Cross-Origin Resource Sharing (CORS)

I recently made my first API, and when making an API, you need to configure CORS, or Cross-Origin Resource Sharing, when you deploy it online.

I recently made my first API, and when making an API, you need to configure CORS, or Cross-Origin Resource Sharing, when you deploy it online. Basically, you need to specify which website or domain can make a request to the API, for example https://example.com.

But when you are developing locally on your own computer, you don’t necessarily need to specify which website can access it since you just make your request using http://localhost:port-number, but sooner or later you’re still going to want to host your API online, so you’re going to need to setup CORS.

Setting Up CORS in Node.js with Express

Install cors middleware using npm install cors
Inside the index.js:

app.use(
  cors({
    origin: "https://memarandom.onrender.com", //specify the allowed origin
  }),
);

Origin is where you specify what domains can make a request to the API; it can also take multiple origins.

Allowing Multiple Origins

To allow multiple origins, you have to make an array of origins as a string:

origin: ["https://memarandom.onrender.com", "https://your-website.com"],

Open Access for public APIs

If you are making an API that is open for the public or that you want any websites to make a GET request, you can use an asterisk ”*,” called a wildcard, to allow all websites:

origin: "*",

Caution You need to be very careful when using it, as it can lead to a potential security risk because you know it’s an “aste—RISK”.

Anyway, the API I just made is memarandom; it generates random memes from the memes that I have personally seen and laughed at. <br/> If you have any corrections to this blog, please contact me or open an issue in the git repository.

Understanding Cross-Origin Resource Sharing (CORS) for an API

Setting Up CORS in Node.js with Express