← all posts

Imports in Solidity

February 21, 2025 · 7 min read

Introduction

While completing a FreeCodeCamp course on Solidity, I initially struggled to understand imports. After some digging, I realized there are mainly three ways to import in Solidity:

Let's walk through each.

1. Local Imports

You can import both local and external files in Solidity.

For example,

In Same Folder

In Different Folder

2. Import Through GitHub (Works only in Remix)

There are many other ways to import other than GitHub in Remix. But I found this one too easy to follow. You just need to copy the GitHub URL pointing to the contract and paste it after import. Please find below e.g.

GitHub Import in Remix

3. Import in Brownie

Brownie is a great package for smart contract development. It is a Python-based development and testing framework for smart contracts targeting the Ethereum Virtual Machine.

There are two steps to follow:

Adding Dependency

To import a smart contract/source from a package, one needs to declare the dependencies by adding a dependencies field to your project configuration file. Brownie will download that dependency in the .brownie/packages folder during compilation.

The format to add dependency is [ORG]/[REPO]@[VERSION].

For e.g. let's import a smart contract from the Chainlink GitHub repo. To do so, we need to define dependency in the config file.

Dependencies

One thing to remember is that the repo must have a release version and tag associated with it. When you execute brownie compile, Brownie will download the package in the below location on your Windows machine.

Path Remappings

Now we need to do path remappings. Brownie exposes this functionality via the compiler.solc.remappings field in the configuration file. Each value under remappings is a string in the format prefix=path.

In simple words, it tells Brownie to search for a given prefix at a specific path. For e.g.

Path Remappings

Whenever @chainlink occurs in an import, it will tell Brownie that it refers to smartcontractkit/chainlink@1.3.0.

import '@chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol';

import 'smartcontractkit/chainlink@1.3.0/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol';

The above imports refer to the same thing.

References