diff --git a/.gitignore b/.gitignore
index 5fbae6e..ae9498c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,3 +4,4 @@
 *.xcworkspace/
 xcuserdata/
 /.swiftpm
+/.vscode
diff --git a/Package.swift b/Package.swift
index c164678..567572c 100644
--- a/Package.swift
+++ b/Package.swift
@@ -1,4 +1,4 @@
-// swift-tools-version:5.2
+// swift-tools-version:6.0
 // The swift-tools-version declares the minimum version of Swift required to build this package.
 
 import PackageDescription
@@ -6,10 +6,10 @@ import PackageDescription
 let package = Package(
   name: "HTTPFluent",
   platforms: [
-    .macOS(.v10_15),
-    .iOS(.v13),
-    .tvOS(.v13),
-    .watchOS(.v6)
+    .macOS(.v13),
+    .iOS(.v16),
+    .tvOS(.v16),
+    .watchOS(.v9)
   ],
   products: [
     // Products define the executables and libraries produced by a package, and make them visible to other packages.
diff --git a/README.md b/README.md
index 50754c7..5c713be 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,66 @@
 # HTTPFluent
 
-HTTPFluent provides a fluent interface over HTTP, primarily designed to work with APIs. HTTPFluent supports three styles: callback, `async` (with Swift >= 5.5) and Combine.
+HTTPFluent provides a fluent interface over HTTP, primarily designed to work with APIs. HTTPFluent supports three styles: callback, `async` (with Swift >= 5.5) and Combine (on Apple platforms).
+
+## Integration
+
+HTTPFluent is available only via Swift Package Manager.
+
+## Usage
+
+HTTPFluent is extremely intuitive to use, so a few examples will suffice:
+
+```swift
+let id = 2349713
+let jwt = "xyz123"
+
+let request = URLClient(url: "https://myapi.com")
+  .path("user", id)
+  .authorization(bearer: jwt)
+  .post(json: User(name: "Don Quixote"))
+
+// Callback style
+request.receive(json: User.self) { result in
+  do {
+    let user = try result.get()
+  } catch {
+    // Oops, no user
+  }
+}
+
+// Async style
+let user = try await request.receive(json: User.self)
+
+// Combine style
+request.receivePublisher(json: User.self)
+  .sink { completion in
+    // Handle completion
+  } receiveValue: { user in
+    // Do something with user
+  }
+  .store(in: &cancellables)
+```
+
+HTTPFluent can also be used to generate a `URLRequest` without invoking it.
+
+```swift
+let urlRequest = URLClient(url: "https://myapi.com")
+  .path("user", id)
+  .authorization(bearer: jwt)
+  .put(data: data) // Here we put raw data instead of JSON.
+  .request
+```
+
+HTTPFluent uses immutable state. Each step in the chain to build the `URLRequest` copies a `URLRequestBuilder` struct. All operations are thus additive, encouraging reuse.
+
+```swift
+// Set up the shared information about the request.
+let fluent = URLClient(url: "https://myapi.com")
+  .authorization(bearer: jwt)
+  .path("user")
+
+// This adds the value of id as a path element, so the result is
+// the path /user/123 or whatever the value of id is.
+let postWithId = fluent.path(id).post(json: User.self)
+let user = try await postWithId.receive(json: User.self)
+```
diff --git a/Sources/HTTPFluent/Combine+Shim.swift b/Sources/HTTPFluent/Combine+Shim.swift
deleted file mode 100644
index 550ce0e..0000000
--- a/Sources/HTTPFluent/Combine+Shim.swift
+++ /dev/null
@@ -1,20 +0,0 @@
-//
-//  Combine+Shim.swift
-//  HTTPFluent
-//
-//  Created by Gregory Higley on 8/12/20.
-//
-
-import Foundation
-
-#if !canImport(Combine)
-public protocol TopLevelDecoder {
-  associatedtype Input
-  func decode<T: Decodable>(_ type: T.Type, from: Input) throws -> T
-}
-
-public protocol TopLevelEncoder {
-  associatedtype Output
-  func encode<T: Encodable>(_ value: T) throws -> Output
-}
-#endif
diff --git a/Sources/HTTPFluent/ConstantValue.swift b/Sources/HTTPFluent/ConstantValue.swift
index a078402..bfb40b5 100644
--- a/Sources/HTTPFluent/ConstantValue.swift
+++ b/Sources/HTTPFluent/ConstantValue.swift
@@ -3,11 +3,15 @@
 //  HttpFluent
 //
 //  Created by Gregory Higley on 2020-07-18.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
 import Foundation
 
-public protocol ConstantValue: RawRepresentable & Hashable & ExpressibleByStringLiteral & CustomStringConvertible where RawValue == String {
+public protocol ConstantValue:
+  RawRepresentable, Hashable, ExpressibleByStringLiteral, CustomStringConvertible, Sendable where RawValue == String
+{
   init(constantValue value: String)
 }
 
diff --git a/Sources/HTTPFluent/Decoders.swift b/Sources/HTTPFluent/Decoders.swift
index b497f49..a24600c 100644
--- a/Sources/HTTPFluent/Decoders.swift
+++ b/Sources/HTTPFluent/Decoders.swift
@@ -2,14 +2,19 @@
 //  Decoder.swift
 //  HTTPFluent
 //
-//  Created by Gregory Higley on 8/10/20.
+//  Created by Gregory Higley on 2020-08-12.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
-import Combine
 import Foundation
 
-public struct Decoders {
-  public typealias Decode<T> = (Data) throws -> T
+#if canImport(Combine)
+import Combine
+#endif
+
+public struct Decoders: Sendable {
+  public typealias Decode<T> = @Sendable (Data) throws -> T
   
   public static func string(encoding: String.Encoding) -> Decode<String> {
     return { data in
@@ -22,7 +27,7 @@ public struct Decoders {
 
   public static let string: Decode<String> = Self.string(encoding: .utf8)
   
-  public static func decode<T: Decodable, Decoder: TopLevelDecoder>(_ type: T.Type, with decoder: Decoder) -> Decode<T> where Decoder.Input == Data {
+  public static func decode<T: Decodable & Sendable, Decoder: TopLevelDecoder & Sendable>(_ type: T.Type, with decoder: Decoder) -> Decode<T> where Decoder.Input == Data {
     return { data in
       do {
         return try decoder.decode(type, from: data)
@@ -32,7 +37,7 @@ public struct Decoders {
     }
   }
     
-  public static func json<T: Decodable>(_ type: T.Type) -> Decode<T> {
+  public static func json<T: Decodable & Sendable>(_ type: T.Type) -> Decode<T> {
     return decode(type, with: JSONDecoder())
   }
 }
diff --git a/Sources/HTTPFluent/FormData.swift b/Sources/HTTPFluent/FormData.swift
index 29e380d..904d665 100644
--- a/Sources/HTTPFluent/FormData.swift
+++ b/Sources/HTTPFluent/FormData.swift
@@ -3,7 +3,8 @@
 //  HTTPFluent
 //
 //  Created by Gregory Higley on 2020-05-09.
-//  Copyright © 2020 Prosumma. All rights reserved.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
 import Foundation
@@ -24,8 +25,8 @@ import Foundation
  let data = form.encoded()
  ```
  */
-public struct FormData {
-  public enum Encoding {
+public struct FormData: @unchecked Sendable {
+  public enum Encoding: Sendable {
     case urlEncoded
     case formEncoded
   }
@@ -35,7 +36,7 @@ public struct FormData {
    `FormData` instance is encoded as "application/x-www-form-urlencoded",
    instances of this type are skipped without warning.
    */
-  public struct File {
+  public struct File: Sendable {
     public let filename: String
     public let content: Data
     public let headers: [String: String]
diff --git a/Sources/HTTPFluent/HTTPHeaderField.swift b/Sources/HTTPFluent/HTTPHeaderField.swift
index cb3745b..00365ef 100644
--- a/Sources/HTTPFluent/HTTPHeaderField.swift
+++ b/Sources/HTTPFluent/HTTPHeaderField.swift
@@ -3,7 +3,8 @@
 //  HTTPFluent
 //
 //  Created by Gregory Higley on 2020-05-08.
-//  Copyright © 2020 Prosumma. All rights reserved.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
 import Foundation
diff --git a/Sources/HTTPFluent/HTTPMethod.swift b/Sources/HTTPFluent/HTTPMethod.swift
index 7b41eaa..2968e28 100644
--- a/Sources/HTTPFluent/HTTPMethod.swift
+++ b/Sources/HTTPFluent/HTTPMethod.swift
@@ -3,7 +3,8 @@
 //  HTTPFluent
 //
 //  Created by Gregory Higley on 2020-05-08.
-//  Copyright © 2020 Prosumma. All rights reserved.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
 import Foundation
diff --git a/Sources/HTTPFluent/MimeType.swift b/Sources/HTTPFluent/MimeType.swift
index 6ff6787..35755b4 100644
--- a/Sources/HTTPFluent/MimeType.swift
+++ b/Sources/HTTPFluent/MimeType.swift
@@ -3,7 +3,8 @@
 //  HTTPFluent
 //
 //  Created by Gregory Higley on 2020-05-08.
-//  Copyright © 2020 Prosumma. All rights reserved.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
 import Foundation
diff --git a/Sources/HTTPFluent/Publisher.swift b/Sources/HTTPFluent/Publisher.swift
index f890f95..18b9462 100644
--- a/Sources/HTTPFluent/Publisher.swift
+++ b/Sources/HTTPFluent/Publisher.swift
@@ -3,9 +3,10 @@
 //  HTTPFluent
 //
 //  Created by Gregory Higley on 2020-07-13.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
-#if canImport(Combine)
 import Combine
 
 @available(macOS 10.15, iOS 13.0, tvOS 13.0, watchOS 6.0, *)
@@ -26,4 +27,3 @@ public extension Publisher {
     return mapErrorIfNeeded(URLError.error)
   }
 }
-#endif
diff --git a/Sources/HTTPFluent/URLClient.swift b/Sources/HTTPFluent/URLClient.swift
index 2f2bf8c..4fc6440 100644
--- a/Sources/HTTPFluent/URLClient.swift
+++ b/Sources/HTTPFluent/URLClient.swift
@@ -3,56 +3,47 @@
 //  HTTPFluent
 //
 //  Created by Gregory Higley on 2020-05-08.
-//  Copyright © 2020 Prosumma. All rights reserved.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
-#if canImport(Combine)
 import Combine
-#endif
-
 import Foundation
 
-/**
- Perform HTTP operations on a base URL.
-
- Most uses of HTTP at Patron and other organizations
- perform one or more operations against some API hosted
- at a specific base URL. `HTTPClient` makes this very
- easy and natural using a fluent interface.
-
- This is best illustrated with an example:
+#if canImport(FoundationNetworking)
+import FoundationNetworking
+#endif
 
- ```swift
- let jwt: String = "...imagine a JWT..."
- let token = "xyz123"
- let attendee = Attendee(token: token)
- let client = HTTPClient(url: "https://api.patron.com/api")
- client
-   .path("attendee", token) // api/attendee/xyz123
-   .query(7, forName: "x") // ?x=7
-   .authorization(bearer: jwt)
-   .post(json: attendee)
-   .dataTaskPublisher(decoding: AttendeeResponse.self)
- ```
- */
-public struct URLClient {
-  public typealias ResponseHandler = (Data?, URLResponse?) throws -> Data
+public struct URLClient: Sendable {
+  public typealias ResponseHandler = @Sendable (Data?, URLResponse?) throws -> Data
   
   let session: URLSession
   var builder: URLRequestBuilder
   let responseHandler: ResponseHandler
 
-  public init(builder: URLRequestBuilder, session: URLSession = URLSession(configuration: .ephemeral), responseHandler: @escaping ResponseHandler = URLClient.defaultResponseHandler) {
+  public init(
+    builder: URLRequestBuilder,
+    session: URLSession = URLSession(configuration: .ephemeral),
+    responseHandler: @escaping ResponseHandler = URLClient.defaultResponseHandler
+  ) {
     self.session = session
     self.builder = builder
     self.responseHandler = responseHandler
   }
 
-  public init(url: URL, session: URLSession = URLSession(configuration: .ephemeral), responseHandler: @escaping ResponseHandler = URLClient.defaultResponseHandler) {
+  public init(
+    url: URL,
+    session: URLSession = URLSession(configuration: .ephemeral),
+    responseHandler: @escaping ResponseHandler = URLClient.defaultResponseHandler
+  ) {
     self.init(builder: URLRequestBuilder(url: url), session: session, responseHandler: responseHandler)
   }
 
-  public init(url: String, session: URLSession = URLSession(configuration: .ephemeral), responseHandler: @escaping ResponseHandler = URLClient.defaultResponseHandler) {
+  public init(
+    url: String,
+    session: URLSession = URLSession(configuration: .ephemeral),
+    responseHandler: @escaping ResponseHandler = URLClient.defaultResponseHandler
+  ) {
     self.init(builder: URLRequestBuilder(url: url), session: session, responseHandler: responseHandler)
   }
   
@@ -72,8 +63,7 @@ extension URLClient: URLClientProtocol {
     builder.request
   }
 
-  @available(macOS 10.15, iOS 13.0, tvOS 13.0, watchOS 6.0, *)
-  public var publisher: AnyPublisher<Data, URLError> {
+  public var receivePublisher: AnyPublisher<Data, URLError> {
     request.publisher.flatMap { req in
       self.session
         .dataTaskPublisher(for: req)
@@ -82,14 +72,17 @@ extension URLClient: URLClientProtocol {
     }.eraseToAnyPublisher()
   }
   
-  public func receive(on queue: DispatchQueue = DispatchQueue.global(), callback: @escaping (URLResult<Data>) -> Void) {
+  public func receive(on queue: DispatchQueue = DispatchQueue.global(), callback: @escaping @Sendable (URLResult<Data>) -> Void) {
     switch request {
     case .failure(let error):
       queue.async { callback(.failure(error)) }
     case .success(let request):
       let task = session.dataTask(with: request) { (data, response, error) in
         var result: URLResult<Data> = .failure(.unknown)
-        defer { queue.async { callback(result) } }
+        defer {
+          let result = result
+          queue.async { callback(result) }
+        }
         if let error = error {
           return result = .failure(.error(error))
         }
@@ -105,17 +98,24 @@ extension URLClient: URLClientProtocol {
     }
   }
   
-  #if swift(>=5.5)
-
-  @available(macOS 12.0, iOS 15.0, tvOS 15.0, watchOS 8.0, *)
   public func receive() async throws -> Data {
     switch request {
     case .failure(let error):
       throw error
     case .success(let request):
-      let (data, response): (Data, URLResponse)
+      let (data, response): (Data?, URLResponse?)
       do {
-        (data, response) = try await session.data(for: request)
+        #if os(Linux)
+          (data, response) = try await withCheckedThrowingContinuation { continuation in
+            let task = session.dataTask(with: request) { (data, response, error) in
+              if let error = error { continuation.resume(throwing: error) }
+              continuation.resume(returning: (data, response))
+            }
+            task.resume()
+          }
+        #else
+          (data, response) = try await session.data(for: request)
+        #endif
       } catch {
         throw URLError.error(error)
       }
@@ -123,9 +123,6 @@ extension URLClient: URLClientProtocol {
     }
   }
 
-  #endif
-
-    
   public func build(_ apply: (inout URLRequestBuilder) -> Void) -> URLClient {
     var client = self
     apply(&client.builder)
diff --git a/Sources/HTTPFluent/URLClientProtocol+Async.swift b/Sources/HTTPFluent/URLClientProtocol+Async.swift
index 88ed029..4d32fe7 100644
--- a/Sources/HTTPFluent/URLClientProtocol+Async.swift
+++ b/Sources/HTTPFluent/URLClientProtocol+Async.swift
@@ -3,35 +3,28 @@
 //  HTTPFluent
 //
 //  Created by Gregory Higley on 2021-12-25.
-//  Copyright © 2020 Prosumma. All rights reserved.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
-#if canImport(Combine)
 import Combine
-#endif
-
 import Foundation
 
-#if swift(>=5.5)
-
-@available(macOS 12.0, iOS 15.0, tvOS 15.0, watchOS 8.0, *)
 public extension URLClientProtocol {
-  func receive<Response>(decode: @escaping Decoders.Decode<Response>) async throws -> Response {
+  func receive<Response: Sendable>(decode: @escaping Decoders.Decode<Response>) async throws -> Response {
     try decode(await receive())
   }
 
-  func receive<Response, Decoder>(
+  func receive<Response: Sendable, Decoder: Sendable>(
     decoding type: Response.Type = Response.self,
     decoder: Decoder
   ) async throws -> Response where Response: Decodable, Decoder: TopLevelDecoder, Decoder.Input == Data {
     try await receive(decode: Decoders.decode(type, with: decoder))
   }
 
-  func receive<Response: Decodable>(
+  func receive<Response: Decodable & Sendable>(
     json type: Response.Type
   ) async throws -> Response {
     try await receive(decode: Decoders.json(type))
   }
 }
-
-#endif
diff --git a/Sources/HTTPFluent/URLClientProtocol+Combine.swift b/Sources/HTTPFluent/URLClientProtocol+Combine.swift
index d36a857..6438597 100644
--- a/Sources/HTTPFluent/URLClientProtocol+Combine.swift
+++ b/Sources/HTTPFluent/URLClientProtocol+Combine.swift
@@ -2,16 +2,14 @@
 //  URLClientProtocol+Combine.swift
 //  HTTPFluent
 //
-//  Created by Gregory Higley on 8/12/20.
+//  Created by Gregory Higley on 2020-08-12.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
-#if canImport(Combine)
 import Combine
-#endif
-
 import Foundation
 
-@available(macOS 10.15, iOS 13.0, tvOS 13.0, watchOS 6.0, *)
 public extension URLClientProtocol {
   /**
    Decodes the `Data` in the published stream using `decode`.
@@ -29,10 +27,10 @@ public extension URLClientProtocol {
    `Decoders.string` is a function which decodes from `Data`
    to `String`, assuming the underlying `Data` is UTF-8.
    */
-  func publisher<Response>(
+  func receivePublisher<Response>(
     decode: @escaping Decoders.Decode<Response>
   ) -> AnyPublisher<Response, URLError> {
-    publisher.tryMap(decode).mapErrorIfNeeded(URLError.decoding).eraseToAnyPublisher()
+    receivePublisher.tryMap(decode).mapErrorIfNeeded(URLError.decoding).eraseToAnyPublisher()
   }
   
   /**
@@ -42,19 +40,18 @@ public extension URLClientProtocol {
    If `decoder` is `JSONDecoder`, the `Accept: application/json` is sent
    automatically with the request.
    */
-  func publisher<Response, Decoder>(
+  func receivePublisher<Response: Sendable, Decoder: Sendable>(
     decoding type: Response.Type = Response.self,
     decoder: Decoder
   ) -> AnyPublisher<Response, URLError> where Response: Decodable, Decoder: TopLevelDecoder, Decoder.Input == Data {
     let fluent = decoder is JSONDecoder ? accept(.json) : self
-    return fluent.publisher(decode: Decoders.decode(type, with: decoder))
+    return fluent.receivePublisher(decode: Decoders.decode(type, with: decoder))
   }
 
   /// Decodes the `Data` in the published stream using a default `JSONDecoder`.
-  func publisher<Response: Decodable>(
+  func receivePublisher<Response: Decodable & Sendable>(
     json type: Response.Type = Response.self
   ) -> AnyPublisher<Response, URLError> {
-    accept(.json).publisher(decode: Decoders.json(type))
+    accept(.json).receivePublisher(decode: Decoders.json(type))
   }
-
 }
diff --git a/Sources/HTTPFluent/URLClientProtocol+Receive.swift b/Sources/HTTPFluent/URLClientProtocol+Receive.swift
index 198ab37..1daea23 100644
--- a/Sources/HTTPFluent/URLClientProtocol+Receive.swift
+++ b/Sources/HTTPFluent/URLClientProtocol+Receive.swift
@@ -2,13 +2,12 @@
 //  URLClientProtocol+Receive.swift
 //  HTTPFluent
 //
-//  Created by Gregory Higley on 8/12/20.
+//  Created by Gregory Higley on 2020-08-12.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
-#if canImport(Combine)
 import Combine
-#endif
-
 import Foundation
 
 //swiftlint:disable function_default_parameter_at_end
@@ -22,7 +21,7 @@ public extension URLClientProtocol {
    */
   func receive(
     on queue: DispatchQueue = DispatchQueue.global(),
-    callback: @escaping (URLResult<Data>) -> Void)
+    callback: @escaping @Sendable (URLResult<Data>) -> Void)
   {
     receive(on: queue, callback: callback)
   }
@@ -36,7 +35,7 @@ public extension URLClientProtocol {
   func receive<Response>(
     on queue: DispatchQueue = DispatchQueue.global(),
     decode: @escaping Decoders.Decode<Response>,
-    callback: @escaping (URLResult<Response>) -> Void
+    callback: @escaping @Sendable (URLResult<Response>) -> Void
   ) {
     receive(on: queue) { result in
       do {
@@ -49,11 +48,11 @@ public extension URLClientProtocol {
     }
   }
     
-  func receive<Response, Decoder>(
+  func receive<Response, Decoder: Sendable>(
     decoding type: Response.Type = Response.self,
     decoder: Decoder,
     on queue: DispatchQueue = DispatchQueue.global(),
-    callback: @escaping (URLResult<Response>) -> Void
+    callback: @escaping @Sendable (URLResult<Response>) -> Void
   ) where Response: Decodable, Decoder: TopLevelDecoder, Decoder.Input == Data {
     let fluent = decoder is JSONDecoder ? accept(.json) : self
     return fluent.receive(on: queue, decode: Decoders.decode(type, with: decoder), callback: callback)
@@ -62,7 +61,7 @@ public extension URLClientProtocol {
   func receive<Response>(
     json type: Response.Type = Response.self,
     on queue: DispatchQueue = DispatchQueue.global(),
-    callback: @escaping (URLResult<Response>) -> Void
+    callback: @escaping @Sendable (URLResult<Response>) -> Void
   ) where Response: Decodable {
     receive(on: queue, decode: Decoders.json(type), callback: callback)
   }
diff --git a/Sources/HTTPFluent/URLClientProtocol.swift b/Sources/HTTPFluent/URLClientProtocol.swift
index 3f19c1a..292a60a 100644
--- a/Sources/HTTPFluent/URLClientProtocol.swift
+++ b/Sources/HTTPFluent/URLClientProtocol.swift
@@ -3,13 +3,11 @@
 //  HTTPFluent
 //
 //  Created by Gregory Higley on 2020-05-08.
-//  Copyright © 2020 Prosumma. All rights reserved.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
-#if canImport(Combine)
 import Combine
-#endif
-
 import Foundation
 
 /**
@@ -20,17 +18,16 @@ public protocol URLClientProtocol: URLRequestBuilderProtocol {
   /**
    Publishes the `Data` result of executing the underlying `URLRequest`.
    */
-  @available(macOS 10.15, iOS 13.0, tvOS 13.0, watchOS 6.0, *)
-  var publisher: AnyPublisher<Data, URLError> { get }
-  
-#if swift(>=5.5)
-  @available(macOS 12.0, iOS 15.0, tvOS 15.0, watchOS 8.0, *)
+  var receivePublisher: AnyPublisher<Data, URLError> { get }
+
+  /**
+   Gets the result of the `URLRequest` asynchronously as `Data`.
+   */
   func receive() async throws -> Data
-#endif
 
   /**
    Executes the underlying `URLRequest` and calls `callback` on the given `queue` when it
    completes.
    */
-  func receive(on queue: DispatchQueue, callback: @escaping (URLResult<Data>) -> Void)
+  func receive(on queue: DispatchQueue, callback: @escaping @Sendable (URLResult<Data>) -> Void)
 }
diff --git a/Sources/HTTPFluent/URLError.swift b/Sources/HTTPFluent/URLError.swift
index bd3716f..3119a46 100644
--- a/Sources/HTTPFluent/URLError.swift
+++ b/Sources/HTTPFluent/URLError.swift
@@ -3,11 +3,16 @@
 //  HTTPFluent
 //
 //  Created by Gregory Higley on 2020-02-24.
-//  Copyright © 2020 Prosumma. All rights reserved.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
 import Foundation
 
+#if canImport(FoundationNetworking)
+import FoundationNetworking
+#endif
+
 /// An error that may occur as a result of constructing or publishing a `URLRequest`.
 public enum URLError: Error {
   case error(Error?)
diff --git a/Sources/HTTPFluent/URLRequestBuilder.swift b/Sources/HTTPFluent/URLRequestBuilder.swift
index fde4cf6..54c1b85 100644
--- a/Sources/HTTPFluent/URLRequestBuilder.swift
+++ b/Sources/HTTPFluent/URLRequestBuilder.swift
@@ -3,19 +3,24 @@
 //  HTTPFluent
 //
 //  Created by Gregory Higley on 2020-05-08.
-//  Copyright © 2020 Prosumma. All rights reserved.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
 import Foundation
 
-public struct URLRequestBuilder {
+#if canImport(FoundationNetworking)
+import FoundationNetworking
+#endif
+
+public struct URLRequestBuilder: Sendable {
   public typealias Apply = (inout Self) -> Void
 
   fileprivate var error: URLError?
   fileprivate var components: URLComponents
   fileprivate var method: String = "GET"
   fileprivate var headers: [String: String] = [:]
-  fileprivate var body: (() throws -> Data)?
+  fileprivate var body: (@Sendable () throws -> Data)?
 
   private init(components: URLComponents) {
     self.components = components
@@ -104,7 +109,7 @@ extension URLRequestBuilder {
     }
   }
 
-  static func buildBody(_ body: @escaping () throws -> Data) -> URLRequestBuilder.Apply {
+  static func buildBody(_ body: @escaping @Sendable () throws -> Data) -> URLRequestBuilder.Apply {
     return { builder in
       builder.body = body
     }
diff --git a/Sources/HTTPFluent/URLRequestBuilderProtocol+HTTPBody.swift b/Sources/HTTPFluent/URLRequestBuilderProtocol+HTTPBody.swift
index c5f116c..871a00b 100644
--- a/Sources/HTTPFluent/URLRequestBuilderProtocol+HTTPBody.swift
+++ b/Sources/HTTPFluent/URLRequestBuilderProtocol+HTTPBody.swift
@@ -3,12 +3,17 @@
 //  HTTPFluent
 //
 //  Created by Gregory Higley on 2020-05-09.
-//  Copyright © 2020 Prosumma. All rights reserved.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
 import Combine
 import Foundation
 
+#if canImport(FoundationNetworking)
+import FoundationNetworking
+#endif
+
 public extension URLRequestBuilderProtocol {
   /**
    Low-level function to set the HTTP body.
@@ -16,7 +21,7 @@ public extension URLRequestBuilderProtocol {
    Don't use this. Use higher-level functions like `post(json:)`,
    which ultimately call this one.
    */
-  func body(_ body: @escaping () throws -> Data) -> Self {
+  func body(_ body: @escaping @Sendable () throws -> Data) -> Self {
     build(URLRequestBuilder.buildBody(body))
   }
   
@@ -25,13 +30,18 @@ public extension URLRequestBuilderProtocol {
     body { data }
   }
 
+  /// Send a `String` without setting an HTTP method.
+  func send(string: String, encoding: String.Encoding = .utf8) -> Self {
+    send(data: string.data(using: .utf8)!)
+  }
+
   /// Send `FormData` without setting an HTTP method.
   func send(form: FormData) -> Self {
     content(type: form.contentType).body { form.encoded() }
   }
 
   /// Encode a type in the HTTP body without setting an HTTP method.
-  func send<Request: Encodable, Encoder: TopLevelEncoder>(
+  func send<Request: Encodable & Sendable, Encoder: TopLevelEncoder & Sendable>(
     _ request: Request,
     encoder: Encoder
   ) -> Self where Encoder.Output == Data {
@@ -39,7 +49,7 @@ public extension URLRequestBuilderProtocol {
   }
 
   /// Send JSON in the HTTP body without setting an HTTP method.
-  func send<Request: Encodable>(json request: Request) -> Self {
+  func send<Request: Encodable & Sendable>(json request: Request) -> Self {
     send(request, encoder: JSONEncoder()).content(type: .json)
   }
 
@@ -48,13 +58,18 @@ public extension URLRequestBuilderProtocol {
     send(data: data).method(.post)
   }
 
+  /// Post a `String`
+  func post(string: String, encoding: String.Encoding = .utf8) -> Self {
+    send(string: string, encoding: encoding).method(.post)
+  }
+
   /// Post `FormData`
   func post(form: FormData) -> Self {
     send(form: form).method(.post)
   }
 
   /// Post `Request` encoded with `Encoder`
-  func post<Request: Encodable, Encoder: TopLevelEncoder>(
+  func post<Request: Encodable & Sendable, Encoder: TopLevelEncoder & Sendable>(
     _ request: Request,
     encoder: Encoder
   ) -> Self where Encoder.Output == Data {
@@ -62,7 +77,7 @@ public extension URLRequestBuilderProtocol {
   }
 
   /// Post `Request` encoded as JSON
-  func post<Request: Encodable>(json request: Request) -> Self {
+  func post<Request: Encodable & Sendable>(json request: Request) -> Self {
     send(json: request).method(.post)
   }
 
@@ -71,13 +86,18 @@ public extension URLRequestBuilderProtocol {
     send(data: data).method(.patch)
   }
 
+  /// Patch a `String`
+  func patch(string: String, encoding: String.Encoding = .utf8) -> Self {
+    send(string: string, encoding: encoding).method(.patch)
+  }
+
   /// Patch `FormData`
   func patch(form: FormData) -> Self {
     send(form: form).method(.patch)
   }
 
   /// Patch `Request` encoded with `Encoder`
-  func patch<Request: Encodable, Encoder: TopLevelEncoder>(
+  func patch<Request: Encodable & Sendable, Encoder: TopLevelEncoder & Sendable>(
     _ request: Request,
     encoder: Encoder
   ) -> Self where Encoder.Output == Data {
@@ -85,7 +105,7 @@ public extension URLRequestBuilderProtocol {
   }
 
   /// Patch `Request` encoded as JSON
-  func patch<Request: Encodable>(json request: Request) -> Self {
+  func patch<Request: Encodable & Sendable>(json request: Request) -> Self {
     send(json: request).method(.patch)
   }
 
@@ -94,13 +114,18 @@ public extension URLRequestBuilderProtocol {
     send(data: data).method(.put)
   }
 
+  /// Put a `String`
+  func put(string: String, encoding: String.Encoding = .utf8) -> Self {
+    send(string: string, encoding: encoding).method(.put)
+  }
+
   /// Put `FormData`
   func put(form: FormData) -> Self {
     send(form: form).method(.put)
   }
 
   /// Put `Request` encoded by `Encoder`
-  func put<Request: Encodable, Encoder: TopLevelEncoder>(
+  func put<Request: Encodable & Sendable, Encoder: TopLevelEncoder & Sendable>(
     _ request: Request,
     encoder: Encoder
   ) -> Self where Encoder.Output == Data {
@@ -108,7 +133,7 @@ public extension URLRequestBuilderProtocol {
   }
 
   /// Put `Request` encoded as JSON
-  func put<Request: Encodable>(json request: Request) -> Self {
+  func put<Request: Encodable & Sendable>(json request: Request) -> Self {
     send(json: request).method(.put)
   }
 }
diff --git a/Sources/HTTPFluent/URLRequestBuilderProtocol+URL.swift b/Sources/HTTPFluent/URLRequestBuilderProtocol+URL.swift
index 3be800c..5e6ecc7 100644
--- a/Sources/HTTPFluent/URLRequestBuilderProtocol+URL.swift
+++ b/Sources/HTTPFluent/URLRequestBuilderProtocol+URL.swift
@@ -3,7 +3,8 @@
 //  HTTPFluent
 //
 //  Created by Gregory Higley on 2020-05-08.
-//  Copyright © 2020 Prosumma. All rights reserved.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
 import Foundation
diff --git a/Sources/HTTPFluent/URLRequestBuilderProtocol+URLRequest.swift b/Sources/HTTPFluent/URLRequestBuilderProtocol+URLRequest.swift
index 0df3453..84aecd9 100644
--- a/Sources/HTTPFluent/URLRequestBuilderProtocol+URLRequest.swift
+++ b/Sources/HTTPFluent/URLRequestBuilderProtocol+URLRequest.swift
@@ -3,9 +3,11 @@
 //  HTTPFluent
 //
 //  Created by Gregory Higley on 2020-05-08.
-//  Copyright © 2020 Prosumma. All rights reserved.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
+import CoreFoundation
 import Foundation
 
 public extension URLRequestBuilderProtocol {
@@ -33,7 +35,8 @@ public extension URLRequestBuilderProtocol {
     var contentType: String = type.rawValue
     if let charset = charset {
       let enc = CFStringConvertNSStringEncodingToEncoding(charset.rawValue)
-      let iana = CFStringConvertEncodingToIANACharSetName(enc) as NSString as String
+      let cfiana: CFString = CFStringConvertEncodingToIANACharSetName(enc)
+      let iana = String(describing: cfiana)
       contentType += ";charset=\(iana)"
     }
     return header(contentType, forField: .contentType)
diff --git a/Sources/HTTPFluent/URLRequestBuilderProtocol.swift b/Sources/HTTPFluent/URLRequestBuilderProtocol.swift
index 0b37bb6..6bf9f55 100644
--- a/Sources/HTTPFluent/URLRequestBuilderProtocol.swift
+++ b/Sources/HTTPFluent/URLRequestBuilderProtocol.swift
@@ -3,11 +3,16 @@
 //  HTTPFluent
 //
 //  Created by Gregory Higley on 2020-05-08.
-//  Copyright © 2020 Prosumma. All rights reserved.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
 import Foundation
 
+#if canImport(FoundationNetworking)
+import FoundationNetworking
+#endif
+
 /// A conforming type may be used to build a `URLRequest`.
 public protocol URLRequestBuilderProtocol {
   /**
diff --git a/Sources/HTTPFluent/URLResult.swift b/Sources/HTTPFluent/URLResult.swift
index 6de8c01..565199d 100644
--- a/Sources/HTTPFluent/URLResult.swift
+++ b/Sources/HTTPFluent/URLResult.swift
@@ -3,8 +3,10 @@
 //  HTTPFluent
 //
 //  Created by Gregory Higley on 2020-08-02.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
 import Foundation
 
-public typealias URLResult<Success> = Result<Success, URLError>
+public typealias URLResult<Success: Sendable> = Result<Success, URLError>
diff --git a/Tests/HTTPFluentTests/Const.swift b/Tests/HTTPFluentTests/Const.swift
index d9bbbe6..e9b92e6 100644
--- a/Tests/HTTPFluentTests/Const.swift
+++ b/Tests/HTTPFluentTests/Const.swift
@@ -2,7 +2,9 @@
 //  Const.swift
 //  HTTPFluent
 //
-//  Created by Gregory Higley on 4/1/20.
+//  Created by Gregory Higley on 2020-04-01.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
 import HTTPFluent
diff --git a/Tests/HTTPFluentTests/HTTPBinResponse.swift b/Tests/HTTPFluentTests/HTTPBinResponse.swift
index 74f4c71..0113109 100644
--- a/Tests/HTTPFluentTests/HTTPBinResponse.swift
+++ b/Tests/HTTPFluentTests/HTTPBinResponse.swift
@@ -2,7 +2,9 @@
 //  HTTPBinResponse.swift
 //  HTTPFluent
 //
-//  Created by Gregory Higley on 4/2/20.
+//  Created by Gregory Higley on 2020-04-02.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
 import Foundation
diff --git a/Tests/HTTPFluentTests/HTTPFluentAsyncTests.swift b/Tests/HTTPFluentTests/HTTPFluentAsyncTests.swift
index 492d157..a606e49 100644
--- a/Tests/HTTPFluentTests/HTTPFluentAsyncTests.swift
+++ b/Tests/HTTPFluentTests/HTTPFluentAsyncTests.swift
@@ -2,24 +2,23 @@
 //  HTTPFluentAsyncTests.swift
 //  
 //
-//  Created by Gregory Higley on 12/25/21.
+//  Created by Gregory Higley on 2021-12-25.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
-#if canImport(Combine)
 import Combine
-#endif
-
-import XCTest
 import HTTPFluent
+import Testing
 
-#if swift(>=5.5)
-
-@available(macOS 12.0, iOS 15.0, tvOS 15.0, watchOS 8.0, *)
-class HTTPFluentAsyncTests: XCTestCase {
-  func testGetJSON() async throws {
+struct HTTPFluentAsyncTests {
+  @Test func testGetJSON() async throws {
     let slideshows = try await URLClient.bin.path("json").receive(json: Slideshows.self)
-    XCTAssertEqual(slideshows.slideshow.title, "Sample Slide Show")
+    #expect(slideshows.slideshow.title == "Sample Slide Show")
+  }
+  
+  @Test func testHeaders() async throws {
+    let response = try await URLClient.bin.path("headers").content(type: .json, charset: .utf8).receive(json: HTTPHeaderResponse.self)
+    #expect(response.headers["Content-Type"] == "application/json;charset=utf-8")
   }
 }
-
-#endif
diff --git a/Tests/HTTPFluentTests/HTTPFluentCombineTests.swift b/Tests/HTTPFluentTests/HTTPFluentCombineTests.swift
index ca1cb58..31cce67 100644
--- a/Tests/HTTPFluentTests/HTTPFluentCombineTests.swift
+++ b/Tests/HTTPFluentTests/HTTPFluentCombineTests.swift
@@ -1,10 +1,16 @@
-#if canImport(Combine)
+//
+//  HTTPFluentCombineTests.swift
+//  HTTPFluent
+//
+//  Created by Gregory Higley on 2020-04-01.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
+//
 
 import Combine
 import XCTest
 import HTTPFluent
 
-@available(macOS 10.15, iOS 13.0, tvOS 13.0, watchOS 6.0, *)
 func fulfill<E: Error>(_ e: XCTestExpectation, expectError: Bool = false) -> (Subscribers.Completion<E>) -> Void {
   return { c in
     if expectError {
@@ -21,7 +27,6 @@ func fulfill<E: Error>(_ e: XCTestExpectation, expectError: Bool = false) -> (Su
   }
 }
 
-@available(macOS 10.15, iOS 13.0, tvOS 13.0, watchOS 6.0, *)
 final class HttpFluentCombineTests: XCTestCase {
 
   func testGetJSON() {
@@ -31,7 +36,7 @@ final class HttpFluentCombineTests: XCTestCase {
     }
     let cancellable = URLClient.bin
       .path("json")
-      .publisher(json: Slideshows.self)
+      .receivePublisher(json: Slideshows.self)
       .sink(
         receiveCompletion: fulfill(e),
         receiveValue: print(slideshows:)
@@ -47,7 +52,7 @@ final class HttpFluentCombineTests: XCTestCase {
       .path("post")
       .post(json: slide)
       .accept(.json)
-      .publisher(decode: Decoders.string)
+      .receivePublisher(decode: Decoders.string)
       .sink(receiveCompletion: fulfill(e)) { s in
         print(s)
       }
@@ -62,7 +67,7 @@ final class HttpFluentCombineTests: XCTestCase {
       .path("status", statusCode)
       .accept(.json)
       .method(.put)
-      .publisher(decode: Decoders.string)
+      .receivePublisher(decode: Decoders.string)
       .sink(
         receiveCompletion: fulfill(e, expectError: true),
         receiveValue: { _ in XCTFail("Expected HTTP Status \(statusCode).") }
@@ -71,5 +76,3 @@ final class HttpFluentCombineTests: XCTestCase {
     cancellable.cancel()
   }
 }
-
-#endif
diff --git a/Tests/HTTPFluentTests/HTTPFluentReceiveTests.swift b/Tests/HTTPFluentTests/HTTPFluentReceiveTests.swift
index 440bfe2..03c5859 100644
--- a/Tests/HTTPFluentTests/HTTPFluentReceiveTests.swift
+++ b/Tests/HTTPFluentTests/HTTPFluentReceiveTests.swift
@@ -2,27 +2,22 @@
 //  HTTPFluentReceiveTests.swift
 //  HTTPFluentTests
 //
-//  Created by Gregory Higley on 8/12/20.
+//  Created by Gregory Higley on 2020-08-12.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
-import XCTest
 import HTTPFluent
+import Testing
 
-class HTTPFluentReceiveTests: XCTestCase {
-
-  func testGetJSON() {
-    let e = expectation(description: "http")
-    URLClient.bin
-      .path("json")
-      .receive(json: Slideshows.self) { result in
-        do {
-          try print(result.get())
-        } catch {
-          XCTFail("\(error)")
+struct HTTPFluentReceiveTests {
+  @Test func testGetJSON() async throws {
+    _ = try await withCheckedThrowingContinuation { cont in
+      URLClient.bin
+        .path("json")
+        .receive(json: Slideshows.self) { result in
+          cont.resume(with: result)
         }
-        e.fulfill()
-      }
-    wait(for: [e], timeout: 10)
+    }
   }
-  
-}
+}
\ No newline at end of file
diff --git a/Tests/HTTPFluentTests/HTTPHeaderResponse.swift b/Tests/HTTPFluentTests/HTTPHeaderResponse.swift
new file mode 100644
index 0000000..48eab1f
--- /dev/null
+++ b/Tests/HTTPFluentTests/HTTPHeaderResponse.swift
@@ -0,0 +1,14 @@
+//
+//  HTTPHeaderResponse.swift
+//  HTTPFluent
+//
+//  Created by Gregory Higley on 2023-03-24.
+//  Copyright © 2023 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
+//
+
+import Foundation
+
+struct HTTPHeaderResponse: Decodable {
+  let headers: [String: String]
+}
diff --git a/Tests/HTTPFluentTests/Slide.swift b/Tests/HTTPFluentTests/Slide.swift
index b234c92..74ad792 100644
--- a/Tests/HTTPFluentTests/Slide.swift
+++ b/Tests/HTTPFluentTests/Slide.swift
@@ -1,8 +1,10 @@
 //
-//  File.swift
-//  
+//  Slide.swift
+//  HTTPFluent
 //
-//  Created by Gregory Higley on 4/1/20.
+//  Created by Gregory Higley on 2020-04-01.
+//  Copyright © 2020 Prosumma.
+//  This code is licensed under the MIT license (see LICENSE for details).
 //
 
 struct Slide: Codable {