---
title: "canonicalRequest(for:)"
framework: foundation
role: symbol
role_heading: Type Method
path: "foundation/urlprotocol/canonicalrequest(for:)"
---

# canonicalRequest(for:)

Returns a canonical version of the specified request.

## Declaration

```swift
class func canonicalRequest(for request: URLRequest) -> URLRequest
```

## Parameters

- `request`: The request whose canonical version is desired.

## Return Value

Return Value The canonical form of request.

## Discussion

Discussion It is up to each concrete protocol implementation to define what “canonical” means. A protocol should guarantee that the same input request always yields the same canonical form. Special consideration should be given when implementing this method, because the canonical form of a request is used to lookup objects in the URL cache, a process which performs equality checks between URLRequest instances. This is an abstract method and subclasses must provide an implementation.