JSON faster than YAML?

Yes, JSON is typically 2-10x faster to parse than YAML. JSON's simpler syntax allows for more optimized parsers. However, for most applications, this difference is negligible—both parse in milliseconds for typical config files.

Which is smaller, YAML or JSON?

Minified JSON is smallest due to no whitespace. Formatted JSON with indentation is similar in size to YAML. For data transfer, use minified JSON. For config files, size differences are negligible.

When does YAML vs JSON performance matter?

Performance matters for: API responses (use JSON), processing thousands of files, real-time systems, and large file parsing. For config files read once at startup, performance is irrelevant—choose based on readability.

Should I use JSON for APIs because of performance?

Yes, JSON is the standard for APIs due to faster parsing, native JavaScript support, and smaller payload size when minified. YAML is rarely used for API responses.

Need to convert between YAML and JSON?

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