Compound Protocol - Lend & Borrow in DeFi

Introduction

Compound Protocol, launched in 2018 by Robert Leshner, pioneered the algorithmic money market model that most DeFi lending protocols now follow. With Compound V3 (Comet), the protocol shifted from pooled multi-asset markets to single-borrowable-asset markets -- each Comet instance lets you borrow one asset (e.g. USDC) against multiple collateral types. This architecture simplifies risk modelling, eliminates cross-asset contagion, and has kept Compound amongst the top five lending protocols by TVL.

This guide covers how Compound actually works in 2026, including current supply and borrow rates, the V3 Comet architecture, COMP governance, and honest limitations you should weigh before depositing. Compare DeFi lending platforms or read our DeFi guide.

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What Is Compound Protocol?

Compound is a decentralised lending protocol on Ethereum where you supply crypto to earn interest or borrow against collateral -- all governed by smart contracts with no intermediaries. Interest accrues every block (~12 seconds), so even a single day of supply generates measurable yield. At its peak it held over $3 billion in TVL (DeFiLlama).

Current Market Snapshot (2026)

• TVL: $800M-$1.2B across all Comet markets
• Largest market: USDC Comet ($400M+ supplied)
• USDC supply APY: ~3-4%; borrow APY: ~5-6%
• ETH supply APY: ~0.5-2%; borrow APY: ~1-4%
• Collateral assets: ETH, WBTC, wstETH, cbETH, COMP, UNI, LINK
• Risk modelling: managed by Gauntlet and Chaos Labs (collateral factor tuning, liquidation parameters)

V3 Comet Architecture

Compound V3 replaced the original multi-asset pool model with isolated Comet markets. Each Comet instance has exactly one borrowable asset (e.g. USDC or ETH) and accepts multiple collateral types. This design means a problem in one collateral asset cannot cascade into other borrowing markets -- a direct response to the risk management lessons of 2022. You no longer receive cTokens; instead, your supplied base asset earns interest directly in your Comet balance.

In Compound V2, every supplied asset generated a corresponding cToken (cUSDC, cETH, cDAI) that represented your deposit plus accrued interest. The cToken balance grew over time as the exchange rate increased. This was composable -- you could deposit cTokens into other DeFi protocols as collateral -- but it also spread risk across a single shared pool. If one asset in the pool suffered a bad debt event, all suppliers shared the loss. V3's Comet model eliminates this by separating collateral assets (which earn no interest) from the base asset (which earns interest when supplied). Collateral is locked and cannot be borrowed by other users -- it exists solely to back your debt. This makes the risk boundary explicit: a sharp drop in WBTC price affects only WBTC collateral positions, not USDC suppliers.

COMP token holders govern the protocol through on-chain proposals -- adjusting collateral factors, adding markets, and tuning interest rate curves. Over 200 governance proposals have been executed since launch. However, governance power is concentrated: a handful of large delegates control a majority of voting weight, which is worth considering if decentralisation matters to you.

Key Features of Compound Protocol

Lending (V3 Comet)

• Supply base assets: Deposit USDC or ETH into a Comet market and earn interest immediately. No lock-up period, no minimum deposit
• Algorithmic rates: Supply APY adjusts every block based on utilisation. USDC currently earns ~3-4% base APY
• No cTokens in V3: Your balance accrues interest directly in the Comet contract. Simpler than the V2 cToken model

Borrowing (V3 Comet)

• Single-asset borrowing: Each Comet lets you borrow one asset (e.g. USDC) against multiple collateral types (ETH, WBTC, wstETH, cbETH, COMP, UNI, LINK)
• No fixed terms: Borrow indefinitely with no repayment schedule. Interest accrues per block
• Collateral factors: Borrow up to 75-83% of collateral value depending on asset risk tier. ETH has the highest factor

COMP Governance Token

• COMP rewards: Distributed to suppliers and borrowers, though reward rates have decreased significantly since 2021
• Governance voting: COMP holders vote on protocol changes. Creating proposals requires 25,000 COMP (~$1M+)
• Concentration issue: A small number of delegates (notably a16z, Polychain, Gauntlet) control a majority of voting power. Protocol changes largely reflect institutional preferences
• Delegation: You can delegate your voting power if you hold COMP but do not want to vote on every proposal

COMP's governance model uses a two-stage process: a proposal is submitted on-chain, undergoes a 3-day open voting period, and if passed is queued in the 48-hour timelock before execution. The timelock is a meaningful user protection -- if a governance proposal would change collateral factors or freeze withdrawals in a way that harms you, you have 48 hours to exit after the vote passes. This window is shorter than Aave's 72-hour timelock but longer than many smaller protocols. The 25,000 COMP threshold for proposal creation (worth roughly $700,000-$1,000,000 at typical 2026 prices) means grassroots governance proposals are rare; in practice, most proposals originate from Gauntlet, Chaos Labs, or large institutional delegates who regularly engage with the protocol.

How to Get Started with Compound

Step 1: Wallet and Gas

You need a Web3 wallet (MetaMask, Coinbase Wallet, or hardware wallet via WalletConnect) and ETH for gas. Typical gas costs on Ethereum mainnet: $10-30 per supply/withdraw, $15-40 per borrow/repay. If gas costs eat too much of your position, wait for low-congestion periods or consider Compound on Base/Arbitrum where fees are under $1.

Step 2: Connect and Supply

Visit compound.finance, connect your wallet, and select a Comet market (USDC Comet is the largest). Approve the token (one-time gas cost), then supply your amount. Interest starts accruing immediately with no lock-up.

Step 3: Monitor Your Position

Track your position with Zapper, DeBank, or the Compound dashboard directly. If you are borrowing, watch your collateral ratio closely -- if it drops below the liquidation threshold, your collateral will be sold at a discount. Keep your ratio above 200% for safety margin during normal conditions, and consider 250%+ during volatile market periods when ETH can drop 15-20% in a single day.

Gas Optimisation Tips

Ethereum mainnet gas fees significantly affect your returns on Compound, particularly for smaller positions. A supply transaction typically costs $10-30 during normal congestion, meaning a $1,000 position earning 3% APY would spend roughly a full month's yield on the initial deposit gas alone. To minimise costs, transact during weekend mornings (UTC) when gas prices regularly drop to 5-15 gwei, or consider using Compound on Base or Arbitrum where the same operations cost under $1.

For larger positions ($10,000+), gas costs become proportionally insignificant. However, you should still be mindful of frequent claim or rebalance transactions. If you plan to supply and leave your position untouched for months, a single supply transaction on mainnet is perfectly cost-effective. For active strategies involving regular collateral adjustments, Layer 2 deployments offer substantially better economics.

Pros & Cons of Compound Protocol

Advantages

• Proven since 2018: No major exploits on the core protocol. Audited by Trail of Bits, OpenZeppelin, and formally verified
• No lock-ups: Withdraw supplied assets instantly at any time
• Isolated risk (V3): Comet architecture means a problem in one collateral type cannot cascade to other markets
• No KYC: Anyone with a Web3 wallet can supply or borrow. No identity verification
• Full transparency: Every rate change, liquidation, and governance vote is publicly verifiable on-chain

Disadvantages

• Ethereum gas costs: A single supply transaction costs $10-30. Positions under $5,000 lose a meaningful percentage of APY to gas alone
• Fewer markets than Aave: Under 10 collateral types per Comet vs Aave's 100+ assets across 7+ networks
• Lower supply rates: V3's conservative design means rates typically run 0.5-1% below Aave for equivalent assets
• Governance concentration: ~10 delegates control most voting power. Small holders have negligible influence
• No flash loans: Unlike Aave, Compound does not offer single-transaction uncollateralised borrowing
• No stable rate option: All borrowing uses variable rates that can spike during high utilisation
• Smart contract risk: Despite audits, DeFi smart contracts can never be considered 100% safe

Current Interest Rates & Yields

Rates are algorithmic and change every Ethereum block (~12 seconds) based on market utilisation. These ranges reflect typical 2026 conditions and can shift materially during high-demand periods:

Supply APY (What You Earn)

• USDC: 3-4% base + modest COMP rewards
• ETH: 0.5-2% base. Lower because ETH borrowing demand is smaller
• WBTC: 0.2-1% base. Minimal demand

Borrow APY (What You Pay)

• USDC: 5-6% in normal conditions. Can spike above 20% during high utilisation events
• ETH: 1-4%. Cheaper to borrow because of lower demand

COMP Rewards

COMP distribution has decreased significantly since the protocol's early days. In 2020-2021, COMP rewards could add 5-10% APY on top of base rates, making Compound one of the most attractive yield sources in DeFi. By 2026, COMP rewards contribute less than 0.5% additional APY for most markets. Do not factor COMP rewards into your yield calculations as the primary reason to use Compound -- the base APY should justify the position on its own. COMP rewards are a bonus, not a strategy. Rewards are claimable at any time via the Compound interface or directly through the Comet contract's claim() function; unclaimed rewards do not expire but each claim incurs a gas cost, so it is worth batching claims on mainnet to once a month or more, or claiming freely on Base where gas is negligible.

Security & Risk Management

Protocol Security

• Audits: Trail of Bits, OpenZeppelin, and formal verification of core contracts
• Bug bounty: Up to $500,000 for critical vulnerabilities
• Timelock: 48-hour delay on all governance-executed changes, giving users time to exit before parameter changes take effect
• Risk modelling: Gauntlet and Chaos Labs continuously simulate collateral factor adjustments and liquidation scenarios

Your Risk as a User

• Liquidation: If your collateral value drops below the threshold (e.g. 83% for ETH), your position gets absorbed and sold at a 5-10% discount. Keep ratios above 200% for safety
• Rate spikes: If utilisation jumps above the kink (80-85%), borrow rates spike sharply. A $100K USDC borrow could go from 5% to 50% APY during a liquidity crunch
• Smart contract risk: Despite audits, no DeFi protocol is immune. Never deposit more than you can afford to lose
• Use a hardware wallet: Connect Ledger or Trezor via MetaMask for any position above $10K

Advanced Strategies on Compound

Leveraged Staking

Supply wstETH as collateral in the ETH Comet, borrow ETH, stake the borrowed ETH for more wstETH, and repeat. This amplifies your staking yield but also amplifies liquidation risk if the wstETH/ETH peg breaks. Only viable when the staking yield exceeds the borrow rate.

Rate Arbitrage

When Compound's USDC supply rate exceeds Aave's borrow rate (or vice versa), you can earn the spread by supplying on one and borrowing on the other. The spread is typically small (0.5-1%) and gas costs eat into profits, so this only works with large positions ($100K+).

Automated Position Management

DeFi Saver can automatically repay or add collateral to your Compound position if your health factor drops below a threshold. This prevents liquidation during flash crashes. Setup costs gas but saves you from monitoring positions 24/7.

Technical Architecture

Interest Rate Model (Kinked Curve)

Each Comet market uses a kinked interest rate curve with a target utilisation (typically 80-85%). Below the kink, rates rise gradually -- e.g. USDC borrow rates might go from 2% to 5% as utilisation climbs from 0% to 80%. Above the kink, rates spike sharply (the "jump multiplier"), sometimes reaching 50%+ APY, which incentivises rapid repayment and fresh supply. You can predict rate movements by watching utilisation on-chain -- if a market sits at 82% utilisation, borrow rates are already elevated and likely to rise further.

The interest rate model is encoded directly in the Comet contract as two separate linear segments joined at the kink. The governance-set parameters are: supplyKink, supplyPerYearInterestRateBase, supplyPerYearInterestRateSlopeLow, and supplyPerYearInterestRateSlopeHigh. Supply and borrow rate curves are set independently, so the spread (borrow rate minus supply rate) is always positive -- this spread funds the reserve factor. Because rates update every block, there is no concept of a settlement period; the rate you pay on a borrow changes continuously with market conditions. For time-sensitive strategies, check utilisation immediately before transacting rather than relying on rates you saw an hour earlier.

Liquidation Mechanics

When a borrower's collateral value drops below the liquidation threshold (e.g. 83% for ETH collateral in the USDC Comet), any address can liquidate the position. The liquidator repays part of the debt and receives collateral at a discount (typically 5-10%). Compound V3 uses an absorption mechanism where the protocol itself absorbs undercollateralised positions and sells collateral through a Dutch auction, reducing MEV extraction compared to V2's first-come liquidation model.

The Compound V3 absorption process works in two steps. First, any address calls absorb() on the Comet contract. The protocol takes ownership of the borrower's collateral and wipes the bad debt from its books, paying the caller a small absorb incentive in COMP. Second, the collateral sits in the Comet contract and is auctioned off via buyCollateral() -- the price starts above market and decreases over time until a buyer steps in. This Dutch auction structure is more predictable than V2's race condition, where searcher bots competed to front-run each other in the same block. For borrowers, the practical implication is straightforward: if your position is absorbed, you lose the collateral but your debt is cancelled. You will not owe anything beyond the absorbed collateral -- there is no deficit that follows you.

Each collateral asset has two separate thresholds: the collateral factor (the maximum LTV at which you can borrow) and the liquidation factor (the point at which absorption triggers). For ETH in the USDC Comet, the collateral factor is typically 83% and the liquidation factor 90%. This 7-percentage-point gap means your position can move from maximum borrow capacity to liquidation threshold during a roughly 8% adverse price move. During the 2022 bear market, ETH dropped over 30% in a single week -- positions close to maximum borrow would have been absorbed multiple times over.

Reserve Factor

A percentage of interest payments (the reserve factor, typically 5-20%) flows to the protocol's reserves rather than to suppliers. These reserves act as an insurance buffer against bad debt. Governance can deploy reserves or adjust the factor -- a higher reserve factor means lower supplier APY but stronger protocol solvency.

Gas Costs: Ethereum Mainnet vs Base

The cost of interacting with Compound varies significantly by network. On Ethereum mainnet, a supply or withdraw transaction requires roughly 150,000-200,000 gas units. At a gas price of 20 gwei and ETH at £2,500, that equates to approximately £7-12 per transaction under normal conditions. During network congestion (NFT mints, market volatility events), the same transaction can cost £30-60. Borrow and repay transactions are more complex, consuming 200,000-280,000 gas, pushing costs to £10-17 under normal conditions.

On Base -- Coinbase's L2, which runs a USDC Comet identical to the mainnet version -- the same operations cost under £0.05. Base settles to Ethereum and inherits its security guarantees, but posts transaction data as compressed calldata, which is why gas costs are roughly 100-300x cheaper. The USDC Comet on Base has grown to over $150M TVL, with USDC supply rates broadly matching the mainnet market. For positions under £10,000, Base is the more economical choice; mainnet only makes sense if you need the deeper liquidity or are already active there.

UK Tax Treatment of Lending Income

HMRC classifies interest earned on DeFi lending as miscellaneous income under its Cryptoassets Manual (CRYPTO60250 and CRYPTO60260). This means interest accrued on Compound -- whether in USDC, ETH, or any other token -- is taxable in the tax year it is received, at your marginal income tax rate (20%, 40%, or 45%). The sterling value at the moment of receipt is the figure to report.

COMP rewards received as governance incentives are also treated as income on receipt. When you later sell or swap those COMP tokens, a capital gains event arises on any increase in value between receipt and disposal. The £3,000 CGT annual exempt amount (2026/27) applies to net gains across all cryptoasset disposals in the tax year. Accurate record-keeping matters: tools such as Koinly and Accointing can import your Compound transaction history via wallet address and calculate both the income and CGT figures for your Self Assessment return. Given that DeFi rates update per block, your records should capture the sterling value at each accrual event or, where continuous accrual applies, at each point of actual receipt (i.e. when you withdraw or claim).

Institutional Use

DAOs and corporate treasuries use Compound to earn yield on idle stablecoin reserves while maintaining instant withdrawal access. The protocol's on-chain transparency provides a full audit trail -- every rate change, deposit, and liquidation is publicly verifiable, which simplifies compliance reporting. Institutional users typically interact through multi-sig wallets (Gnosis Safe) or dedicated custody solutions like Fireblocks that integrate directly with Compound's smart contracts.

Compound Treasury, the institutional product, offered fixed-rate USDC lending to accredited investors, though its adoption has been modest compared to Aave's institutional push. The protocol's conservative asset listing (fewer than 10 collateral types in V3) appeals to risk-averse institutions but limits flexibility compared to Aave's 100+ supported assets.

For UK-based DAOs or companies, the tax treatment of DeFi lending income warrants attention. Interest earned through Compound's lending markets is typically classified as trading income or miscellaneous income depending on the entity's activity profile. Companies holding stablecoins in a Compound Comet and earning interest will generally recognise that income under normal accruals accounting, with the sterling equivalent at each accounting period end determining the taxable figure. Unlike CeFi platforms that issue annual statements, Compound provides no tax reports -- finance teams must extract on-chain data programmatically via the Compound API or a third-party accounting tool.

Sources & References

• Compound Protocol Official Website
• Compound Protocol Documentation
• Compound Governance Portal
• Compound GitHub Repository

Honest Limitations

Before committing capital, you should understand where Compound falls short compared to alternatives:

• Fewer markets than Aave: Compound V3 supports fewer than 10 collateral types per Comet. Aave V3 lists 100+ assets across 7+ networks. If you hold mid-cap tokens, Compound likely will not accept them as collateral.
• Ethereum mainnet only (mostly): While Compound has expanded to Base and Arbitrum, its deepest liquidity remains on Ethereum L1, where a single supply transaction can cost $10-30 in gas. Smaller positions (under $5,000) lose a significant percentage of annual yield to gas fees.
• No flash loans: Unlike Aave, Compound does not offer native flash loans, limiting its utility for arbitrage and advanced DeFi strategies.
• Governance concentration: Approximately 10 delegates control a majority of COMP voting power. Proposals require 25,000 COMP (~$1M+) to create, which effectively limits governance participation to large holders and protocol-aligned entities.
• Lower supply rates: Because Compound's V3 architecture prioritises safety over capital efficiency, supply rates are typically 0.5-1% lower than Aave for comparable assets.
• No stable rate option: All borrowing on Compound uses variable rates. If you want predictable borrowing costs, Aave's stable rate option may suit you better.

Common Questions About Compound

What is Compound Protocol?

It is a decentralised lending protocol built on Ethereum that allows users to lend and borrow cryptocurrencies while earning interest on supplied assets. The protocol uses algorithmic interest rates that adjust automatically based on supply and demand, creating efficient money markets without traditional intermediaries.

How do I earn interest on Compound?

Supply supported cryptocurrencies to Compound's liquidity pools and automatically earn interest that compounds over time based on market demand. Interest rates are determined algorithmically and updated in real time, with earnings automatically added to your supplied balance without manual claiming.

What cryptocurrencies are supported on Compound?

It supports major cryptocurrencies, including ETH, USDC, USDT, DAI, WBTC, and other popular DeFi tokens. Each supported asset has its own market with specific collateral factors, reserve factors, and interest rate models optimised for that particular cryptocurrency's characteristics and market dynamics.

Is Compound safe to use?

It is a battle-tested DeFi protocol with extensive security audits from leading firms like OpenZeppelin and Trail of Bits, but like all DeFi platforms, it carries smart contract and market risks. The protocol has operated securely for years, with billions in total value locked, though users should understand the risks posed by smart contract vulnerabilities and market volatility.

How do I get started with Compound?

Connect a Web3 wallet like MetaMask to the Compound interface, supply assets to start earning interest immediately, or borrow against your collateral following the platform's collateral requirements. Ensure you have sufficient ETH for gas fees and understand the liquidation risks before borrowing.

What are COMP tokens and how do I earn them?

COMP tokens are Compound's governance tokens that allow holders to vote on protocol changes and parameter updates. Users earn COMP tokens automatically by supplying or borrowing assets on the protocol, with distribution rates determined by governance votes and updated regularly based on protocol usage and community decisions.

How does liquidation work on Compound?

If your borrowed amount exceeds the collateral factor due to price movements, your position becomes eligible for liquidation. Liquidators can repay up to 50% of your debt at a discount in exchange for your collateral, helping maintain protocol solvency while providing arbitrage opportunities for liquidators.

Can I use Compound for flash loans?

No. Compound does not offer native flash loans. If you need uncollateralised single-transaction borrowing, use Aave or dYdX instead. Developers can still build multi-step strategies that interact with Compound within a flash loan borrowed from another protocol.

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