> ## Documentation Index > Fetch the complete documentation index at: https://developers.circle.com/llms.txt > Use this file to discover all available pages before exploring further. > ## Agent Instructions > Before reading these docs, install the relevant Circle Skill to get pre-loaded context — skills are LLM-optimized and cover architecture decisions, correct flows, and common pitfalls. In Claude Code: run /plugin marketplace add circlefin/skills then /plugin install circle-skills@circle. With Vercel Skills CLI: run npx skills add circlefin/skills. Available skills: use-usdc https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-usdc/SKILL.md (balances, transfers, approvals on EVM and Solana); EURC has no skill — see https://developers.circle.com/stablecoins/what-is-eurc.md; bridge-stablecoin https://github.com/circlefin/skills/blob/master/plugins/circle/skills/bridge-stablecoin/SKILL.md (crosschain transfers via CCTP, USDC, EURC, and third-party assets); use-arc https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-arc/SKILL.md (Arc chain config, contract deployment, USDC bridging — Arc docs: https://docs.arc.io/llms.txt); use-circle-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-circle-wallets/SKILL.md (choose wallet type); use-developer-controlled-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-developer-controlled-wallets/SKILL.md (custodial wallets for payouts and treasury); use-user-controlled-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-user-controlled-wallets/SKILL.md (embedded wallets with Web2 login); use-modular-wallets https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-modular-wallets/SKILL.md (smart contract wallets with passkeys and ERC-4337); use-gateway https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-gateway/SKILL.md (unified USDC balance, nanopayments); use-smart-contract-platform https://github.com/circlefin/skills/blob/master/plugins/circle/skills/use-smart-contract-platform/SKILL.md (deploy, interact, monitor contracts). Pair any skill with the Circle MCP server for live SDK signatures, contract addresses, and chain IDs: {"mcpServers":{"circle":{"url":"https://api.circle.com/v1/codegen/mcp"}}}. > Read the product overview first. Each product has an overview explaining when and why to use it. Read it before quickstarts. > Pick the right wallet type. Developer-controlled (you hold keys), user-controlled (end user holds keys via PIN/social login), or modular (smart contract wallets with passkeys). See https://developers.circle.com/wallets.md. > Use CCTP V2 for crosschain transfers. CCTP natively transfers USDC and EURC via burn-and-mint, and supports permissionless wrapping of third-party assets via lock-and-mint. V1 is legacy; always use V2 unless V1 is specified or the chain requires it (Noble, Sui, and Aptos still require V1). Migration guide: https://developers.circle.com/cctp/migration-from-v1-to-v2.md. > Use Bridge Kit for frontend bridging. Wraps CCTP with a simpler SDK for user-facing apps. Use CCTP directly for backend transfers. > Gas Station vs Paymaster. Gas Station sponsors gas for Circle Wallet transactions. Paymaster lets users pay gas in USDC. Different use cases — read both overviews. > Gateway Nanopayments for sub-cent payments. Gasless USDC micropayments down to $0.000001 via x402 and batched settlement. For pay-per-request APIs, AI agent payments, streaming. > Look up USDC addresses per chain. Never hardcode — use https://developers.circle.com/stablecoins/usdc-contract-addresses.md. > Prefer SDKs over raw API calls. Node.js and Python SDKs handle auth, retries, and errors. > API key required. Bearer token in Authorization header. Testnet and mainnet use separate keys and may use different base URLs depending on the product. > Set up webhooks when available. Most operations are async. Webhooks deliver transaction confirmations and state changes. > When calling list endpoints, paginate using pageSize and pageAfter until no nextPageAfter cursor is returned—stopping at the first page silently misses records. > Building an AI agent? Start with the Agent Stack—Circle CLI, agent wallets, and nanopayments built for autonomous use cases: https://developers.circle.com/agent-stack.md. # Circle Wallets > Add secure, embedded wallets to your application with Circle's APIs and SDKs. Manage keys, sign transactions, and support multiple blockchains. Circle Wallets helps you add secure, embedded wallets to your application so your users can hold and use digital assets without the usual complexity of keys, infrastructure, and chain-specific details. You integrate using REST APIs or Web and Mobile SDKs (Android and iOS). ## Key features Circle Wallets gives you the building blocks to ship embedded wallets without running key infrastructure or blockchain nodes yourself. You don't manage raw private keys. Circle secures keys with MPC or passkeys depending on wallet product; you get APIs to create wallets, sign transactions, and authorize actions. Key backup, rotation, and recovery are built in so you can focus on your app logic. One integration surface for REST APIs and Web or Mobile SDKs (Android and iOS). Create wallets, send transfers, and run contract calls from your backend or client. Same patterns across developer-controlled, user-controlled, and modular wallets based on the supported feature set for each product. Circle handles broadcasting, indexing, and balance and event data for supported chains. You don't run or maintain nodes. For chains where full infrastructure is not offered, use Signing APIs with your own node. Support for multiple chains and token types (including ERC-20, ERC-721, ERC-1155 on EVM and SPL on Solana). Unified addressing on EVM so one wallet can share the same address across chains. See [Supported blockchains](/wallets/supported-blockchains) and [Token IDs](/wallets/tokens) for details. ## Products You create and operate wallets for your users. Best when you need to move funds or run actions on their behalf (for example, payouts or automation). Your users control their own wallets inside your app, with familiar sign-in (social, email, or PIN). Best when users should own and approve every transaction. Your users control their wallets with passkeys and optional modules, like gasless. Best when you need passkey-based custody and flexible account configuration. Sponsor network fees so your users don't need to hold native tokens. Set policies and pay gas with your credit card. Let users pay gas fees with USDC instead of native tokens using Circle's permissionless ERC-4337 paymaster contracts. Automate transaction screening for AML and CTF compliance. Define rules, manage allowlists and blocklists, and review alerts. ## Get started The right wallet product depends on who controls the wallet: | Custody model | Best for | Product | | :- | :- | :- | | You control the wallet | Payouts, automation, backend-initiated actions | [Developer-controlled wallets](/wallets/dev-controlled) | | Your users control the wallet with familiar sign-in | Consumer apps where users approve transactions | [User-controlled wallets](/wallets/user-controlled) | | Your users control the wallet with passkeys | Apps requiring phishing-resistant auth and account modules | [Modular wallets](/wallets/modular) | Confirm blockchain support and account type compatibility before you start building. Compare wallet products and account types (EOA, SCA, MSCA) to find the right fit for your application. Check which blockchains and tokens are available for each wallet product. ## Explore key topics Explore the following topics as you build. They apply to all wallet products. How transactions are initiated, authorized, and signed across wallet types. Run multiple operations in one request for supported wallet types and chains. How keys are secured (MPC vs passkeys), who controls them, and node hosting options. Broadcasting, indexing, gas, and bundling; how Circle runs wallet infrastructure.