1Overview

The Base64String scalar type represents an array of bytes encoded as a Base64 string. It is intended for scenarios where binary data needs to be transmitted, such as file contents, cryptographic keys, image data, or any arbitrary binary data.

Base64 encoding allows binary data to be safely represented as text in JSON and GraphQL, which natively only support text-based formats.

2Recommended name

The recommended name for this scalar is Base64String.

3Result spec

A Base64String scalar must serialize to a Base64-encoded string representing the binary data.

The Base64 encoding should follow RFC 4648, using the standard Base64 alphabet (A-Z, a-z, 0-9, +, /) with padding characters (=) as needed.

4Input spec

A Base64String scalar accepts Base64-encoded string values, both as GraphQL literals and as JSON input values.

The input must be a valid Base64-encoded string following RFC 4648. Implementations should validate that the input string contains only valid Base64 characters and proper padding.

Implementations should validate:

• String contains only valid Base64 characters (A-Z, a-z, 0-9, +, /, =)
• Padding is correct (0, 1, or 2 ‘=’ characters at the end)
• String length is valid for Base64 encoding (multiple of 4 characters after padding)

mutation {
  uploadFile(content: "SGVsbG8gV29ybGQ=") {
    id
  }
}

{
  "content": "SGVsbG8gV29ybGQ="
}

{
  "thumbnail": "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mNk+M9QDwADhgGAWjR9awAAAABJRU5ErkJggg=="
}

5References

• RFC 4648 — The Base64 Data Encoding