---
title: Substring.Index
framework: swift
role: symbol
role_heading: Type Alias
path: swift/substring/index
---

# Substring.Index

A type that represents a position in the collection.

## Declaration

```swift
typealias Index = String.Index
```

## Discussion

Discussion Valid indices consist of the position of every element and a “past the end” position that’s not valid for use as a subscript argument.