Gas fees are the payment a user makes to the blockchain network for executing a transaction. The fee compensates the validator or miner who includes the transaction in a block and covers the network's finite block-space budget.
On Ethereum, gas fees fluctuate with demand. A simple transfer might cost a few dollars during quiet periods and spike to $50+ during congestion (a hot NFT mint, a market-moving event). Fees are paid in the native asset — ETH on Ethereum, SOL on Solana, etc.
Layer-2 rollups (Arbitrum, Optimism, Base) drastically reduce gas: typical transactions cost sub-cent to a few cents. The L2 batches transactions off-chain, posts compressed state back to Ethereum, and shares Ethereum's security. For most users in 2026, L2s are the right default unless specifically transacting on L1.
A transaction's gas cost has two components: the compute cost of the operation (fixed per operation type) × the current "gas price" the network is charging (dynamic). Wallets estimate both automatically and typically set a reasonable priority fee for timely inclusion.