Across

# Across Protocol Documentation > Across Protocol is a crosschain interoperability protocol powering fast, low-cost token transfers across 23+ chains. > Three settlement mechanisms: Intents (relayer network), CCTP (USDC), and OFT (USDT). > API base URL: https://app.across.to/api ## Introduction - [Actors in the System](https://docs.across.to/introduction/actors): The key participants that make crosschain transfers work — users, relayers, LPs, dataworkers, and the UMA oracle. - [API Keys & Integrator ID](https://docs.across.to/introduction/api-keys): How to get an API key and integrator ID for production use of the Across APIs. - [Audits](https://docs.across.to/introduction/audits): Security audits of the Across Protocol and UMA smart contracts. - [Bug Bounty](https://docs.across.to/introduction/bug-bounty): Report vulnerabilities and earn rewards through the Across Protocol bug bounty program. - [Deposit Addresses](https://docs.across.to/introduction/deposit-addresses): Generate a counterfactual deposit address that users can send funds to in order to initiate a crosschain transfer. - [Direct Route Linking](https://docs.across.to/introduction/direct-route-linking): Link users directly to a pre-filled bridge route on the Across UI. - [Technical FAQ](https://docs.across.to/introduction/faq): Frequently asked questions about integrating Across Protocol. - [Key Features](https://docs.across.to/introduction/features): What makes Across the fastest, cheapest, and most secure crosschain interoperability protocol. - [Fees in the System](https://docs.across.to/introduction/fees): How LP fees, relayer fees, gas fees, and capital fees are calculated in Across. - [Hyperliquid Withdrawals](https://docs.across.to/introduction/hypercore-withdrawals): Withdraw from Hyperliquid (HyperCore) to any Across-supported chain via a gasless multi-signature flow. - [Working with Hypercore](https://docs.across.to/introduction/hypercore): Bridge assets to Hyperliquid's sub-second settlement layer via Across. - [Welcome to Across](https://docs.across.to/introduction): Crosschain interoperability with ~2 second fills across all major chains. - [Refunds](https://docs.across.to/introduction/refunds): How refunds work when a crosschain transfer expires without being filled. - [Across for Stablecoins](https://docs.across.to/introduction/stablecoins): Move native USDC, USDT0, and USDH across chains with a single Swap API call. - [Introduction to Swap API](https://docs.across.to/introduction/swap-api): The unified entry point for all crosschain operations on Across. - [Tracking Deposits](https://docs.across.to/introduction/tracking-deposits): Monitor crosschain transfer status using the deposit tracking API. - [Why Across](https://docs.across.to/introduction/why-across): The fastest, cheapest, and most secure way to move assets across chains. - [Relayer Nomination](https://docs.across.to/introduction/relayers/relayer-nomination): How exclusive relayer nomination works and how to participate. - [Running a Relayer](https://docs.across.to/introduction/relayers/running-relayer): Set up and operate your own Across V3 relay infrastructure. - [Disputing Root Bundles](https://docs.across.to/introduction/security/disputing-root-bundles): How to challenge invalid bundle proposals — manually or with automated tooling. - [Security Model and Verification](https://docs.across.to/introduction/security): How Across secures crosschain transfers through optimistic verification, bonds, and UMA's oracle. - [Validating Root Bundles](https://docs.across.to/introduction/security/validating-root-bundles): How root bundles are validated and what the verification process checks. - [Deposit ETH into Aave](https://docs.across.to/introduction/embedded-actions/deposit-eth-aave): Swap to ETH crosschain and deposit directly into Aave's lending pool. - [Add Liquidity to Across HubPool](https://docs.across.to/introduction/embedded-actions/hubpool-liquidity): Swap to ETH and add liquidity to t […gekürzt]