Detect Base-64

General
21

Perhaps that is your key, then. Use TextEncoding.IsValidData to test for the encodings you expect (UTF8, etc).

22

Is this an existing XOJO feature? is so, I cannot find it any any docs

23

ok… not extensively tested yet…

FUNCTION isBase64(byRef s As String) As Boolean
  Dim d As String
  Dim e As String
  d=DecodeBase64(s)
  If Encodings.UTF8.IsValidData(d) Then
    e=EncodeBase64(d)
    If (e=s) Then 
      s=d
      Return True
    End If
  End If
  Return False
END FUNCTION

Also if it IS a Base 64 string, it returns the decode version