PSA for Developers: Implementation of API Key requirements starting from February 15th, 2020 onwards.

The Etherscan Developer APIs are designed to provide the Ethereum community with accessible and consistent Ethereum data. The APIs are provided as a community service with a maximum rate limit of up to 5 calls per sec/IP.

As the APIs provided are open and unrestricted, developers can easily utilize them together with a free API key token (generated from the client portal). The API key acts as both a unique identifier and a secret token for authentication, and generally specify a set of access privileges that is specific to the identity associated with it. The API key also allows developers to monitor and to prevent malicious use, abuse and attacks on our end.

While our usage instructions and documentation have long advocated the required use of an API key for all requests (as per, this has not been enforced for more than a year to allow developers time to make the necessary changes.

Starting from February 15th, 2020 all developers are required to use a valid API key to access the API services provided by Etherscan. If you are already using a valid API key together with your call requests, then you are good to go. However, if you have not, please register for a free API key on our website. Failure to register and later use of an API will result in the return of an error stating “Invalid API Key.”

To register for an API key, developers must first register for an Etherscan account. If you do not have an Etherscan account, you can sign up using the instructions detailed in our knowledgebase. A single Etherscan account allows the creation of 3 API keys.

On the Etherscan user dashboard, you can select “API-KEYs” from the left-hand side column.

A pop up as below will appear when you click on “Create a new API-KEY token”. You can assign a name to the particular API key you intended to create.

When an API key is successfully created, a message will be shown as below:

You can now utilize the newly created API key for your applications.

Expected Return Error from API:

Invalid API Key:

{"status":"0","message":"NOTOK","result":"Error! Invalid API Key"}

The 5 calls per sec/IP rate limit is exceeded

{"status":"0","message":"NOTOK","result":"Maximum rate limit reached"}

If you face any issues creating an API key or using our API, kindly reach out to Etherscan Support.
Kaven Choi
Kaven Choi
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