A server-side Swift implementation of the WebPush standard.
Add WebPush as a dependency in your Package.swift file to start using it. Then, add import WebPush to any file you wish to use the library in.
Please check the releases for recommended versions.
dependencies: [
.package(
url: "https://github.com/mochidev/swift-webpush.git",
.upToNextMinor(from: "0.3.3")
),
],
...
targets: [
.target(
name: "MyPackage",
dependencies: [
.product(name: "WebPush", package: "swift-webpush"),
...
]
),
.testTarget(
name: "MyPackageTests",
dependencies: [
.product(name: "WebPushTesting", package: "swift-webpush"),
...
]
),
]If you are unfamiliar with the WebPush standard, we suggest you first familiarize yourself with the following core concepts:
Subscriber
A Subscriber represents a device that has opted in to receive push messages from your service.
[!IMPORTANT] A subscriber should not be conflated with a user — a single user may be logged in on multiple devices, while a subscriber may be shared by multiple users on a single device. It is up to you to manage this complexity and ensure user information remains secure across session boundaries by registering, unregistering, and updating the subscriber when a user logs in or out.
Application Server
The Application Server is a server you run to manage subscriptions and send push notifications. The actual servers that perform these roles may be different, but they must all use the same VAPID keys to function correctly.
[!CAUTION] Using a VAPID key that wasn't registered with a subscription will result in push messages failing to reach their subscribers.
VAPID Key
VAPID, or Voluntary Application Server Identification, describes a standard for letting your application server introduce itself at time of subscription registration so that the subscription returned back to you may only be used by your service, and can't be shared with other unrelated services.
This is made possible by generating a VAPID key pair to represent your server with. At time of registration, the public key is shared with the browser, and the subscription that is returned is locked to this key. When sending a push message, the private key is used to identify your application server to the push service so that it knows who you are before forwarding messages to subscribers.
[!CAUTION] It is important to note that you should strive to use the same key for as long as possible for a given subscriber — you won't be able to send messages to existing subscribers if you ever regenerate this key, so keep it secure!
Push Service
A Push Service is run by browsers to coordinate delivery of messages to subscribers on your behalf.
Before integrating WebPush into your server, you must generate one time VAPID keys to identify your server to push services with. To help we this, we provide vapid-key-generator, which you can install and use as needed:
% git clone https://github.com/mochidev/swift-webpush.git
% cd swift-webpush/vapid-key-generator
% swift package experimental-installTo uninstall the generator:
% swift package experimental-uninstall vapid-key-generatorTo update the generator, uninstall it and re-install it after pulling from main:
% swift package experimental-uninstall vapid-key-generator
% swift package experimental-installOnce installed, a new configuration can be generated as needed. Here, we generate a configuration with https://example.com as our support URL for push service administrators to use to contact us when issues occur:
% ~/.swiftpm/bin/vapid-key-generator https://example.com
VAPID.Configuration: {"contactInformation":"https://example.com","expirationDuration":79200,"primaryKey":"6PSSAJiMj7uOvtE4ymNo5GWcZbT226c5KlV6c+8fx5g=","validityDuration":72000}
Example Usage:
// TODO: Load this data from .env or from file system
let configurationData = Data(#" {"contactInformation":"https://example.com","expirationDuration":79200,"primaryKey":"6PSSAJiMj7uOvtE4ymNo5GWcZbT226c5KlV6c+8fx5g=","validityDuration":72000} "#.utf8)
let vapidConfiguration = try JSONDecoder().decode(VAPID.Configuration.self, from: configurationData)
Once generated, the configuration JSON should be added to your deployment's .env and kept secure so it can be accessed at runtime by your application server, and only by your application server. Make sure this key does not leak and is not stored alongside subscriber information.
Note
You can specify either a support URL or an email for administrators of push services to contact you with if problems are encountered, or you can generate keys only if you prefer to configure contact information at runtime:
% ~/.swiftpm/bin/vapid-key-generator -h
OVERVIEW: Generate VAPID Keys.
Generates VAPID keys and configurations suitable for use on your server. Keys should generally only be generated once
and kept secure.
USAGE: vapid-key-generator <support-url>
vapid-key-generator --email <email>
vapid-key-generator --key-only
ARGUMENTS:
<support-url> The fully-qualified HTTPS support URL administrators of push services may contact you at:
https://example.com/support
OPTIONS:
-k, --key-only Only generate a VAPID key.
-s, --silent Output raw JSON only so this tool can be piped with others in scripts.
-p, --pretty Output JSON with spacing. Has no effect when generating keys only.
--email <email> Parse the input as an email address.
-h, --help Show help information.Important
If you only need to change the contact information, you can do so in the JSON directly — a key should not be regenerated when doing this as it will invalidate all existing subscriptions.
Tip
If you prefer, you can also generate keys in your own code by calling VAPID.Key(), but remember, the key should be persisted and re-used from that point forward!
During the setup stage of your application server, decode the VAPID configuration you created above and initialize a WebPushManager with it:
import WebPush
...
guard
let rawVAPIDConfiguration = ProcessInfo.processInfo.environment["VAPID-CONFIG"],
let vapidConfiguration = try? JSONDecoder().decode(VAPID.Configuration.self, from: Data(rawVAPIDConfiguration.utf8))
else { fatalError("VAPID keys are unavailable, please generate one and add it to the environment.") }
let manager = WebPushManager(
vapidConfiguration: vapidConfiguration,
backgroundActivityLogger: logger
/// If you customized the event loop group your app uses, you can set it here:
// eventLoopGroupProvider: .shared(app.eventLoopGroup)
)
try await ServiceGroup(
services: [
/// Your other services here
manager
],
gracefulShutdownSignals: [.sigint],
logger: logger
).run()If you are not yet using Swift Service Lifecycle, you can skip adding it to the service group, and it'll shut down on deinit instead. This however may be too late to finish sending over all in-flight messages, so prefer to use a ServiceGroup for all your services if you can.
You'll also want to serve a serviceWorker.mjs file at the root of your server (it can be anywhere, but there are scoping restrictions that are simplified by serving it at the root) to handle incoming notifications:
self.addEventListener('push', function(event) {
const data = event.data?.json() ?? {};
event.waitUntil((async () => {
/// Try parsing the data, otherwise use fallback content. DO NOT skip sending the notification, as you must display one for every push message that is received or your subscription will be dropped.
let title = data?.title ?? "Your App Name";
const body = data?.body ?? "New Content Available!";
await self.registration.showNotification(title, {
body,
icon: "/notification-icon.png", /// Only some browsers support this.
data
});
})());
});Note
.mjs here allows your code to import other js modules as needed. If you are not using Vapor, please make sure your server uses the correct mime type for this file extension.
To register a subscriber, you'll need backend code to provide your VAPID key, and frontend code to ask the browser for a subscription on behalf of the user.
On the backend (we are assuming Vapor here), register a route that returns your VAPID public key:
import WebPush
...
/// Listen somewhere for a VAPID key request. This path can be anything you want, and should be available to all parties you with to serve push messages to.
app.get("vapidKey", use: loadVapidKey)
...
/// A wrapper for the VAPID key that Vapor can encode.
struct WebPushOptions: Codable, Content, Hashable, Sendable {
static let defaultContentType = HTTPMediaType(type: "application", subType: "webpush-options+json")
var vapid: VAPID.Key.ID
}
/// The route handler, usually part of a route controller.
@Sendable func loadVapidKey(request: Request) async throws -> WebPushOptions {
WebPushOptions(vapid: manager.nextVAPIDKeyID)
}Also register a route for persisting Subscriber's:
import WebPush
...
/// Listen somewhere for new registrations. This path can be anything you want, and should be available to all parties you with to serve push messages to.
app.get("registerSubscription", use: registerSubscription)
...
/// A custom type for communicating the status of your subscription. Fill this out with any options you'd like to communicate back to the user.
struct SubscriptionStatus: Codable, Content, Hashable, Sendable {
var subscribed = true
}
/// The route handler, usually part of a route controller.
@Sendable func registerSubscription(request: Request) async throws -> SubscriptionStatus {
let subscriptionRequest = try request.content.decode(Subscriber.self, as: .jsonAPI)
// TODO: Persist subscriptionRequest!
return SubscriptionStatus()
}Note
WebPushManager (manager here) is fully sendable, and should be shared with your controllers using dependency injection. This allows you to fully test your application server by relying on the provided WebPushTesting library in your unit tests to mock keys, verify delivery, and simulate errors.
On the frontend, register your service worker, fetch your vapid key, and subscribe on behalf of the user:
const serviceRegistration = await navigator.serviceWorker?.register("/serviceWorker.mjs", { type: "module" });
let subscription = await registration?.pushManager?.getSubscription();
/// Wait for the user to interact with the page to request a subscription.
document.getElementById("notificationsSwitch").addEventListener("click", async ({ currentTarget }) => {
try {
/// If we couldn't load a subscription, now's the time to ask for one.
if (!subscription) {
const applicationServerKey = await loadVAPIDKey();
subscription = await serviceRegistration.pushManager.subscribe({
userVisibleOnly: true,
applicationServerKey,
});
}
/// It is safe to re-register the same subscription.
const subscriptionStatusResponse = await registerSubscription(subscription);
/// Do something with your registration. Some may use it to store notification settings and display those back to the user.
...
} catch (error) {
/// Tell the user something went wrong here.
console.error(error);
}
}
});
...
async function loadVAPIDKey() {
/// Make sure this is the same route used above.
const httpResponse = await fetch(`/vapidKey`);
const webPushOptions = await httpResponse.json();
if (httpResponse.status != 200) throw new Error(webPushOptions.reason);
return webPushOptions.vapid;
}
export async function registerSubscription(subscription) {
/// Make sure this is the same route used above.
const subscriptionStatusResponse = await fetch(`/registerSubscription`, {
method: "POST",
body: {
...subscription.toJSON(),
/// It is good practice to provide the applicationServerKey back here so we can track which one was used if multiple were provided during configuration.
applicationServerKey: subscription.options.applicationServerKey,
}
});
/// Do something with your registration. Some may use it to store notification settings and display those back to the user.
...
}To send a message, call one of the send() methods on WebPushManager with a Subscriber:
import WebPush
...
do {
try await manager.send(
json: ["title": "Test Notification", "body": "Hello, World!"
/// If sent from a request, pass the request's logger here to maintain its metadata.
// logger: request.logger
)
} catch BadSubscriberError() {
/// The subscription is no longer valid and should be removed.
} catch MessageTooLargeError() {
/// The message was too long and should be shortened.
} catch let error as HTTPError {
/// The push service ran into trouble. error.response may help here.
} catch {
/// An unknown error occurred.
}Your service worker will receive this message, decode it, and present it to the user.
Note
Although the spec supports it, most browsers do not support silent notifications, and will drop a subscription if they are used.
The WebPushTesting module can be used to obtain a mocked WebPushManager instance that allows you to capture all messages that are sent out, or throw your own errors to validate your code functions appropriately. Only import WebPushTesting in your testing targets.
Contribution is welcome! Please take a look at the issues already available, or start a new discussion to propose a new feature. Although guarantees can't be made regarding feature requests, PRs that fit within the goals of the project and that have been discussed beforehand are more than welcome!
Please make sure that all submissions have clean commit histories, are well documented, and thoroughly tested. Please rebase your PR before submission rather than merge in main. Linear histories are required, so merge commits in PRs will not be accepted.
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