Topics Blockchain
Bybit Learn
Bybit Learn
Intermediate
22 Th06 2022

How to Bridge Tokens with Polygon Bridge

Ethereum, one of the most popular blockchains, is experiencing significant network congestion, particularly with the introduction of smart contracts that make transactions even more complex. In order to ease this congestion, Ethereum has to raise its gas fees. Polygon Bridge is one of the ways you can get around this obstacle.

Polygon Bridge increases interoperability between the Polygon and Ethereum blockchains. Users can quickly transfer tokens back and forth with a compatible cryptocurrency wallet. It consists primarily of two bridges, the proof of stake (PoS) Bridge and the Plasma Bridge. Each adopts different security methods, but either one can bridge assets from Ethereum to Polygon, and vice versa.

The PoS Bridge uses a proof of stake (PoS) consensus algorithm for network security, and is compatible with most ERC tokens and Ether (ETH). The Plasma Bridge uses the Ethereum Plasma scaling solution and supports the transfer of MATIC, ETH, ERC20, and ERC721 tokens.

In this article, we'll discuss the Polygon Bridge and provide a step-by-step guide to using both the PoS and Plasma bridges.

What Is the Polygon Bridge?

The main issue with Layer 1 blockchains like Ethereum is that they often face congestion issues, due to too many transactions happening in the network at once. This results in slower transaction speeds and higher fees for faster transactions.

Layer 2 blockchains solve this problem by tackling more transactions at lower costs, thus reducing the burden on Layer 1 blockchains.

Polygon is one such Layer 2 blockchain, built on Ethereum, that enables minting of non-fungible tokens (NFTs) and provides faster transactions at lower gas fees. It also helps developers to build and connect DApps in a secure, efficient ecosystem.

Sometimes, we may need our virtual assets transferred from one network to another in order to save gas fees or transaction fees. Polygon Bridge is an Ethereum-compatible bridge that can transfer assets from other blockchains to Ethereum, and vice versa.

Ethereum-based DEXs like QuickSwap and SushiSwap allow you to swap tokens at lower fees. In 2021, AnySwap, a fully distributed protocol for cross-chain token swaps, also created a cross-chain bridge with Polygon. And with Polygon Bridge, you can even transfer both tokens and NFTs across blockchains at a low cost.

How Does Polygon Bridge Work?

Polygon Bridge is a dual-consensus, decentralized system that allows tokens to be transferred across chains. It uses a single token model and supports arbitrary state transitions on sidechains, which are compatible with the Ethereum Virtual Machine (EVM). Cross-chain token transfers can be completed instantly without third-party risks or market liquidity limitations.

Polygon Network unlocks tokens on Ethereum, but the tokens on Polygon are burned after they’ve been bridged back to Ethereum. When bridging tokens across the Polygon Bridge, the circulating supply of the token remains unchanged. Tokens that leave the Ethereum network are locked, and the same number of tokens are then minted on the Polygon Network, pegged on a 1:1 basis.

Polygon has two different bridges for the transfer of assets: Proof of Stake (PoS) Bridge and Plasma Bridge. Each uses a different method to secure networks and complete transactions.

1. PoS (Proof of Stake) Bridge

PoS Bridge Architecture (Formerly Matic Bridge)

Source: Reddit

PoS Bridge (formerly Matic Bridge) uses a PoS consensus to secure its network. While deposits are completed almost instantly, withdrawals may take a while to confirm. The PoS Bridge supports the transfer of Ether (ETH) as well as most ERC tokens.

2. Plasma bridge

Plasma bridge architecture

Source: Polygon Docs

Plasma Bridge uses Ethereum Plasma scaling technology to offer increased transfer security. It supports transfers of Polygon's native token, MATIC, and specific Ethereum tokens, like ETH, ERC20 and ERC721.

How To Use PoS Bridge to Bridge Tokens

To transfer tokens from your wallet to Polygon's, you’ll need:

  • A MetaMask account with some funds in it
  • A Polygon wallet address
  • A Polygon bridge URL

First, make sure you have your seed phrase handy and store it in multiple places so you don't lose it. This is important — because if someone gets their hands on your seed phrase, they can steal all of your funds (thus the expression, “Not your keys, not your funds!”). Once you do this, you can continue the process.

Next, go ahead and visit the Polygon Bridge URL and approve the transaction to log into Polygon’s wallet. Once you're approved, you’ll be able to send tokens from the Ethereum Mainnet to their wallet.

Select which tokens you want to send, click on Transfer, and wait about 7 to 8 minutes for them to deposit into your MetaMask wallet. Polygon Bridge should show a progress bar indicating when your transfer is complete.

Let's look at some detailed steps for using PoS to bridge tokens from the Ethereum network to Polygon Network, and vice versa.

From Ethereum to Polygon

If you're new to Polygon, you may be wondering how to bridge tokens from Ethereum to Polygon Network. It's a simple process that takes just a few minutes.

  1. To connect, first log in to Polygon Web Wallet, then select the wallet you wish to connect to.
  2. From Ethereum to Polygon Step 1: Connect MetaMask wallet to Polygon

    Source: Wallet.polygon.technology

  3. Click on Sign under [Signature Request]. You will then be redirected to the Polygon Bridge portal.
  4. From Ethereum to Polygon Step 2: Sign message to log in

    Source: Wallet.polygon.technology

  5. To send your tokens from the Ethereum Mainnet to Polygon Network, find the Deposit tab, and then click on the token name (for example, Ether). Enter the number of tokens you want to deposit into your Polygon Network account, and then click on Transfer.
  6. From Ethereum to Polygon Step 3: Click Transfer on Deposit Tab

    Source: Wallet.polygon.technology

  7. Read the Important pop-up message and click on Continue.
  8. From Ethereum to Polygon Step 4: Read Important message and click Continue

    Source: Wallet.polygon.technology

  9. The estimated gas fee required for the transaction will be shown in the Transfer Overview pop-up. If you’re okay with the amount, click on Continue to proceed.
  10. From Ethereum to Polygon Step 5: Click on Continue in Transfer Overview

    Source: Wallet.polygon.technology

  11. Check the transaction details and gas fee of the transaction before clicking on Continue.
  12. From Ethereum to Polygon Step 6: Check details and click Continue.

    Source: Wallet.polygon.technology

  13. Approve the token transfer in your MetaMask wallet. If the details are correct, click on Confirm.
  14. From Ethereum to Polygon Step 7: Check details and click Confirm.

    Source: Wallet.polygon.technology

  15. Wait for the tokens to be transferred to your wallet. Then, click on View on Etherscan to check the status of the transaction.
  16. From Ethereum to Polygon Step 3: Click View on Etherscan

    Source: Wallet.polygon.technology

Note that validators secure the PoS Bridge. In the event that you want to move funds back to Ethereum, it may take around one to three hours.

From Polygon to Ethereum

You can use Polygon Bridge to transfer tokens from Polygon Network to Ethereum or other compatible crypto wallets, such as MetaMask.

Each Polygon Bridge has different withdrawal times. While the PoS Bridge withdrawal may range from one to three hours, the Plasma Bridge withdrawal can take up to seven days.

Transferring tokens from Polygon to Ethereum is simple!

  1. If you want to transfer some of your tokens from the Bridge platform to another wallet, you can click on Withdraw on the Bridge interface. Choose the tokens you wish to move, and click on Transfer.
  2. The (Switch Bridge) button next to Transfer Mode will help you pick a compatible bridge for your chosen token. Once you've selected the token, enter the amount you want to send and click on Transfer.
  3. rom Polygon to Ethereum Step 2:  Click Transfer on Withdraw tab

    Source: Wallet.polygon.technology

  4. Read the Important pop-up message before proceeding. You'll also see an estimated gas fee for this transaction. If the fee is acceptable to you, click on Continue to go forward with your withdrawal.
  5. You can review your transaction details before signing off on it in your MetaMask wallet. Make sure everything is in order, then click on Continue. Your withdrawal will begin on the network.
  6. Next, you’ll see the transfer progress bar loading until it completes. The withdrawal process will be kicked off, and the transactions will be verified by PoS validators, which may take up to three hours.
  7. From Polygon to Ethereum Step 5: Transfer in progress – Waiting for Checkpoint

    Source: Wallet.polygon.technology

  8. Once your transaction is validated, you must claim the tokens to your MetaMask wallet. Click on Continue and your assets will be transferred to the MetaMask wallet once the transfer is complete.
From Polygon to Ethereum Step 6: Transfer in progress – Checkpoint arrived, click Continue

Source: Wallet.polygon.technology

How to Use Plasma Bridge to Bridge Tokens

You can use Plasma Bridge in order to exchange MATIC and other Polygon tokens for Ethereum. Plasma Bridge only supports the transfer of ERC20 and ERC721 tokens, including ETH and MATIC.

The MetaMask wallet is connected to Ethereum by default. To connect MetaMask and Polygon Network, you’ll first need to add Polygon to MetaMask. There are two ways to do so, either manually or through the Polygon Wallet interface. Only after adding Polygon to MetaMask will you be able to proceed with using Plasma Bridge.

Bridging From Plasma Bridge To Ethereum

  1. To make the cross-bridge transfer, you’ll need to head to the Bridge interface and click on Withdraw. Choose the MATIC token, enter your desired amount, and click on Transfer.
  2. Plasma Bridge Step 1: Click Transfer on Withdraw tab

    Source: Wallet.polygon.technology

  3. The Important notification will appear. Read it, and click on Continue to proceed.
  4. A gas fee estimate will also be shown. You can continue if you’re okay with the gas fee.
  5. Make sure the details of your transaction are accurate before before clicking on Continue.
  6. Plasma Bridge Step 4: Check details and click Continue.

    Source: Wallet.polygon.technology

  7. The MetaMask confirmation pop-up will appear. Click on Confirm. You’ll see the transfer progress bar start to load. You’ll need to wait three hours for it to reach Checkpoint.
  8. Plasma Bridge Step 5: Transfer in progress – Waiting for Checkpoint

    Source: Wallet.polygon.technology

  9. Next, you’ll notice that it’s slightly different from the PoS Bridge transfer in that it needs a second confirmation from you after the Checkpoint arrives. This will set the Challenge Period in motion. 
  10. Plasma Bridge Step 5: Transfer in progress – Checkpoint arrived

    Source: Wallet.polygon.technology

  11. After the Challenge Period is complete, click on Continue to send the tokens to your MetaMask wallet.
  12. Plasma Bridge Step 7: Challenge period completed – Click Continue

    Source: Wallet.polygon.technology

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Final Thoughts

Most popular platforms are cluttered with several tokens, leading to network congestion, slower transaction times and high gas fees.

Polygon Network has targeted this issue, and has entered the market when popular platforms are highly cluttered. Polygon Bridge is an excellent enabler of interoperability between blockchain networks. It also reduces carbon emissions — and offers lower gas fees and faster transactions on the Polygon Network blockchain.