UltraJSON
A fast JSON decoder and encoder written in C with Python bindings.
Pricing
Free tier
Flat rate
Adoption
→StableLicense
Open Source
Data freshness
Aging · Jun 8, 2026Overview
What is UltraJSON?
UltraJSON is a high-performance library for encoding and decoding JSON data. It's designed to be faster than the standard Python json module, making it ideal for applications where speed is critical.
Key differentiator
“UltraJSON stands out for its speed and efficiency in JSON processing, making it a go-to choice for developers who need to optimize their application's performance without sacrificing Python's ease of integration.”
Capability profile
Capability Radar
Honest assessment
Strengths & Weaknesses
↑ Strengths
↓ Weaknesses
UltraJSON is primarily a Python library with bindings in C, limiting its use outside the Python ecosystem.
UltraJSON may struggle with deeply nested or large JSON objects, leading to potential performance degradation or errors.
UltraJSON focuses on speed and does not include additional features like pretty-printing, schema validation, or object hook functions available in more comprehensive JSON libraries.
Fit analysis
Who is it for?
✓ Best for
Developers working on high-performance Python applications that require fast JSON parsing and generation.
Projects where the standard json module's speed is a bottleneck.
✕ Not a fit for
Applications where ease of use is prioritized over performance, as UltraJSON requires more setup than the built-in json module.
Scenarios where compatibility with non-Python environments is necessary.
Cost structure
Pricing
Free Tier
Available
Open source — free to use
Starts at
$0
Model
Flat rate
Enterprise
None
Performance benchmarks
How Fast Is It?
Ecosystem
Relationships
Next step
Get Started with UltraJSON
Step-by-step setup guide with code examples and common gotchas.