An overview of the fundamental principles and steps for securely transferring tokens from the Ethereum mainnet to the Polygon network.
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How to Bridge Tokens from Ethereum to Polygon
A technical guide to transferring assets between Ethereum mainnet and the Polygon PoS network.
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core-concepts
Core Bridge Concepts
01
Token Locking & Minting
The lock-and-mint mechanism is the foundation of most token bridges. When bridging from Ethereum to Polygon, your original tokens are securely locked in a smart contract on Ethereum, and an equivalent, pegged representation is minted on Polygon.
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Locking: Your ERC-20 tokens (e.g., USDC, WETH) are sent to a verifiable vault contract on Ethereum.
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Minting: An identical amount of Polygon-native tokens (e.g., USDC.e, WETH) are created on the Polygon chain for you to use.
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Security: This ensures the total supply across both chains remains constant, backed by the locked collateral.
02
Proof-of-Stake Bridge
Polygon's native Proof-of-Stake (PoS) Bridge is the official, recommended method for transferring assets. It uses a set of validators to secure the bridge and confirm transactions between chains.
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Process: Users deposit funds into the PoS bridge contract on Ethereum, which validators observe to mint tokens on Polygon.
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Withdrawals: To move assets back, you initiate a burn on Polygon and provide proof to the Ethereum contract.
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Use Case: Ideal for standard ERC-20 tokens, ETH, and NFTs, offering a balance of security and relatively fast withdrawals (approx. 3 hours).
03
Plasma Bridge for Security
The Plasma Bridge provides enhanced security for specific assets like MATIC and ETH by using a separate fraud-proof framework. It's designed for maximum safety but involves a longer withdrawal period.
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Mechanism: Assets are secured by a series of child blockchains (Plasma chains) with periodic commitments to Ethereum.
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Challenge Period: Withdrawals have a 7-day challenge window to allow for fraud proofs, making them very secure but slower.
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Purpose: Best suited for moving large amounts of foundational assets where security is the absolute top priority over speed.
04
Bridging Process Steps
Successfully bridging tokens involves a clear, multi-step user journey from initiating the transfer to using funds on Polygon.
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Step 1 - Connect: Connect your Web3 wallet (like MetaMask) to the bridge interface and ensure it's set to the Ethereum network.
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Step 2 - Approve & Deposit: Approve the bridge contract to spend your token, then deposit it. Wait for Ethereum confirmations.
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Step 3 - Claim on Polygon: After a short wait, switch your wallet to the Polygon network and 'claim' your minted tokens to your address.
05
Bridged Token Standards
Understanding the different token representations is crucial. Tokens on Polygon exist as either native assets or bridged versions with distinct contract addresses.
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Bridged Tokens (e.g., USDC.e): These are minted by the bridge and are backed 1:1 by locked Ethereum assets. They are the direct result of using the PoS bridge.
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Native Tokens (e.g., USDC): Some assets, like USDC, have been natively issued on Polygon by the original issuer. These are distinct from bridged versions.
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Importance: Always verify the token contract address in your wallet to know which type you hold, as liquidity and compatibility can differ.
06
Gas Fees & Confirmation Times
The bridging experience is defined by costs and wait times on both the source and destination chains, which vary by bridge type.
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Ethereum Gas: You must pay an Ethereum gas fee to approve and deposit your tokens. This can be high during network congestion.
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Polygon Gas: Claiming and using your bridged tokens requires minimal MATIC for Polygon gas fees.
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Timeline: Deposits to Polygon typically take 20-30 minutes. Withdrawals back to Ethereum via the PoS bridge take about 3 hours, while Plasma withdrawals take 7 days.
Step-by-Step Bridge Process
A detailed guide to securely transferring tokens from the Ethereum mainnet to the Polygon PoS network using the official Polygon Bridge.
1
Step 1: Connect Wallet & Select Assets
Prepare your wallet and choose the tokens you wish to bridge.
Detailed Instructions
First, navigate to the official Polygon Bridge portal (bridge.polygon.technology). Ensure you are on the correct site to avoid phishing scams. Connect your Web3 wallet, such as MetaMask, by clicking the 'Connect Wallet' button and selecting your provider. Once connected, the interface will display your Ethereum mainnet balance. You must then select the token you wish to bridge from the dropdown menu. Popular choices include MATIC, USDC, or WETH. For this example, we will bridge USDC. It is crucial to verify that you have sufficient ETH in your wallet to cover the gas fees for the Ethereum transaction, which can vary but often range from $10 to $50 depending on network congestion.
- Sub-step 1: Go to bridge.polygon.technology and click 'Connect to a Wallet'.
- Sub-step 2: Select and authorize your wallet (e.g., MetaMask) in the pop-up window.
- Sub-step 3: From the 'Select Token' menu, choose 'USDC' and enter the amount you wish to transfer.
Tip: Always double-check the token contract address on the bridge interface against a trusted source like the Polygon documentation to ensure you are interacting with the correct asset.
2
Step 2: Initiate the Transfer on Ethereum
Approve and confirm the bridge transaction on the Ethereum network.
Detailed Instructions
After entering the amount, you will initiate a two-transaction process. The first transaction is an ERC-20 approval, which grants the bridge contract permission to move your tokens. You must sign this approval in your wallet, which will incur an ETH gas fee. Once approved, you can proceed to the deposit transaction. This is the main action that locks your tokens in the Ethereum bridge contract and signals the Polygon validators to mint them on the other side. When confirming this transaction, pay close attention to the gas fees displayed in your wallet; you may adjust the gas price based on urgency. The transaction will be submitted to the Ethereum network, and you must wait for block confirmations (typically 10-20 blocks) for finality.
- Sub-step 1: Click 'Transfer' and confirm the token approval transaction in your wallet pop-up.
- Sub-step 2: After approval, click 'Transfer' again to confirm the main deposit transaction.
- Sub-step 3: Monitor the transaction status on a block explorer like Etherscan using the provided TX hash.
Tip: Use a gas tracker like GasNow to choose an optimal gas price. Setting it too low may cause the transaction to stall for hours.
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Step 3: Wait for Checkpoint & Minting
Allow time for the cross-chain state synchronization and token minting on Polygon.
Detailed Instructions
This step is automatic but requires patience. The Ethereum-Polygon bridge uses a checkpoint mechanism. Validators bundle your transaction with others into a Merkle root, which is periodically submitted from the Polygon sidechain to the Ethereum mainnet. This process, called state synchronization, typically takes 7-8 minutes but can be longer during high traffic. You do not need to take any action here, but you can track progress. The bridge UI will show status updates like 'Waiting for Checkpoint' and 'Minting on Polygon'. Once the checkpoint is verified on Ethereum, the Plasma or PoS bridge contract (depending on the asset) instructs the MintableAssetProxy on Polygon to mint the equivalent tokens. These newly minted tokens are PoS-wrapped assets (e.g., posUSDC) on the Polygon network.
- Sub-step 1: Keep the bridge tab open or note your transaction ID to check back later.
- Sub-step 2: Use the 'Track Transfer' feature on the bridge site with your TX hash.
- Sub-step 3: Observe the status change from 'Checkpoint Submitted' to 'Minted on Polygon'.
Tip: Bridging via the PoS bridge is faster (7-8 mins) than the Plasma bridge (which can take ~3 hours for challenge periods). The interface indicates which bridge type you are using.
4
Step 4: Verify & Use Assets on Polygon
Confirm the receipt of tokens and interact with the Polygon network.
Detailed Instructions
Once the bridge UI shows completion, you must actively verify the tokens in your wallet. First, switch your wallet's network to the Polygon Mainnet. In MetaMask, you can add it via Chainlist or manually with the following RPC details: Network Name: 'Polygon Mainnet', RPC URL: 'https://polygon-rpc.com', ChainID: 137, Symbol: 'MATIC', Block Explorer: 'https://polygonscan.com'. After switching, your bridged tokens may not appear automatically. You need to import the token contract address for the bridged asset. For example, the PoS USDC contract address on Polygon is 0x2791Bca1f2de4661ED88A30C99A7a9449Aa84174. Add this as a custom token in MetaMask to view your balance. Finally, you can now use your assets on Polygon's DeFi ecosystem, such as providing liquidity on QuickSwap or lending on Aave Polygon Market.
- Sub-step 1: In MetaMask, click the network selector and choose 'Polygon Mainnet' or add it manually.
- Sub-step 2: Import the token by clicking 'Import tokens', pasting the correct contract address, and adding it.
- Sub-step 3: Confirm your balance matches the bridged amount minus any fees on the Polygon explorer.
Tip: Always keep a small amount of MATIC on Polygon to pay for transaction fees on the network. You can acquire some via a centralized exchange that supports Polygon withdrawals or a fiat on-ramp.
Bridge Method Comparison
Comparison of methods to bridge tokens from Ethereum to Polygon
| Feature | Polygon PoS Bridge | Hop Protocol | Across Protocol | Orbiter Finance |
|---|---|---|---|---|
Time to Finality | ~45 minutes | ~15 minutes | ~2-5 minutes | ~1-3 minutes |
Avg. Cost (ETH → MATIC) | $5-15 | $2-8 | $1-5 | $0.50-3 |
Supported Assets | ETH, ERC-20 tokens | ETH, USDC, USDT, DAI | ETH, USDC, USDT, DAI, WBTC | ETH, USDC, USDT, DAI, WBTC |
Security Model | Ethereum + Plasma/PoS | Optimistic Rollup + Bonded Relayers | Optimistic Oracle + UMA | ZK-Rollup + Multi-Sig |
Native Token Required | MATIC for gas | No | No | No |
Withdrawal Delay | Up to 7 days (checkpoint) | Instant (via liquidity pools) | Instant (via relayers) | Instant (via liquidity) |
Bridge Type | Official Canonical Bridge | Liquidity Network | Cross-Chain Intents | Decentralized Rollup Bridge |
Technical Perspectives
Understanding the Bridge
Token bridging is the process of moving digital assets from one blockchain network, like Ethereum, to another, such as Polygon. Think of it as sending a valuable item through a secure, specialized postal service between two countries. The original token is locked in a smart contract on Ethereum, and an equivalent, representative token is minted on Polygon.
Key Points
- Two-Way Street: Bridges are bidirectional. You can move assets to Polygon (often called "depositing" or "bridging") and later bring them back to Ethereum ("withdrawing" or "un-bridging").
- Representative Tokens: On Polygon, you receive a wrapped asset (e.g., WETH or USDC.e) that is pegged 1:1 to the value of your original token on Ethereum.
- Use Case - Lower Fees: The primary reason to bridge is to escape Ethereum's high gas fees. Once on Polygon's Proof-of-Stake chain, transactions like swapping on QuickSwap or lending on Aave become extremely cheap and fast.
Example Process
When using the official Polygon PoS Bridge, you connect your wallet (like MetaMask), select the token and amount, and approve two transactions. The first approves the bridge contract, and the second locks your tokens. After a short wait (about 20-30 minutes for checkpoint finality), your funds appear in your wallet on the Polygon network.
Frequently Asked Questions
Bridging tokens from Ethereum to Polygon involves a two-step transaction process that locks tokens on one chain and mints equivalent tokens on the other. First, you initiate the transfer on the Ethereum mainnet, which sends your assets to a secure smart contract. This contract locks your tokens. Then, a relayer service or validator network on Polygon confirms this lock and mints a wrapped or canonical version of your token on the Polygon PoS chain. The entire process relies on state sync mechanisms and typically takes 7-8 minutes for standard bridges like the PoS Bridge. For example, sending 100 USDC from Ethereum results in receiving 100 USDC.e (the canonical bridged version) on Polygon, ready for use in DeFi protocols like Aave or Quickswap.