> For the complete documentation index, see [llms.txt](https://harmonic-protocol-1.gitbook.io/documentation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://harmonic-protocol-1.gitbook.io/documentation/introduction.md).

# Introduction

#### What is Harmonic Protocol?

**Harmonic Protocol** is the first human-validated x402 trading protocol on Base.

It operates entirely through *x402 requests*.

Users submit their trades into a shared mempool. Anyone can validate them by solving a CAPTCHA and confirming the request.

Validators earn a portion of each transaction in USDC, creating an open, fair, and human-driven trading layer.

The protocol runs on **Base** and is completely **gasless** — no ETH required to trade.

***

#### What is x402?

The **x402 standard** allows on-chain actions to be represented as off-chain signed requests.

Instead of sending a transaction directly to the blockchain, a user signs a message authorizing the protocol to execute on their behalf.

This design makes trading on Harmonic:

* **Gasless** – users don’t pay ETH to sign.
* **Flexible** – requests can be queued, delayed, or prioritized by bribes.
* **Open** – anyone can choose to validate and execute them.

Harmonic builds a *mini human-layer mempool* on top of Base, where the community decides which trades go through first.


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