How LLMs Work: An Interactive Step-by-Step Guide to Language Model Mechanics

Repositoryw3cj/how-llms-workResource

The GitHub repository 'how-llms-work' by w3cj provides an interactive web application that explains the inner mechanics of large language models step by step. From pattern-matching chatbots to neural network backpropagation, BPE tokenisation, Word2Vec embeddings, and training a transformer from scratch, each stage includes locally runnable code.

Key points

  1. Step-by-step breakdown: Covers five core stages, including an ELIZA-style SSE chat, XOR backpropagation, Byte-Pair Encoding (BPE) from scratch, Word2Vec embeddings, and transformer training.
  2. Runs locally: The entire application runs locally on Node.js 20+ using pnpm.
  3. Lean web stack: Built with TypeScript, Hono (handling server routes, JSX rendering, and client components), and Vite for bundling.
  4. Interactive visualisation: Visualises algorithmic steps live, such as BPE merge stages and vector clustering in embeddings.

Why it matters

Many developers use LLM APIs as black boxes without grasping the foundational maths and mechanics. Projects like this make complex deep learning foundations tangible and accessible directly through standard web technologies.

Analysis

The project tackles the barrier of overly abstract machine learning textbooks by implementing core concepts in plain, runnable TypeScript. It is tailored for software engineers and students eager to demystify LLM architectures from first principles. Regarding maturity, it is an educational reference project (568 stars, 178 forks) rather than a production library, and currently lacks a declared open-source license.

Found in

Summary generated by AI (Gemini 3.8 Flash, 27 September 2026). It may contain errors – the original source is authoritative.

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Locations

  • Mattersburg
    Johann Nepomuk Bergerstraße 7/2/14
    7210 Mattersburg, Austria
  • Vienna
    Ungargasse 64-66/3/404
    1030 Wien, Austria

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