Detects

• ASCII, UTF-8, UTF-16, UTF-32
• Big5, GB2312, EUC-TW, HZ-GB-2312, ISO-2022-CN (Traditional and Simplified Chinese)
• EUC-JP, SHIFT_JIS, CP932, ISO-2022-JP (Japanese)
• EUC-KR, ISO-2022-KR (Korean)
• KOI8-R, MacCyrillic, IBM855, IBM866, ISO-8859-5, windows-1251 (Cyrillic)
• ISO-8859-5, windows-1251 (Bulgarian)
• windows-1252 (English)
• ISO-8859-7, windows-1253 (Greek)
• ISO-8859-8, windows-1255 (Visual and Logical Hebrew)
• TIS-620 (Thai)

let data: Data = ... // a Data instance with unknown encoding
let (encoding: String, confidence: Double) =  SwiftyChardet.detect(data)

let data: Data = ... // a Data instance with unknown encoding
let text: String? = try? SwiftyChardet.decode(data)

pod install SwiftyChardet

For projects depends on Swift 2, Stick to 1.x branch