> ## Documentation Index
> Fetch the complete documentation index at: https://docs.pfbridge.xyz/llms.txt
> Use this file to discover all available pages before exploring further.

# Liquidity ads: how the ProofBridge marketplace works

> A liquidity ad is an on-chain offer from a Maker to provide cross-chain liquidity. How ads are created, reserved, locked, and settled in v2.

A liquidity ad is the on-chain offer that makes peer-to-peer bridging
possible. When a Maker posts an ad, they're committing liquidity in a
specific token on one chain against deposits of a specific token on
another. Bridgers pick the route that matches their transfer.

## What a liquidity ad contains

* **The route** — which token a Bridger deposits, and which token (on
  which chain) the Maker provides. Tokens exchange **1:1 by value**;
  amounts are aligned across differing token decimals automatically
  ([decimal scaling](/concepts/decimal-scaling)).
* **Pool amount** — the total liquidity the Maker has escrowed
* **Min / max per trade** — optional limits
* **Ad ID** — the identifier orders and proofs reference

These live on-chain in the `AdManager` contract; the app's routes are
built from them.

## Ad lifecycle

<Steps>
  <Step title="Create + fund">
    The Maker submits `createAd` and escrows the pool. Only funded ads
    serve orders.
  </Step>

  <Step title="Reserved by an order">
    A Bridger creates an order against the ad — the matching slice of the
    pool is **reserved** before any money moves. Reservations from orders
    that never fund expire after \~30 minutes and release automatically,
    so abandoned checkouts can't strand liquidity.
  </Step>

  <Step title="Locked for the order">
    Once the Bridger's deposit confirms, the Maker locks the reserved
    liquidity on-chain (`lockForOrder`) — the Maker's deposit into this
    trade. Both deposits are appended to their chain's Merkle Mountain
    Range.
  </Step>

  <Step title="Co-signed">
    Both parties sign the settlement with their
    [settlement keys](/v2/concepts/settlement-keys) — the trade cannot
    settle without both signatures.
  </Step>

  <Step title="Settled">
    Background workers combine the signatures, prove both deposits, and
    submit the unlocks. Each chain verifies the aggregated signature and
    the proof, then releases funds to the respective recipients.
  </Step>

  <Step title="Closed">
    After open trades settle, the Maker can close the ad and reclaim the
    remaining pool. Unlocked funds can be withdrawn at any time.
  </Step>
</Steps>

## Available vs pool

The amount a new order can take is the on-chain pool **minus the holds of
open trades** (reservations + locks). The [Manage ads](/v2/guides/manage-ads)
guide covers funding, withdrawing, and the ad statuses.

<Warning>
  Don't close an ad while trades are in progress — locked amounts stay
  reserved until their trades settle.
</Warning>

## What prevents double-spends

Each settlement consumes a **nullifier** — a one-time value bound to the
trade and side. Once recorded on-chain, any replay of the same proof is
rejected, independently on each chain. Together with the side-bound MMR
leaves and the co-signed roots, a deposit settles exactly once, in exactly
one direction, with both parties' consent.