You’ve done a few swaps on Ethereum mainnet. You know your way around MetaMask. And then you try to make a $100 trade and the gas fee comes back at $38. Learning how to bridge to L2 is how you stop paying those fees permanently — and keep doing everything you’re already doing on DeFi, just for pennies instead of dollars.
Layer 2 networks like Arbitrum and Base run on top of Ethereum, inherit the same security, and let you execute the same transactions for $0.01 to $0.50 each. The same protocols you’ve been using on mainnet — Uniswap, Aave, Curve — are fully deployed on Arbitrum. You bridge your ETH over once, and then you can trade, swap, and manage positions without checking whether the gas fee wipes out your profit.
This post walks you through exactly how to do it, safely.
Why Mainnet Gas Makes DeFi Painful (and Why L2 Fixes It)
Ethereum mainnet gas fees are priced by network demand. When traffic is high — and it’s almost always high — fees spike. A simple token swap costs $5 on a slow day and $50+ when the market is moving. Providing liquidity, adjusting positions, and claiming rewards all add up fast.
Layer 2 networks solve this by processing transactions in batches off the main chain, then posting compressed proofs back to Ethereum for security. The result:
- Ethereum mainnet: $5–$50+ per transaction
- Arbitrum: $0.01–$0.25 per transaction
- Base: $0.01–$0.50 per transaction
That’s a 100x to 500x cost reduction on the same activity. If you’re making 10 DeFi moves a month and spending $20 average in gas, that’s $200/month just to interact with protocols. The same 10 transactions on Arbitrum cost under $3.
Two L2s worth starting with:
- Arbitrum — the largest L2 by Total Value Locked (TVL, meaning the total assets deposited in its protocols). It has a complete DeFi ecosystem: Uniswap V3, Aave, Curve, GMX, Camelot, and dozens more. If you’ve used any of these on mainnet, they work identically on Arbitrum.
- Base — Coinbase’s L2. Newer, growing fast, and has a significant onboarding advantage: if your ETH is sitting on Coinbase exchange, you can send it directly to Base without touching a bridge at all.
For a deeper explanation of why L2 networks exist and how they secure their transactions, see our Ethereum Layer 2 Explained overview.
How Bridging Works (The Concept)
Bridging sounds technical. It’s actually a straightforward two-step lock-and-mint process.
When you bridge ETH from Ethereum mainnet to Arbitrum:
- Your ETH is locked in a smart contract on mainnet
- An equivalent amount of ETH appears in your wallet on Arbitrum (same address, different network)
To bridge back, the process reverses: your Arbitrum ETH is burned, and the original ETH on mainnet is released back to you.
Official bridges vs. third-party bridges: Official bridges (bridge.arbitrum.io and bridge.base.org) are operated by the L2 teams themselves — the most trustworthy option. The downside: deposits take 15–20 minutes, and withdrawals back to mainnet take 7 days (this is a security feature called the “challenge period,” not a bug).
Third-party bridges like Across Protocol use liquidity pools on both ends to speed things up to 1–3 minutes, with a small fee (0.1–0.3%). Once you’ve done a bridge or two and feel comfortable, these are worth using. For your first bridge, stick to the official bridge.
Step-by-Step: Bridge to Arbitrum
Here’s the full process using the official Arbitrum bridge.
What you need before you start:
- MetaMask with ETH on mainnet
- At least $50–$100 to bridge (small enough to be a test, large enough to be meaningful)
- A few extra dollars of ETH on mainnet to pay the bridge gas fee (~$3–$8)
Steps:
- Open a browser and type bridge.arbitrum.io directly — do not click links from Twitter, Discord, or search ads
- Click “Connect Wallet” and connect MetaMask
- Confirm the “From” chain shows Ethereum and “To” shows Arbitrum One
- Enter the amount you want to bridge ($50–$100 recommended for your first time)
- Click “Move funds to Arbitrum One”
- MetaMask will ask you to confirm a mainnet transaction — this is the one-time bridge gas fee
- Wait 15–20 minutes
- MetaMask may prompt you to add the Arbitrum One network — accept it
- Switch to the Arbitrum One network in MetaMask and verify your ETH balance
Done. Your ETH is now on Arbitrum. Every transaction from here costs a few cents.
Step-by-Step: Bridge to Base
Base follows the same process as Arbitrum.
- Go to bridge.base.org directly (type it, don’t click a link)
- Connect MetaMask
- Select amount and bridge from Ethereum to Base
- Confirm and wait (~15 minutes)
Coinbase shortcut: If your ETH is sitting in a Coinbase exchange account (not MetaMask), you can skip the bridge entirely. From Coinbase, go to Send → paste your MetaMask wallet address → select Base network as the destination. Your ETH arrives in minutes with no bridge required. This is the fastest path onto Base if you’re already a Coinbase user.
Using a Fast Bridge: Across Protocol
If the 15–20 minute wait on official bridges doesn’t work for you, Across Protocol is the most established fast bridge. It connects Ethereum, Arbitrum, Base, Optimism, and other networks and typically settles in 1–3 minutes.
- Go to app.across.to (type directly)
- Connect your wallet
- Select source chain (Ethereum) and destination (Arbitrum or Base)
- Enter your amount
- Review the fee — typically 0.1–0.3% of the amount being bridged
- Confirm and wait a few minutes
Across has been audited multiple times and has processed billions in bridge volume. Other well-audited fast bridges include Stargate and Hop Protocol. These are reasonable options. A bridge you found via a random Twitter link is not.
Bridge Safety Rules You Should Not Skip
Bridging is one of the higher-risk DeFi actions — not because the technology is dangerous, but because phishing sites target bridge users specifically. The most common attack: a fake bridge site that looks identical to the real one, which drains your wallet the moment you connect.
What to do:
- Always type bridge URLs directly into your browser: bridge.arbitrum.io, bridge.base.org, app.across.to
- Bookmark these URLs after your first visit and use the bookmarks going forward
- Bridge a small test amount first before moving larger sums
- Double-check that MetaMask shows the correct destination network before you confirm
What not to do:
- Never click bridge links from Twitter, Telegram, or Discord — these are the most common source of phishing attacks
- Never use a bridge found through a Google ad
- Never use a bridge recommended in a random Discord server, even a popular one
One more thing: bridging to L2 is straightforward, but bridging to the wrong address or wrong network can be difficult or impossible to recover. Take 30 seconds to verify the destination before confirming.
What to Do Once You’re on L2
Once your ETH is on Arbitrum or Base, DeFi works exactly the same — just cheaper.
Swapping on Uniswap (Arbitrum):
- Go to app.uniswap.org
- Click the network selector (top right) and choose “Arbitrum”
- Swap tokens exactly as you would on mainnet — using a DEX aggregator still applies here for better prices on larger amounts
- Gas will be a few cents
Using Aave on Arbitrum:
- Go to app.aave.com
- Select “Arbitrum” in the network dropdown
- Deposit, borrow, and manage collateral positions at a fraction of mainnet cost
Keep a small ETH reserve: Gas on L2 is paid in ETH, just in tiny amounts. Keep at least 0.01 ETH in your L2 wallet as a gas buffer. If you run out, you can’t send anything — including bridging back to mainnet.
The Bottom Line
High mainnet gas fees are a solved problem. Layer 2 networks give you access to the same DeFi protocols, backed by the same Ethereum security, at 100x lower cost. The bridge is a one-time learning curve — 20 minutes of setup that pays for itself the first time you execute a trade for $0.08 instead of $40.
Bridge a small amount. Get comfortable with the new network. Then move the rest and stop paying mainnet tax on every transaction.
Ready to build your DeFi skills step by step? Follow the 90-Day Wallet Security Progression — a structured path from first wallet to confident DeFi user, in the right order. Each step builds on the last so you’re never left guessing what to learn next.