XO
Enforce strict JavaScript happiness style code formatting.
Pricing
Free tier
Flat rate
Adoption
→StableLicense
Open Source
Data freshness
Aging · Jun 8, 2026Overview
What is XO?
XO is a tool that enforces the JavaScript happiness style for consistent and clean code. It helps developers maintain a uniform coding standard across projects, ensuring readability and ease of maintenance.
Key differentiator
“XO stands out by focusing solely on the JavaScript happiness style, offering a simple and effective way to enforce this specific coding standard across projects.”
Capability profile
Capability Radar
Honest assessment
Strengths & Weaknesses
↑ Strengths
↓ Weaknesses
XO is primarily designed for JavaScript and has limited functionality or no direct support for other programming languages.
Extensive configuration options and the need to understand ESLint rules deeply to customize XO effectively can lead to a steep learning curve.
XO may slow down significantly when running linting on very large projects, impacting developer productivity.
The documentation is good for basic usage but falls short in explaining more complex configurations and integrations with other tools.
Fit analysis
Who is it for?
✓ Best for
JavaScript developers who need to enforce a consistent coding standard.
Teams working on large-scale projects where uniformity is crucial for maintainability.
✕ Not a fit for
Projects that require support for multiple programming languages beyond JavaScript.
Developers looking for real-time code style enforcement within an IDE without additional setup.
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 XO
Step-by-step setup guide with code examples and common gotchas.