ExplainThisRepo

The fastest way to understand any unfamiliar codebase using real project signals. Not blind AI guessing. Signals first. LLM second

ExplainThisRepo analyzes real project signals; configs, entrypoints, manifests, dependencies graph, structures and high-signal files producing a clear, structured EXPLAIN.md that shows you what the codebase actually does, how it is organized, where to start, what to ignore, and what matters before touching unfamiliar codebases.

Key Features

• Understand any GitHub repository in seconds
• System map that shows you where to start, what to ignore, what matters and why
• Deterministic repo signal extractor that feeds LLMs correctly.
• Speeds up understanding of unfamiliar codebases
• Solves the "garbage in, garbage out" problem specifically for codebases
• Multiple modes (quick, simple, detailed) that translates complex repository structure and code signals into architectural summaries. Not blind AI guessing. Signals first. LLM second
• Works with GitHub repositories, local repositories, GitHub directories, local directories, GitHub files and local files
• Supports private repositories and monorepos
• Zero-cloning and remote analysis
• Extract architecture signals from configs, entrypoints, and manifests
• Outputs the explanation to an EXPLAIN.md file in your current directory, prints it directly in the terminal, or a specified output file (.txt, .pdf, .docx, .md)
• Additional tools: stack detection, repo map

Installation

ExplainThisRepo supports multiple installation methods:

• pip (Python package)
• npm (prebuilt native binaries)
• .NET global tool
• standalone binaries

Quick install

pip

pip install explainthisrepo

Alternatively,

pipx install explainthisrepo

npm

npm install -g explainthisrepo

Alternatively

npx explainthisrepo owner/repo

.NET

dotnet tool install -g ExplainThisRepo

Run

explainthisrepo owner/repo

After installation, use any of the available command names:

explainthisrepo owner/repo
explain-this-repo owner/repo
etr owner/repo
explain owner/repo

Replace owner/repo with the GitHub repository identifier (e.g., facebook/react, torvalds/linux).

For full installation instructions, platform-specific notes, standalone binaries, and advanced setup: docs/INSTALLATION.md

Flexible Input Types

Accepts various formats for repository input, full GitHub URLs (with or without https), owner/repo format, issue links, query strings, and SSH clone links

explainthisrepo https://github.com/owner/repo
explainthisrepo github.com/owner/repo
explainthisrepo https://github.com/owner/repo/issues/123
explainthisrepo https://github.com/owner/repo?tab=readme
explainthisrepo git@github.com:owner/repo.git
explainthisrepo owner/repo/path/to/directory
explainthisrepo owner/repo/path/to/file.py
explainthisrepo .
explainthisrepo ./path/to/directory
explainthisrepo ./path/to/file.py

GitHub repo inputs are normalized internally to owner/repo.

Configuration

ExplainThisRepo supports multiple LLM models:

• Gemini
• OpenAI
• Ollama (local or cloud-routed)
• Anthropic
• Groq
• OpenRouter

Use the built-in init command to configure your preferred model:

explainthisrepo init
# or npx explainthisrepo init

For details about how initialization works, see docs/INIT.md.

To install support for specific models:

pip install explainthisrepo[gemini]
pip install explainthisrepo[openai]
pip install explainthisrepo[anthropic]
pip install explainthisrepo[groq]

GitHub token Access (Private Repos & Rate Limits)

ExplainThisRepo supports GitHub authentication for:

• Accessing private repositories
• Higher API rate limits on public repositories

explainthisrepo init

For step-by-step instructions, see docs/GITHUB_TOKEN.md

Flag options

• (no flag) → Full repository explanation written to EXPLAIN.md

• --quick → One-sentence summary

• --simple → Short, simplified explanation

• --detailed → Deeper explanation including structure and architecture

• --stack → Tech stack breakdown from repo signals

• --map → System map for understanding a codebase before changing it

• --version → Check installed CLI version

• --help → Show usage guide

• --doctor → Check system health and active model diagnostics

• --llm → Override provider selection

• --output / -o → Specify output file or directory (default: EXPLAIN.md)

CLI aliases

ExplainThisRepo ships with multiple command names that all map to the same entrypoint:

• explainthisrepo → primary command
• explain-this-repo → readable alias
• etr → short alias for faster typing
• explain → to figure out when overwhelmed in unfamiliar codebase
• ExplainThisRepo → useful name command for backup
• explain-this / explainthis → fun word play command

All three commands run the same tool and support the same flags and modes.

Model selection

The --llm flag selects which configured model backend to use for the current command.

explainthisrepo owner/repo --llm gemini
explainthisrepo owner/repo --llm openai
explainthisrepo owner/repo --llm ollama
explainthisrepo owner/repo --llm anthropic
explainthisrepo owner/repo --llm openrouter
explainthisrepo owner/repo --llm groq

--llm works with all modes (--quick, --simple, --detailed).

Command line usage

Default

Writes a full explanation to EXPLAIN.md:

explainthisrepo owner/repo
#e.g. explainthisrepo vercel/next.js

Quick mode

Prints a one-sentence summary to stdout:

explainthisrepo owner/repo --quick
# explainthisrepo facebook/react --quick

$ explainthisrepo vercel/next.js --quick

Next.js is a React framework that provides server-side rendering,
file-based routing, API routes, and build tooling for fullstack
web applications.

---

Detailed mode

Writes a more detailed explanation of repository structure and architecture:

explainthisrepo owner/repo --detailed

---

Simple mode

Prints a short, simplified explanation to stdout. No files are written.

explainthisrepo owner/repo --simple

---

Stack detector

Tech stack breakdown detected from repo signals. No LLM calls are made.

explainthisrepo owner/repo --stack

Repo map

Navigation system map for understanding unfamiliar codebases that shows you where to start, what matters and what to ignore before touching it:

explainthisrepo owner/repo --map
explainthisrepo . --map

By default, repo map mode writes to REPO_MAP.md.

The map focuses on:

• where to start reading
• the likely main flow through the project
• important files and why they matter
• visible architecture boundaries
• files or folders to ignore first
• open questions that cannot be determined from repo signals

Local Directory Analysis

ExplainThisRepo can analyze local directories directly in the terminal, using the same modes and output formats as GitHub repositories

explainthisrepo .
explainthisrepo ./path/to/directory

This works with all existing modes:

Details

explainthisrepo . --quick
explainthisrepo . --simple
explainthisrepo . --detailed
explainthisrepo . --stack
explainthisrepo . --map

When analyzing a local directory:

• Repository structure is derived from the filesystem
• High signal files (configs, entrypoints, manifests) are extracted locally
• No GitHub APIs calls are made
• All prompts and outputs remain identical

This allows analysis of projects directly from the local filesystem, without requiring a GitHub repository.

File Analysis

ExplainThisRepo analyzes individual files directly

explainthisrepo ./path/to/file.py

Supports all explanation modes:

Details

explainthisrepo ./file.py --quick
explainthisrepo ./file.py --simple
explainthisrepo ./file.py --detailed

When analyzing a file:

• The file is read safely with encoding and size limits
• Structure and basic signals (size, lines, type) are extracted
• The explanation focuses on purpose, logic, and behavior
• This makes it easy to understand unfamiliar files without scanning entire repositories.

GitHub File Analysis

ExplainThisRepo can analyze a single file directly from a GitHub repository without cloning it.

explainthisrepo owner/repo/path/to/file.py

Supports all explanation modes:

Details

explainthisrepo owner/repo/path/to/file.py --quick
explainthisrepo owner/repo/path/to/file.py --simple
explainthisrepo owner/repo/path/to/file.py --detailed

When analyzing a GitHub file:

• The file is fetched directly via the GitHub API
• Raw bytes are passed into a unified ingestion pipeline
• Binary detection, decoding, and size limits are handled in one place
• File ingestion is identical to local file analysis
• The explanation focuses on the file’s purpose, logic, and behavior
• This removes divergence between local and GitHub file handling

Input format must be:

explainthisrepo owner/repo/path/to/file

This is different from local file analysis:

explainthisrepo ./path/to/file.py

GitHub Directory Analysis

ExplainThisRepo can analyze a specific directory inside a GitHub repository without cloning it.

explainthisrepo owner/repo/path/to/directory

Supports all explanation modes:

Details

explainthisrepo owner/repo/path/to/directory --quick
explainthisrepo owner/repo/path/to/directory --simple
explainthisrepo owner/repo/path/to/directory --detailed

When analyzing a GitHub directory:

• Directory contents are fetched via the GitHub API
• Only structure and metadata are used (no full repo fetch)
• Signals include files, subdirectories, and extension distribution
• The explanation focuses on the directory’s role and structure

--stack is not supported for directory targets.

Custom output

--output, -o → Specify output file or directory (default: EXPLAIN.md)

Write to a specific file:

explainthisrepo owner/repo --output notes.md

Write to a nested path:

explainthisrepo owner/repo --output path/to/file.md

Write to a directory (creates EXPLAIN.md inside):

explainthisrepo owner/repo --output path/to/directory

Version

Check the installed CLI version:

explainthisrepo --version

Diagnostics

Use the --doctor flag to verify the environment, network connectivity, and API key configuration:

explainthisrepo --doctor

Termux (Android)

ExplainThisRepo supports Termux on Android.

For installation notes, PATH setup, Gemini support, and mobile-specific recommendations: see docs/TERMUX.md

Philosophy

I built this project with a personal motivation: my mum makes me fall in love with life again. That feeling of mental clarity, simplicity, grounded understanding and appreciation is what I wanted to bring into how developers understand codebases.

I believe understanding code should feel less overwhelming and more approachable. If this tool still makes you feel overwhelmed when reading code, I failed.

Special Thanks

• @Spectra010s for implementing the initial Node.js version of ExplainThisRepo and improving installation support for mobile environments like Termux
• @HalxDocs for implementing the --detailed mode for deeper architectural explanations
• @Manuel-Technologies for implementing the .NET global tool launcher and NuGet distribution support

Contributions

Contributions are welcome!

If you find a bug, have an idea, or want to improve the tool:

• See CONTRIBUTING for setup and guidelines
• Open an issue for bugs/feature requests
• Or submit a pull request for fixes/improvements

License

This project is licensed under the MIT License. See the LICENSE file for details.

Author

Caleb Wodi

• Email: caleb@explainthisrepo.com
• LinkedIn: @calchiwo
• Twitter: @calchiwo