# ERC-165 Primer

By [0xNelli](https://paragraph.com/@0xnelli) · 2024-11-14

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Overview
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ERC-165 is an interface identification mechanism that enhances compossibility as contracts can determine whether a contract supports an interface at compile time.

ERC-165 Goal
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Prior to ERC-165, there was no mechanism to check whether a contract supported a specific interface, such as ERC-20. Therefore, there was no way of verifying whether a contract could accept tokens or tokens sent to a contract would be ‘stuck’ and effectively lost.

Implementation
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ERC-165 introduces a standardized function to declare support for specific interfaces within a given contract. Other contracts can call this function to verify whether a certain interface is supported.

    function supportsInteface(bytes4 interfaceId) external view returns (bool);
    

### Supporting multiple Interfaces

In the wild you may have observed something like this:

    function supportsInterface(bytes4 interfaceId) public view    override(ERC1155, AccessControl) returns (bool) { 
        return super.supportsInterface(interfaceId); 
    }
    

This is required when a contract inherits multiple instances of `supportsInterface` for different interface standards. In the example above, the contract inherits from both ERC-1155 and Access Control. The contract must override `supportsInterface` function and uses the `super` keyword to specify that the contract's own `supportsInteface` function should combine the from both interfaces. This way the `supportsInterface` function will return `true` for both queries with ERC-1155 and Access Control.

Sources
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1.  [https://eips.ethereum.org/EIPS/eip-165](https://eips.ethereum.org/EIPS/eip-165)

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*Originally published on [0xNelli](https://paragraph.com/@0xnelli/erc-165-primer)*