---
title: "isTrailSurrogate(_:)"
framework: swift
role: symbol
role_heading: Type Method
path: "swift/unicode/utf16/istrailsurrogate(_:)"
---

# isTrailSurrogate(_:)

Returns a Boolean value indicating whether the specified code unit is a low-surrogate code unit.

## Declaration

```swift
static func isTrailSurrogate(_ x: Unicode.UTF16.CodeUnit) -> Bool
```

## Parameters

- `x`: A UTF-16 code unit.

## Return Value

Return Value true if x is a low-surrogate code unit; otherwise, false.

## Discussion

Discussion Here’s an example of checking whether each code unit in a string’s utf16 view is a trailing surrogate. The apple string contains a single emoji character made up of a surrogate pair when encoded in UTF-16. let apple = "🍎" for unit in apple.utf16 {     print(UTF16.isTrailSurrogate(unit)) } // Prints "false" // Prints "true" This method does not validate the encoding of a UTF-16 sequence beyond the specified code unit. Specifically, it does not validate that a high-surrogate code unit precedes x.