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Base64 encode and decode strings


In this post, we’ll discuss how to Base64 encode and decode strings in Swift. We’ll then create extensions that make this a lot easier and more readable.

The basics

It’s very easy to Base64 encode strings in Swift. You just have to convert it to Data, then encode that data with base64EncodedString():

let string = "Let's encode this string"
let encoded = string.data(using: .utf8)?.base64EncodedString()

To decode a Base64 string, you just have to convert it to Data, then create a String from the decoded data:

guard let data = Data(base64Encoded: self) else { return nil }
return String(data: data, encoding: .utf8)

Note that both encoding and decoding can fail, which means that the operations produce optional strings.

Extending String

Although the above operations are very easy and straightforward, I prefer to use more convenient extensions, to avoid having to write the same code over and over.

To encode strings, I just wrap the encoding logic in a String extension:

func base64Encoded() -> String? {
    data(using: .utf8)?.base64EncodedString()
}

I also do the same for the decoding logic:

func base64Decoded() -> String? {
    guard let data = Data(base64Encoded: self) else { return nil }
    return String(data: data, encoding: .utf8)
}

We can now encode and decode strings like this:

let string = "Let's encode this string"
let encoded = string.base64Encoded()
let decoded = encoded?.base64Decoded()

I think that this is a lot cleaner. Since the decode logic requires a guard, you also save one line each time and avoid control flow where you may not want it.

Source code

I have added these extensions to my SwiftKit library. You can find the source code here and the unit tests here.