Cross-Chain Bridging
Understanding how assets move between Ethereum and Polygon networks.
What is Cross-Chain Bridging?
Cross-chain bridging allows you to transfer assets between different blockchain networks. In Polygon's case, the bridge connects Ethereum (Layer 1) and Polygon PoS (sidechain), enabling you to move tokens like ETH, USDC, and other assets between the two networks.
When you bridge assets from Ethereum to Polygon, your tokens are locked in a smart contract on Ethereum, and equivalent tokens are minted on Polygon. When bridging back, the Polygon tokens are burned and the Ethereum tokens are unlocked.
Important: Bridging is different from swapping. You're moving the same asset between networks, not exchanging one token for another.
How the Polygon Bridge Works
Ethereum → Polygon (Deposit)
- 1.You initiate a deposit transaction on Ethereum, sending tokens to the Polygon bridge contract
- 2.Your tokens are locked in the Ethereum bridge contract
- 3.Polygon validators monitor the Ethereum contract and verify your deposit
- 4.Equivalent tokens are minted on Polygon and sent to your address
- 5.Time: 10-20 minutes (waiting for Ethereum block confirmation)
Polygon → Ethereum (Withdrawal)
- 1.You initiate a withdrawal on Polygon, burning your tokens
- 2.Polygon creates a checkpoint (proof of burn) that's submitted to Ethereum
- 3.You wait for the checkpoint to be included on Ethereum (~30 minutes)
- 4.You submit a claim transaction on Ethereum to unlock your tokens
- 5.Total Time: Typically 1–4 hours, depending on checkpoint timing and Ethereum conditions
Bridging Costs
Ethereum → Polygon
You pay Ethereum gas fees to deposit. No Polygon fees.
Polygon → Ethereum
Two transactions required: burn (cheap) + claim (expensive).
What Can You Bridge?
Native Tokens
- ETH - Becomes wrapped as WETH on Polygon
- MATIC - Polygon's native token (both directions)
ERC-20 Tokens
- USDC, USDT, DAI (stablecoins)
- WBTC, LINK, AAVE, UNI
- Most major ERC-20 tokens
NFTs (ERC-721/1155)
- ERC-721 NFTs
- ERC-1155 NFTs
Custom Tokens
- Project-specific tokens (if mapped)
- Requires token mapping submission
Security & Risks
How Secure is the Bridge?
The Polygon bridge is secured by Polygon's validator network and Ethereum smart contracts. Assets locked on Ethereum can only be unlocked through valid proofs submitted from Polygon, and vice versa. The bridge has processed billions in assets since launch.
Known Risks
- Smart Contract Risk: Bridge contracts could have bugs (though heavily audited)
- Validator Dependency: Bridge relies on Polygon validator honesty
- Withdrawal Delays: Polygon to Ethereum takes time for checkpoint submission
Best Practices:
- • Start with small test amounts
- • Verify destination address carefully
- • Keep transaction hashes for tracking
- • Be patient during withdrawals (1–4 hours is normal)
Third-Party Bridge Options
While Polygon's official bridge is the most direct option, several third-party bridges offer different trade-offs:
Faster Withdrawals (Liquidity Bridges)
Services like Hop Protocol and Connext provide near-instant withdrawals by using liquidity pools, avoiding the checkpoint wait time.
Trade-off: Higher fees, liquidity limits, additional smart contract risk
Multi-Chain Aggregators
Platforms like Bungee and Li.Fi aggregate multiple bridges to find the best route and price.
Trade-off: Additional complexity, requires trust in aggregator logic