What Is Ethereum?
Ethereum is a decentralized, open-source blockchain that does more than transfer money. While Bitcoin was designed primarily as digital cash, Ethereum was built to be a general-purpose computing platform — sometimes called the “world computer.”
Launched in 2015 by Vitalik Buterin and a group of co-founders, Ethereum introduced the idea of a blockchain that could execute arbitrary programs called smart contracts. These programs live on the blockchain permanently, run exactly as written, and cannot be censored or shut down by any single entity.
That concept unlocked an entirely new category of applications: decentralized finance (DeFi) protocols that lend and borrow without banks, NFT marketplaces that trade digital ownership without intermediaries, decentralized autonomous organizations (DAOs) that coordinate resources through code, and much more.
If you are new to crypto entirely, start with our cryptocurrency for beginners guide and our blockchain explained guide. Both will give you the foundational knowledge that makes Ethereum easier to understand.
Ethereum vs Bitcoin
Bitcoin and Ethereum are the two largest cryptocurrencies, but they were designed for different purposes. Understanding those differences helps you see why Ethereum exists in the first place.
| Feature | Bitcoin | Ethereum |
|---|---|---|
| Purpose | Digital money and store of value | Programmable blockchain platform |
| Launched | 2009 | 2015 |
| Consensus | Proof of Work (mining) | Proof of Stake (staking) |
| Supply | Fixed at 21 million BTC | No hard cap; net deflationary since EIP-1559 |
| Block time | ~10 minutes | ~12 seconds |
| Throughput | ~7 TPS | ~15-30 TPS (L1); thousands with L2s |
| Smart contracts | Very limited (Script language) | Full-featured (Solidity, Vyper) |
| Energy use | High (mining hardware) | ~99.95% less after The Merge |
Neither is “better” in absolute terms. Bitcoin excels as a scarce, censorship-resistant monetary asset. Ethereum excels as a platform for building decentralized applications. Many crypto users hold both for different reasons.
Smart Contracts: Code That Runs Itself
A smart contract is a program stored on the Ethereum blockchain that executes automatically when predefined conditions are met. Once deployed, nobody can alter the code — it runs exactly as written, forever, unless the contract was specifically designed with an upgrade mechanism.
Think of a vending machine. You put in money, select an item, and the machine dispenses it. No cashier needed. A smart contract works the same way: you send a transaction that meets the contract’s conditions, and the contract executes the specified action. No intermediary needed.
What Smart Contracts Can Do
- Hold and transfer funds — A contract can receive ETH or tokens, hold them in escrow, and release them when conditions are met.
- Create tokens — The ERC-20 standard lets anyone create a new cryptocurrency on Ethereum. The ERC-721 standard powers NFTs.
- Run decentralized exchanges — Uniswap is entirely powered by smart contracts. No company processes trades; the code does.
- Manage lending pools — Aave and Compound use smart contracts to algorithmically set interest rates and manage collateral.
- Govern organizations — DAOs use smart contracts for voting and treasury management.
Smart Contract Languages
Most Ethereum smart contracts are written in Solidity, a language designed specifically for the EVM. Vyper is an alternative that prioritizes simplicity and security. Both compile down to EVM bytecode — the low-level instructions the Ethereum Virtual Machine actually executes.
Smart contracts are public. Anyone can read the code (if verified), audit the logic, and track every transaction. This transparency is a feature, not a bug — it means you do not have to trust a company, you can verify the code yourself. For a comprehensive look at smart contract security, real-world use cases, and how to interact with contracts safely, see our smart contracts explained guide.
The Ethereum Virtual Machine (EVM)
The Ethereum Virtual Machine is the engine that makes everything work. Every Ethereum node runs the EVM, and every smart contract executes inside it. When you send a transaction that interacts with a smart contract, every node on the network runs that same computation independently and arrives at the same result.
That is what makes Ethereum trustless: you do not need to trust any single computer because thousands of computers verify every operation.
How the EVM Processes Transactions
- You submit a transaction to the network (e.g., swap 1 ETH for USDC on Uniswap).
- Validators include your transaction in a block.
- The EVM on every node executes the smart contract code associated with your transaction.
- The result (your USDC balance increases, your ETH balance decreases) is recorded in the updated state.
- The block is finalized, and the state change becomes permanent.
EVM Compatibility: Why It Matters
The EVM has become the de facto standard for smart contract blockchains. Dozens of other chains — Polygon, BNB Chain, Avalanche, Arbitrum, Optimism, Base — are EVM-compatible. This means developers can write code once and deploy it across many networks with minimal changes. It also means wallets like MetaMask work across all these chains.
This network effect is one of Ethereum’s strongest competitive advantages. Even if a new chain is faster or cheaper, it often adopts EVM compatibility to attract developers who already know Solidity.
Gas Fees: What They Are and Why You Pay Them
Every computation on Ethereum costs gas. Gas is a unit that measures the computational effort required to execute an operation. Simple ETH transfers cost about 21,000 gas. Complex DeFi operations can cost hundreds of thousands of gas.
You pay gas fees in ETH. The total fee for a transaction is calculated as:
Total fee = Gas used × (Base fee + Priority tip)
Base Fee and Priority Tip
Since EIP-1559 (August 2021), Ethereum uses a two-part fee system:
- Base fee: Set by the protocol based on network demand. This portion is burned (destroyed), which makes ETH deflationary when the network is busy enough.
- Priority tip: An optional tip you add to incentivize validators to include your transaction faster. During congestion, higher tips get processed first.
For a deep dive into gas mechanics across different chains, read our complete gas fee guide. To estimate costs before you transact, use our gas fee estimator.
Why Gas Fees Spike
Ethereum blocks have limited space. When demand exceeds supply — during popular NFT mints, token launches, or market volatility — users bid up the priority tip to get their transactions included. This can push simple swap fees to $50-200 or more during peak periods.
Layer 2 networks solve this problem by moving most transactions off the main chain, which is why more and more users interact with Ethereum through Layer 2s rather than mainnet directly.
Proof of Stake and The Merge
From 2015 to September 2022, Ethereum used proof of work — the same energy-intensive mining system that Bitcoin uses. On September 15, 2022, Ethereum executed “The Merge,” switching to proof of stake. It was the largest infrastructure upgrade in crypto history, and it went off without a hitch.
How Proof of Stake Works on Ethereum
Instead of miners competing to solve math problems, proof of stake relies on validators who lock up (stake) 32 ETH as collateral. The protocol randomly selects validators to propose new blocks and verify other validators’ work.
- Validators deposit 32 ETH into the staking contract as a security bond.
- The protocol selects a proposer for each slot (every 12 seconds) to create a new block.
- Committees of validators attest to the validity of the proposed block.
- Honest validators earn rewards — currently about 3-4% APY on staked ETH.
- Dishonest validators get slashed — they lose a portion of their staked ETH as punishment.
For a detailed look at staking mechanics, rewards, and risks, read our complete staking guide. You can model your own staking returns with our staking calculator.
The Impact of The Merge
- Energy reduction: Ethereum’s energy consumption dropped by approximately 99.95%.
- Issuance reduction: New ETH issuance dropped by about 90%, making ETH net deflationary during periods of high network activity.
- Security model shift: Attacks now require acquiring a huge amount of ETH rather than hash power — making attacks economically punishing.
Layer 2 Scaling: Making Ethereum Affordable
Ethereum’s biggest challenge has always been scalability. Processing 15-30 transactions per second is not enough for a global financial system. Rather than sacrificing decentralization to increase throughput, Ethereum’s roadmap focuses on Layer 2 (L2) networks that handle transactions off the main chain and post compressed proofs back to Ethereum.
Types of Layer 2 Solutions
Optimistic Rollups
Optimistic rollups (Arbitrum, Optimism, Base) batch hundreds of transactions together and post the results to Ethereum. They assume transactions are valid by default (“optimistic”) and allow a challenge period (typically 7 days) during which anyone can dispute a fraudulent transaction. Most users never notice the challenge period because it only activates during disputes.
ZK-Rollups
Zero-knowledge rollups (zkSync, StarkNet, Scroll, Linea) use cryptographic proofs to verify transactions mathematically before posting them to Ethereum. This means they do not need a challenge period — finality is faster. ZK-rollups are more technically complex but are widely considered the long-term scaling solution.
| Layer 2 | Type | Typical fee | Finality |
|---|---|---|---|
| Arbitrum | Optimistic Rollup | $0.01-0.10 | ~7 day challenge |
| Optimism | Optimistic Rollup | $0.01-0.10 | ~7 day challenge |
| Base | Optimistic Rollup | $0.001-0.05 | ~7 day challenge |
| zkSync Era | ZK-Rollup | $0.01-0.20 | Minutes (with proof) |
| StarkNet | ZK-Rollup | $0.01-0.15 | Minutes (with proof) |
EIP-4844 and Blob Transactions
In March 2024, Ethereum implemented EIP-4844 (the Dencun upgrade), which introduced “blob” transactions — a new, cheaper way for Layer 2s to post data to Ethereum. This reduced L2 fees by 10-100x overnight. Some transactions on Base and Arbitrum now cost fractions of a penny.
The long-term roadmap (danksharding) will expand blob capacity further, making Layer 2 fees negligible for most users. For a comprehensive deep dive into all Layer 2 networks, bridging, and how to use them, see our Layer 2 solutions explained guide.
The Ethereum Ecosystem
Ethereum is not just one blockchain. It is an ecosystem of applications, protocols, Layer 2 networks, and developer tools that together form the largest smart contract platform in the world.
Decentralized Finance (DeFi)
DeFi is the largest category of Ethereum applications. DeFi protocols replace traditional financial services with smart contracts: Uniswap replaces stock exchanges, Aave replaces banks, Lido replaces staking services, and MakerDAO creates a decentralized stablecoin (DAI) without a central issuer.
As of early 2026, Ethereum and its Layer 2s hold the largest share of total value locked (TVL) across all DeFi protocols. Use our yield finder to compare current DeFi rates.
NFTs and Digital Ownership
Ethereum pioneered non-fungible tokens (NFTs) with standards like ERC-721 and ERC-1155. While the speculative NFT market cooled significantly from its 2021-2022 peak, the technology continues to find real utility in digital identity, gaming, ticketing, and intellectual property.
DAOs (Decentralized Autonomous Organizations)
DAOs use Ethereum smart contracts to coordinate groups of people around shared resources. Token holders vote on proposals, treasuries are managed transparently on-chain, and governance rules are enforced by code. Notable DAOs include Uniswap DAO, Aave DAO, and ENS DAO.
Developer Tools
Ethereum has the most mature developer ecosystem in crypto. Tools like Hardhat, Foundry, and Remix make it relatively straightforward to write, test, and deploy smart contracts. The large developer community means extensive documentation, tutorials, and open-source code to learn from.
Risks and Criticisms
Ethereum is a powerful platform, but it is not without risks and valid criticisms. Understanding these is essential before using the network or holding ETH.
- Smart contract risk: Bugs in smart contract code have led to hundreds of millions of dollars in losses. Even audited protocols can have vulnerabilities. Never deposit more than you can afford to lose into any DeFi protocol.
- Gas fee unpredictability: While Layer 2s have reduced fees dramatically, Ethereum mainnet can still be expensive during peak demand. A transaction you expected to cost $5 could cost $50 if network conditions change while you wait. Check our gas estimator before transacting.
- Complexity: Ethereum is harder to use than traditional finance. Wallets, gas fees, token approvals, bridging between layers, and managing private keys all add friction. Mistakes can be irreversible.
- Regulatory uncertainty: The regulatory status of ETH and Ethereum-based applications varies by jurisdiction and continues to evolve. This creates uncertainty for users and builders.
- Centralization vectors: While Ethereum is highly decentralized, concentration in staking (Lido’s market share), client software (Geth dominance), and infrastructure (cloud hosting) are ongoing concerns.
- MEV (Maximal Extractable Value): Validators and searchers can reorder, insert, or censor transactions to extract profit at users’ expense. While tools like Flashbots aim to mitigate this, MEV remains a structural challenge.
- Competition: Solana, Sui, Aptos, and other blockchains offer higher throughput and lower fees on their base layer. While Ethereum’s Layer 2 strategy addresses scalability, some argue that monolithic chains provide a simpler user experience.
Security Best Practices
If you use Ethereum, protect yourself:
- Use a hardware wallet for any significant holdings.
- Verify contract addresses before approving transactions.
- Start with established, audited protocols.
- Revoke unused token approvals regularly.
- Use our security checklist to audit your setup.