---
title: readerInstanceIdentifier
framework: proximityreader
role: symbol
role_heading: Instance Property
path: proximityreader/mobiledocumentreader/configuration-swift.struct/readerinstanceidentifier
---

# readerInstanceIdentifier

The unique identifier for the mobile document reader instance.

## Declaration

```swift
let readerInstanceIdentifier: String
```

## Mentioned in

Generating reader tokens for the Verifier API

## Discussion

Discussion note: Do not cache this value. When generating a reader token always retrieve the latest reader instance identifier first.