nom vs Pest
Which should you use? A side-by-side look at what each one does, who it suits, what it costs, how hard it is to set up, and where each falls short.
Open source · MIT
A Rust library for building fast, safe parsers by combining small parsing functions.
Open source · MIT
A PHP testing framework with a simple, readable syntax, also aimed at AI agents.
The short answer
Choose nom if you need…
- Rust developers writing parsers for binary or text file formats
- Developers parsing network protocols or data that arrives in chunks
- Engineers prototyping a parser for a programming language or data format
- Developers who want parsers that are small, testable, and reusable
Choose Pest if you need…
- PHP developers who want to add automated tests to a project
- Teams already using PHP testing tools who want a more readable syntax
- Developers interested in a testing framework that works with AI agents
Side-by-side
| nom | Pest | |
|---|---|---|
| Type | Library | Library |
| Price | Free and open source | Free and open source |
| Licence | MIT | MIT |
| GitHub stars | 10.5k | 11.8k |
| Setup difficulty | Intermediate | Intermediate |
| How you get it | Install with a package manager | Install with a package manager |
| Main language | Rust | PHP |
| Last code update | 15 months ago | 4 days ago |
What each one is
nom
nom is a parser combinators library written in Rust. You build parsers by assembling small functions, such as 'take 5 bytes' or 'recognize the word HTTP', into larger patterns that look like the grammar they describe. It is designed for reading binary formats, text formats, and streaming data without copying input unnecessarily.
Pest
Pest is a testing framework for PHP, a language used to build many websites and web apps. It lets developers write automated tests that check whether code behaves as expected, using a concise, readable style. The README describes it as built for PHP developers and AI agents, but the README excerpt provided does not explain the features in detail.
Best for
nom
- Rust developers writing parsers for binary or text file formats
- Developers parsing network protocols or data that arrives in chunks
- Engineers prototyping a parser for a programming language or data format
- Developers who want parsers that are small, testable, and reusable
Pest
- PHP developers who want to add automated tests to a project
- Teams already using PHP testing tools who want a more readable syntax
- Developers interested in a testing framework that works with AI agents
Strengths
nom
- The README says it is designed to be fast and memory-safe, with benchmarks it reports as competitive with several other parser libraries and handwritten C parsers
- Parsers are assembled from small reusable pieces that are easy to test separately
- Error reporting can aggregate error codes and custom error types
Pest
- Free and open source under the MIT license
- Has a large community with over 11,000 GitHub stars
- Has official documentation at pestphp.com and an active release (v5.3.4)
Not ideal for
nom
- People who are not writing Rust code, since this is a Rust-only library
- Projects needing a ready-made tool that reads a grammar file and generates a parser, since nom is code you write by hand with combinators
- Beginners new to Rust, because the README's examples rely on Rust's type system and error handling
Pest
- Non-PHP developers, since it only works with the PHP language
- People who need install steps or setup details, since the provided README excerpt does not include them
Trade-offs
nom
- You write parsers in Rust code with combinator functions, which takes learning before it feels natural
- The README's documentation links point to external resources such as a guide and reference docs, so getting started depends on them
- The README notes a minimum Rust version of 1.65 and the latest series is referred to as 8.0, so check compatibility with your toolchain
Pest
- The README excerpt provided does not show code examples or detailed features, so the exact workflow is unclear from this source
- Limited to the PHP ecosystem
Getting started
Pest
Clone the repository
git clone https://github.com/pestphp/pestFrequently asked questions
What is the difference between nom and Pest?
nom: A Rust library for building fast, safe parsers by combining small parsing functions. Pest: A PHP testing framework with a simple, readable syntax, also aimed at AI agents. nom suits rust developers writing parsers for binary or text file formats, while Pest suits php developers who want to add automated tests to a project.
Are nom and Pest free?
nom: Free and open source. Pest: Free and open source.
Is nom or Pest more popular?
Pest has more GitHub stars (11.8k) than nom (10.5k). Popularity isn't the same as fit — check which one matches your use case above.
What are other alternatives to nom and Pest?
Other options people compare them with include G2.
Built from our catalogue entries for both products: open-source details come from each project's README (AI-assisted, refreshed weekly) and GitHub data; AI-tool details are editorial. Spotted something wrong? Let us know from either product's page.