Web3 New Added 26 September 2026

Web3: max code size exceeded when deploying a contract

EIP-170 caps deployed runtime code at 24576 bytes and the deployment is rejected once the compiled contract passes it. The growth is usually incidental rather than a single large addition: long revert strings, many public functions and inlined library code all count, and building with the optimiser off can be the whole difference.

Quick fix

Read the commands before running them. Anything that restarts a service, deletes data or changes permissions should be tried on a non-production system first.

Quick fix

# Measure first, the number tells you how much has to go
forge build --sizes
npx hardhat compile && npx hardhat size-contracts

// The optimiser alone often brings it back under the cap
// hardhat.config.js
solidity: { version: '0.8.28', settings: { optimizer: { enabled: true, runs: 200 } } }
// foundry.toml: optimizer = true, optimizer_runs = 200

// Custom errors replace revert strings and cost bytecode as well as gas
error NotOwner();

// External library functions deploy separately and are linked in
library Fees { function apply(uint a) external pure returns (uint) { return a; } }

// Past that, split the contract: a proxy with facets keeps each piece small

# Local chains can lift the limit for tests, mainnet cannot
# anvil --code-size-limit 50000

How to diagnose Web3 errors

Web3 errors are unusually terse because the EVM reports failure without explanation by default. execution reverted means a require or revert triggered. The reason string is present in the return data but most libraries discard it. Nonce errors reflect the strict sequential ordering of transactions per account, so a stuck transaction blocks every one behind it.

If the quick fix above does not resolve it, work through these steps. They apply to this whole class of error, not just to this one message, which is usually what saves the time.

Simulate before sending: eth_call against the same block returns the revert reason string that a submitted transaction hides.
Use a transaction tracer (Tenderly, Foundry's cast run, or a node's debug_traceTransaction) to see the exact opcode and contract where execution reverted.
For nonce errors, query the account's pending nonce (eth_getTransactionCount with the pending tag) rather than tracking it locally.
To replace a stuck transaction, resend with the same nonce and a materially higher gas price: most nodes require at least a 10% increase.
Check the chain ID matches the network you intend. Signing for the wrong chain produces confusing rejection messages.

Tools worth reaching for

cast (Foundry)
eth_call simulation
Tenderly / block explorer tracer
debug_traceTransaction

Authoritative references

Primary documentation for this error, worth reading before applying any fix in production.

eips.ethereum.org docs.soliditylang.org

Related Web3 errors

See all 17 Web3 errors →

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