How to get file extension from base64 String in Flutter | Dart

Question

I have a base64 string of a document from api. I want to know which extension/file format is that. Because if it is in jpg/jpeg/png i want to show it in image widget. Or if it is in pdf format i want to show it in PdfView widget. So is there any way to get file extension from base64. Is there any package for it?

Answer 1

If you have a base64 string you can detect file type by checking the first character of your base64 string:

'/' means jpeg.

'i' means png.

'R' means gif.

'U' means webp.

'J' means PDF.

I wrote a function for that:

String getBase64FileExtension(String base64String) {
    switch (base64String.characters.first) {
      case '/':
        return 'jpeg';
      case 'i':
        return 'png';
      case 'R':
        return 'gif';
      case 'U':
        return 'webp';
      case 'J':
        return 'pdf';
      default:
        return 'unknown';
    }
  }