These are just a few simple logging utilities provided to simplify and standardize the error facilities across the Ethers library.

The Logger library has zero dependencies and is intentionally very light so it can be easily included in each library.

The Censorship functionality relies on one instance of the Ethers library being included. In large bundled packages or when npm link is used, this may not be the case. If you require this functionality, ensure that your bundling is configured properly.


new ethers.utils.Logger( version )

Create a new logger which will include version in all errors thrown.

Logger.globalLogger( ) Logger

Returns the singleton global logger.

Logging Output

logger.debug( ...args ) void

Log debugging information.

logger.info( ...args ) void

Log generic information.

logger.warn( ...args ) void

Log warnings.


These functions honor the current Censorship and help create a standard error model for detecting and processing errors within Ethers.

logger.makeError( message [ , code = UNKNOWN_ERROR [ , params ] ] ) Error

Create an Error object with message and an optional code and additional params set. This is useful when an error is needed to be rejected instead of thrown.

logger.throwError( message [ , code = UNKNOWN_ERROR [ , params ] ] ) never

Throw an Error with message and an optional code and additional params set.

logger.throwArgumentError( message , name , value ) never

Throw an INVALID_ARGUMENT Error with name and value.

Usage Validation

There can be used to ensure various properties and actions are safe.

logger.checkAbstract( target , kind ) void

If target is kind, throws a UNSUPPORTED_OPERATION error otherwise performs the same operations as checkNew.

This is useful for ensuring abstract classes are not being instantiated.

logger.checkArgumentCount( count , expectedCount [ , message ) void

If count is not equal to expectedCount, throws a MISSING_ARGUMENT or UNEXPECTED_ARGUMENT error.

logger.checkNew( target , kind ) void

If target is not a valid this or target value, throw a MISSING_NEW error. This is useful to ensure callers of a Class are using new.

logger.checkNormalize( message ) void

Check that the environment has a correctly functioning String.normalize. If not, a UNSUPPORTED_OPERATION error is thrown.

logger.checkSafeUint53( value [ , message ] ) void

If value is not safe as a JavaScript number, throws a NUMERIC_FAULT error.


Logger.setCensorship( censor [ , permanent = false ] ) void

Set error censorship, optionally preventing errors from being uncensored.

In production applications, this prevents any error from leaking information by masking the message and values of errors.

This can impact debugging, making it substantially more difficult.

Logger.setLogLevel( logLevel ) void

Set the log level, to suppress logging output below a particular log level.


Every error in Ethers has a code value, which is a string that will match one of the following error codes.

Generic Error Codes


The operation is not implemented. This may occur when calling a method on a sub-class that has not fully implemented its abstract superclass.


There was an error communicating with a server.

This may occur for a number of reasons, for example:

  • a CORS issue; this is quite often the problem and also the hardest to diagnose and fix, so it is very beneficial to familiarize yourself with CORS; some backends allow you configure your CORS, such as the geth command-line or conifguration files or the INFURA and Alchemy dashboards by specifing allowed Origins, methods, etc.
  • an SSL issue; for example, if you are trying to connect to a local node via HTTP but are serving the content from a secure HTTPS website
  • a link issue; a firewall is preventing the traffic from reaching the server
  • a server issue; the server is down, or is returning 500 error codes
  • a backend DDoS mitigation proxy; for example, Etherscan operates behind a Cloudflare proxy, which will block traffic if the request is sent via specific User Agents or the client fingerprint is detected as a bot in some cases


A timeout occurred.


A generic unknown error.


The operation is not supported.

This can happen for a variety reasons, for example:

Safety Error Codes


The amount of data needed is more than the amount of data required, which would cause the data buffer to read past its end.

This can occur if a contract erroneously returns invalid ABI-encoded data or RLP data is malformed.


There was an invalid operation done on numeric values.

Common cases of this occur when there is overflow, arithmetic underflow in fixed numeric types or division by zero.

Usage Error Codes


The type or value of an argument is invalid. This will generally also include the name and value of the argument. Any function which accepts sensitive data (such as a private key) will include the string "[[REDACTED]]" instead of the value passed in.


An expected parameter was not specified.


An object is a Class, but is not being called with new.


Too many parameters we passed into a function.

Ethereum Error Codes


An attempt to call a blockchain contract (getter) resulted in a revert or other error, such as insufficient gas (out-of-gas) or an invalid opcode. This can also occur during gas estimation or if waiting for a TransactionReceipt which failed during execution.

Consult the contract to determine the cause, such as a failed condition in a require statement. The reason property may provide more context for the cause of this error.


The account is attempting to make a transaction which costs more than is available.

A sending account must have enough ether to pay for the value, the gas limit (at the gas price) as well as the intrinsic cost of data. The intrinsic cost of data is 4 gas for each zero byte and 68 gas for each non-zero byte, as well as 35000 gas if a transaction contains no to property and is therefore expected to create a new account.


An Ethereum network validation error, such as an invalid chain ID.


The nonce being specified has already been used in a mined transaction.


When replacing a transaction, by using a nonce which has already been sent to the network, but which has not been mined yet the new transaction must specify a higher gas price.

This error occurs when the gas price is insufficient to bribe the transaction pool to prefer the new transaction over the old one. Generally, the new gas price should be about 50% + 1 wei more, so if a gas price of 10 gwei was used, the replacement should be 15.000000001 gwei. This is not enforced by the protocol, as it deals with unmined transactions, and can be configured by each node, however to ensure a transaction is propagated to a miner it is best practice to follow the defaults most nodes have enabled.


When a transaction has been replaced by the user, by broadcasting a new transaction with the same nonce as an existing in-flight (unmined) transaction in the mempool, this error will occur while waiting if the transaction being waited for has become invalidated by that other transaction.

This can happen for several reasons, but most commonly because the user has increased the gas price (which changes the transaction hash) to "speed up" a transaction or if a user has "cancelled" the transaction in their client. In either case this is usually accomplished by bribing the miners with a higher gas priced transaction.

This error will have the additional properties, cancelled, hash, reason, receipt and replacement.

See the TransactionResponse for the wait method for more details.


When estimating the required amount of gas for a transaction, a node is queried for its best guess.

If a node is unable (or unwilling) to predict the cost, this error occurs.

The best remedy for this situation is to specify a gas limit in the transaction manually.

This error can also indicate that the transaction is expected to fail regardless, if for example an account with no tokens is attempting to send a token.

Log Levels


Log all output, including debugging information.


Only log output for informational, warnings and errors.


Only log output for warnings and errors.


Only log output for errors.


Do not output any logs.