How to Add BTC to MetaMask: An Advanced Guide

Introduction: Bridging Bitcoin and Ethereum

MetaMask has emerged as one of the most popular ways to interact with decentralized applications built on Ethereum and other EVM-compatible networks. With over 30 million monthly users as of 2022, its browser extension makes Web3 feel accessible for mainstream audiences.

Bitcoin, despite its market dominance, has remained more siloed from broader crypto innovation like DeFi and NFTs happening in Ethereum‘s ecosystem.

Bridging these two worlds to unlock Bitcoin‘s functionality for Ethereum users has seen rising interest. According to Dune Analytics, over 250,000 BTC representing $5.2 billion in value has now been bridged to the Ethereum network through wrapping protocols as of September 2022.

{{Image: BTC Bridged to Ethereum.png}}

This guide will equip you to access your Bitcoin seamlessly within MetaMask through technical methods like token wrapping and blockchain bridges. You‘ll also gain deeper perspective into the design tradeoffs around decentralization and convenience when bridging between the maximalist security of Bitcoin and the permissionless innovation of Ethereum.

Let‘s dive in!

Setting Up MetaMask

Before bridging Bitcoin over, you‘ll first need to install and configure MetaMask correctly:

Step 1: Download and Setup

MetaMask.io

• Browser Extension: Chrome, Brave, Firefox
• Mobile: iOS and Android apps

Follow the prompts when first opening MetaMask to create a new wallet. This generates your:

• Seed Phrase (backup this!)
• Password
• Public Address on Ethereum networks

Your seed phrase restores the entire wallet if you ever lose access. The password encrypts sensitive activity like sending transactions. The public address is what others send funds to, like an account number.

Step 2: Connect to Ethereum Mainnet

By default, MetaMask adds the Ethereum Mainnet ensuring compatibility with all ERC20 tokens and Ethereum-based DeFi apps.

You can see what network you‘re connected to in the top right dropdown menu:

{{Image: Network dropdown.png}}

Other common networks like Polygon and Binance Smart Chain can be added later under Settings > Networks > Add Network to leverage faster/cheaper DeFi options.

For this BTC guide, Ethereum mainnet is essential given most wrapped Bitcoin protocols issue tokens there. We‘ll revisit integrating other chains that unlock more advanced functionality later on.

Step 3: Fund with ETH for Gas Fees

You‘ll need a small amount of ETH in your MetaMask wallet to pay gas fees for activities like sending transactions and interacting with dApps built on Ethereum.

Think of gas like fuel for powering execution of smart contracts. More complex logic costs more gas. You choose the gas price (in GWEI) when transacting, with priority based on who pays more.

Now that MetaMask is set up and connected to Ethereum mainnet, let‘s explore different methods for adding BTC…

Method 1: Wrap using WBTC

The most straightforward approach is converting your BTC 1:1 into an ERC20 equivalent known as wBTC (Wrapped Bitcoin). Here‘s an overview:

• BTC is sent to certified "merchants" like BitGo.
• These merchants run nodes that confirm BTC‘s locked up via proof-of-reserves.
• Smart contracts mint wBTC tokens on Ethereum in a 1:1 ratio.
• wBTC is burned when users want to unlock back to regular BTC.

This framework of custodians and issuing contracts allows Bitcoin to have mirrored ERC20 representation for DeFi activity while ensuring full 1:1 backing.

Adopting Wrapped Bitcoin (WBTC)

{{Image: WBTC Supply Growth.png}}

wBTC saw gradual growth since launch in 2019, but hit an inflection point in 2022 – rising 500% from 80,000 BTC wrapped to over 500,000 BTC today valued around $10 billion. WBTC now boasts the 3rd largest market cap of any ERC20 asset.

This validates a clear appetite for accessing Bitcoin‘s store-of-value and brand within Ethereum‘s existing financial ecosystem.

Here are step-by-step instructions for wrapping via WBTC protocol:

1. Send BTC to an Authorized Merchant

Certified merchants are whitelisted by the WBTC DAO as trusted to custody backing BTC. Leading options:

• BitGo: Institutions/OTC Desks
• Kyber Network: Retail Users
• CoinList: Retail/Institutions

We‘ll use Kyber as an example. Head to their WBTC Portal and connect your Ethereum wallet.

Make sure you have enough BTC in the connected Bitcoin wallet to wrap.

2. Initiate the Minting Process

Choose the amount of WBTC you want minted, and approve a small ETH fee for the on-chain transaction. Kyber requests the BTC to lock up from your connected BTC wallet.

3. Wait for Confirmations

It takes roughly 60 min for the merchant to receive, verify via 6 blockchain confirmations, and signal the smart contract to mint WBTC. Speed depends on Bitcoin network congestion.

The ERC20 WBTC is minted directly to your Ethereum (MetaMask) public address once complete!

Now let‘s walk through adding this wrapped token to MetaMask.

4. Add WBTC Custom Token in MetaMask

Open MetaMask browser extension and click "Add Token":

{{Image: Add token MetaMask.png}}

Select "Custom Token" and input:

• Contract Address: 0x2260fac5e5542a773aa44fbcfedf7c193bc2c599
• Token Symbol: WBTC
• Decimals: 8

Click "Next" then "Add Token" – WBTC balance now tracks directly in MetaMask!

{{Video: Adding WBTC to Metamask.mp4}}

You can now transact WBTC just like any ERC20! But remember, unwrap back to BTC by burning requires similar bridging steps.

Other Wrapped Bitcoin Protocols

Projects like renBTC (renBridge) and tBTC (Keep Network) offer similar BTC wrapping models with different decentralization tradeoffs:

While wBTC saw first mover advantage, alternative wrap protocols aim for reduced counterparty risk and permissionlessness via innovative models like RenVM and tBTC‘s bonding model requiring collateral from wrapping providers.

Understanding these nuances allows picking the right solution for your needs across custody, decentralization and accessibility.

Now let‘s examine even more seamless bridging methods…

Method 2: Leveraging Blockchain Bridges

Beyond wrapping BTC to an ERC20 twin, blockchain bridges allow swapping Bitcoin directly to other blockchain networks compatible with MetaMask like Polygon and Binance Smart Chain (BSC).

Bridges federate transactions across chains – opening up faster/cheaper transactions with EVM compatibility for DeFi. Leading options include Connext, Synapse and IBC based networks.

Let‘s walk through bridging Bitcoin to Polygon PoS within MetaMask using the popular Synapse Protocol…

1. Fund MetaMask on Polygon

Ensure MetaMask is connected to Polygon Mainnet. Add network if needed:

Network Name: Polygon Mainnet
RPC URL: https://polygon-rpc.com
Chain ID: 137

Have a small amount of MATIC coins available to pay gas for bridging.

2. Head to Synapse Bridge

Select Bitcoin as input currency, and MATIC token on Polygon network as the output.

3. Initiate Bridge Transfer

Connect your BTC wallet (can be exchange account even) and specify receive address. Includes ETH gas estimate for synapse transaction.

Approve to trigger Bitcoin transfer. Takes ~60 minutes for Synapse validators to process and mint MATIC token on Polygon.

4. MATIC Tokens Bridged to MetaMask

With the Polygon network added already, your new MATIC tokens will show automatically in MetaMask once received!

You can now leverage Polygon‘s near instant settlement and fractions of a penny fees to use this bridged Bitcoin within DeFi apps. No need to wrap tokens manually.

Evaluating Bitcoin Bridge Services

Here we compare some leading blockchain bridge designs across security models and decentralization. Hash timelocks utilize time-based enforcement, while IBC enables interoperability between Cosmos SDK cryptocurrencies

Understanding subtle technical and governance differences allows better evaluation based on your priorities – convenience, decentralization, flexibility across multiple chains.

Now let‘s explore solutions that unlock Bitcoin directly within MetaMask…

Method 3: Native Integration via Proxy Contracts

Thus far we examined token wrapping solutions like wBTC mimicking Bitcoin‘s value in ERC20 tokens and blockchain bridges that swap to intermediate "pegged" assets.

Innovations in smart contract design now allow trustlessly mirroring Bitcoin‘s balance and UTXOs directly using proxy contracts built natively on networks like Polygon and Gnosis Chain.

This means your Bitcoin is accessible on both blockchains concurrently without conversions, facilitating zero slippage sending/receiving across chains.

Here‘s how it works…

Proxy Contract Mechanics

Standard proxy contracts act as accessible mirrors tracking BTC holdings, balances and transaction data through heads that validate Bitcoin‘s state:

{{Image: Proxy contract network.png}}

Light clients like Electrs quickly scan and filter the Bitcoin blockchain, relaying simplified cryptographic proofs to contracts verifying UTXO positions and balances rather than entire history.

This enables wallets like MetaMask to display real-time mainnet BTC balances without custody through an architecture purpose built for EVM compatibility.

Leading proxy contract implementations include:

• Polygon (PoS) – Native BTC along with ZEC, XRP, LTC and more
• Gnosis Chain (formerly xDai) – bzX modules for BTC, ETH and stablecoins

Let‘s walk through adding Bitcoin RPC to MetaMask on Polygon PoS…

1. Add Polygon PoS Custom Network

In MetaMask extension click networks dropdown > add network:

Network Name: Polygon Mainnet

New RPC URL:
https://polygon-rpc.com/

Chain ID: 137

Currency Symbol: MATIC

2. Import the Polygon BTC token

Navigate add token > custom token and input contract address:

Address: 0x1bfd67037b42cf73acf2047067bd4f2c47d9bfd6

Token Symbol: BTC and Decimals 8 auto-populates. Click add!

Your actual BTC balance now shows in MetaMask wallet via Polygon PoS!

{{Video: Adding Polygon BTC to MetaMask.mp4}}

You can send, receive, lend, borrow even leverage trade using UX tuned DeFi platforms – benefiting from Bitcoin‘s unparalleled liquidity and brand with the accessibility and scalability of Ethereum L2 solutions.

This bi-directional transferability between Bitcoin and EVM chains unlocks self-custody advantages Bitcoins holders value while connecting to innovative DeFi protocols like Aave, Curve and Balancer all accessible directly in your MetaMask wallet.

Key Takeaways: Bridging Bitcoin to MetaMask and Beyond

Wrapped tokens, blockchain bridges and native proxy contracts each provide compelling methods for surfacing Bitcoin balances within MetaMask to engage with Ethereum‘s broad decentralized application ecosystem.

While conceptually straightforward, understanding nuances around decentralization tradeoffs, transaction finality, network effects and fees enable sound evaluation.

Here are some closing remarks looking towards the multi-chain future:

• Simplicity vs. Decentralization – Solutions emphasizing convenience tend towards efficiency over permissionlessness. Evaluate your priorities around custody requirements.
• Dynamic Bridging – Bidrectional transferability provides advantages over one-way pegging, albeit with more protocol complexity.
• Atomic Transaction – IBC, Connext and others enable "atomically" swapping assets cross-chain without counterparty risk. This overcomes current limitations.
• Light Clients – Proxy contracts rely on light client relayers indexing data. This can introduce liveness assumptions.
• EVM Constantinople – Updates allowing EVM compatibility for wrapping Bitcoin natively could prompt migration from legacy bridges.

As MetaMask continues push the boundaries of usability for non-custodial wallets, seamless Bitcoin integration via leading cross-chain bridging protocols expands access and utility for decentralized finance.