explaingit

antlr/antlr4

★ 18,879JavaAudience · developerComplexity · 4/5MaintainedLicenseSetup · easy

TLDR

ANTLR generates parsers from grammar rules, letting you build custom languages, config formats, and domain-specific tools that can read and understand structured text.

Mindmap

mindmap
  root((ANTLR))
    What it does
      Generates parsers
      Builds parse trees
      Creates visitor code
    Input and output
      Grammar files
      Parser code
      Target languages
    Use cases
      Custom languages
      Config file readers
      Compilers
      Query languages
    Tech stack
      Java 11+
      10 target languages
      Parse tree walkers

Things people build with this

USE CASE 1

Build a custom scripting language for your application with its own syntax and rules.

USE CASE 2

Parse and validate proprietary data formats or configuration files in your system.

USE CASE 3

Create a compiler or interpreter for a domain-specific language used in your industry.

USE CASE 4

Analyze code or structured text by walking the parse tree to extract meaning and react to specific patterns.

Tech stack

JavaPython 3C#GoJavaScriptTypeScriptC++Swift

Getting it running

Difficulty · easy Time to first run · 5min
Use freely for any purpose, including commercial use, as long as you keep the copyright notice and license text.

In plain English

ANTLR (ANother Tool for Language Recognition) is a tool that helps developers create their own programming languages, configuration file formats, or any other structured text that a computer needs to read and understand. The core idea is this: you write a "grammar", a set of rules describing what valid input looks like, and ANTLR automatically generates the code that can read and interpret that input. This generated code is called a parser. Think of it like teaching a computer to read a new language from a rulebook. Once the parser exists, it builds a tree-like structure (a "parse tree") representing the meaning of what was read, and ANTLR also generates helper interfaces that let you walk through that tree and react to specific parts. You would use ANTLR when building a custom scripting language for your app, reading a proprietary data format, writing a compiler or interpreter, or processing complex configuration files. It powers real-world tools like query languages, code analysis tools, and domain-specific languages used in enterprise systems. ANTLR 4 supports 10 target languages, meaning the parser it generates can be written in Java, Python 3, C#, Go, JavaScript, TypeScript, C++, Swift, Dart, or PHP. The tool itself is written in Java and requires Java 11 or higher to run.

Copy-paste prompts

Prompt 1
I need to create a parser for a custom configuration file format. Show me how to write a grammar file in ANTLR and generate a Java parser from it.
Prompt 2
How do I use ANTLR to build a simple scripting language that my app can execute? Walk me through the grammar, parser generation, and visitor pattern.
Prompt 3
I want to generate a Python parser from an ANTLR grammar. What are the steps and how do I use the generated code to parse input?
Prompt 4
Show me how to write an ANTLR grammar for a query language, then walk the parse tree to extract and execute the query.
Prompt 5
How do I handle errors and provide helpful error messages when parsing fails with ANTLR?
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Generated 2026-05-18 · Model: sonnet-4-6 · Verify against the repo before relying on details.