PEG.js vs Nearley

Side-by-side — pricing, strengths, tradeoffs, and fit.

PEG.js

Simple parser generator for JavaScript with fast parsers and excellent error reporting.

Nearley

Simple, fast, powerful parsing for JavaScript.

At a glance

Open SourceFree Tier
◌ Declining·From $0
Open SourceFree Tier
◌ Declining·From $0

Overview

One-liner

Simple parser generator for JavaScript with fast parsers and excellent error reporting.

One-liner

Simple, fast, powerful parsing for JavaScript.

Maturity

Declining

Maturity

Declining

Open source

✓ Yes

Open source

✓ Yes

Pricing

Free tier

✓ Available

Open source — free to use

Free tier

✓ Available

Open source — free to use

Starts at

$0

Starts at

$0

Model

Flat rate

Model

Flat rate

Enterprise

✕ None

Enterprise

✕ None

Best for

✓ Best for

JavaScript developers who need to parse complex grammars efficiently and with clear error messages.
Projects requiring custom syntax parsing, such as DSLs or configuration files.

✓ Best for

JavaScript developers who need to implement grammars and parsing logic in their projects
Teams working on complex data transformation tasks that require robust parsing capabilities
Projects where custom language or format support is necessary and performance is a concern

Not ideal for

✕ Not for

Scenarios where a full-fledged parser generator like ANTLR is required due to its more extensive feature set.
Real-time data processing tasks that require extremely low latency and high throughput.

✕ Not for

Developers looking for a full-fledged natural language processing library (Nearley focuses on context-free grammars)
Users who need real-time parsing in high-throughput systems (Nearley may not be optimized for such scenarios)

Strengths

↑ Strengths

Generates fast parsers from PEG grammars
Provides excellent error reporting for easier debugging
Simple and easy to use API
Supports JavaScript ES6+ features

↑ Strengths

Simple and easy-to-use parser generator for JavaScript
Supports context-free grammars
Fast parsing capabilities
Extensive documentation and community support

Weaknesses

↓ Weaknesses

Limited integrations with other ecosystems
Complex setup for non-trivial grammars
Performance issues with large input sizes
Documentation lacks depth for advanced use cases

↓ Weaknesses

Limited language support
Complex setup for non-trivial grammars
Performance issues with large inputs
Small community and limited third-party support
Full PEG.js profile →Full Nearley profile →
PEG.js vs Nearley | AI Navigator