Description
WhoKnew Signal sends real push notifications directly from your WordPress site to every major browser – including iPhone and iPad – with no SaaS account, no Firebase, and no monthly subscription. One plugin. Completely yours.
Unlimited Subscribers in the Free Plugin
Grow your list without hitting a subscriber cap. Unlimited active subscribers are included in the free plugin – not a trial, not a temporary unlock, and not tied to a paid upgrade. Many WordPress push plugins and SaaS tools charge when your list grows (subscriber limits, paid tiers, or per-seat pricing). WhoKnew Signal stores every endpoint in your WordPress database and does not count subscribers against a paid quota.
- Unlimited subscribers (free) – 10, 1,000, or 100,000+ active subscribers on the same free plugin
- No per-subscriber fees – your hosting plan is the practical limit, not an artificial plugin cap
- Pro adds automation – Install on Phones, background sends, WooCommerce, analytics, and more (not a higher subscriber limit)
One Plugin That Does What Two Used to Require
Until now, getting iOS push notifications working on WordPress required two separate plugins: a PWA plugin (to set up your web app manifest and home screen icon) and a push notification plugin (to actually send the notifications). Then you had to make them work together.
WhoKnew Signal does both in a single, lightweight plugin.
The built-in Web App tab handles what standalone PWA plugins do: your manifest.json, app icon, theme color, display mode, and Apple touch icon meta tags. Visitors can add your site to their home screen manually; WhoKnew Signal Pro adds the [wkspn_install_buttons] shortcode for guided Android and iOS install buttons. Once installed as a PWA, visitors can receive push notifications on supported browsers.
If you have Super PWA, PWA for WP, or a similar plugin installed just to get iOS push working – you can replace it with WhoKnew Signal alone.
Self-Hosted Web Push on Your WordPress Server
WhoKnew Signal is built for site owners who want truly self-hosted web push notifications and a PWA (Progressive Web App) setup without a SaaS dashboard, without Firebase as your subscriber database, and without per-subscriber monthly fees.
Many WordPress push plugins route campaigns through a vendor API or store tokens off-site. SaaS tools like OneSignal and PushEngage are upfront about that model. WhoKnew Signal takes a different approach: subscriber endpoints live in your WordPress database, and campaigns are sent from your server using the open VAPID Web Push standard.
- Unlimited subscribers on free – no 250- or 2,000-subscriber paywall common in other push plugins
- VAPID web push – supported in Chrome, Firefox, Edge, Android, and Safari (including iOS when your site is installed to the home screen as a PWA)
- Subscriber data on your server – push tokens stay in your database; WhoKnew does not host your list
- Direct delivery from WordPress – your site sends encrypted payloads to each browser’s push endpoint (see External services below for FCM, Mozilla, and Apple delivery networks)
- Built-in PWA manifest – app name, icons, theme color, display mode, and Apple touch icon meta tags without a separate PWA plugin
- No WhoKnew account required for the free plugin – no license server, analytics phone-home, or vendor relay for sending
WhoKnew Signal Pro (sold separately at whoknew.io) adds Install on Phones, background campaign sends, rich images, WooCommerce automation, segmentation, analytics, scheduling, and optional SMS notifications via your own Twilio account.
Subscriptions That Actually Stay Subscribed
Most push notification plugins lose a subscriber the moment they clear their browser cache. WhoKnew Signal is built differently:
- Survives browser cache clears – subscriber status is stored in both a cookie and browser storage. If one is wiped, the other picks it up automatically. No popup re-appears, no duplicate entry.
- Self-healing subscriptions – if both are cleared but the browser still holds the push subscription, the plugin silently re-registers in the background on the next visit. The subscriber never sees a popup again. They just stay subscribed.
- No Firebase account required – subscription persistence uses your site storage, not a Google developer project for your subscriber list
Once someone subscribes, WhoKnew Signal is designed to keep them subscribed across cache clears without storing your audience on a third-party push SaaS.
Post Types
- Free – auto-send on publish for blog posts (unlimited subscribers)
- Pro – auto-send for additional public post types such as pages, WooCommerce products, events, and custom post types from other plugins
Free Features
- Unlimited active subscribers – no subscriber cap in the free plugin (a major difference from capped free tiers elsewhere)
- Truly self-hosted – subscriber data stored only in your WordPress database
- Works on Chrome, Firefox, Edge, Android, macOS Safari, iOS Safari (via PWA)
- iOS and macOS Safari included free – no upgrade, no extra fee
- Built-in PWA / Web App manifest – replaces Super PWA and similar plugins
- Auto-send on publish for blog posts (additional post types in Pro)
- App name, icons, theme color, display mode, and start URL – all configurable
- VAPID keys auto-generated on activation – no setup, no accounts
- Beautiful soft-ask subscription popup (fully customizable text and colors)
- Welcome notification sent automatically the moment someone subscribes
- Auto-send notification when a blog post is published (more post types in Pro)
- Manual campaign send from the admin dashboard
- Manual and auto-send campaigns (blocking in-tab send; Pro adds background queue)
- Multiple campaigns can send at the same time (default: up to 5 concurrent sends)
- Live send progress in the admin (Send Dock on Signal tabs and admin bar badge)
- Subscriber management with browser and platform tracking
- Campaign history with click tracking
- VAPID key backup and restore – migrate to a new server without losing subscribers
- Privacy-minded – self-hosted data, browser consent, copy-paste privacy policy text in Settings; optional link to WordPress account when logged in
- No WhoKnew SaaS account – the free plugin does not phone home; push delivery uses browser networks documented under External services
Pro Features (whoknew.io)
- Install on Phones shortcode and settings
- Background campaign sends (leave the admin tab)
- Rich notification banner images
- WooCommerce push notifications – order updates and abandoned cart to linked accounts; broadcasts for new products, back in stock, and price drops
- Advanced analytics dashboard with subscriber growth, browser breakdown, and best send time
- Smart subscriber segments – engagement, device, tenure, and Woo purchase behavior (combine when sending)
- A/B test two notification variants with automatic winner promotion
- Action buttons – clickable call-to-action on every notification
- Scheduled campaigns – send at a future date and time
- Background send performance profiles – tune concurrency for shared, VPS, or cloud hosting (Settings tab)
- Welcome drip sequence – automated onboarding for new subscribers
- Re-engagement campaigns – automatically re-engage inactive subscribers
- Rich notifications with large images
- UTM tracking – measure push traffic in Google Analytics
- TTL control – expire stale notifications automatically
- Subscriber import & export – full server migration support
- SMS notifications (optional) – send text messages via your own Twilio account; subscriber phone numbers stored on your server, no SaaS markup
- Priority support
How It Compares
Typical setup models for WordPress push (your experience may vary by vendor):
Unlimited subscribers on free plan
* Vendor-hosted push plugins: Often capped (e.g. 250-2,000)
* SaaS (OneSignal etc.): Tier / usage limits
* WhoKnew Signal: Unlimited (free)
Subscriber list stored on your WordPress server
* Vendor-hosted push plugins: Often no
* SaaS (OneSignal etc.): No
* WhoKnew Signal: Yes
Send from your WordPress server (VAPID)
* Vendor-hosted push plugins: Often no
* SaaS (OneSignal etc.): No
* WhoKnew Signal: Yes
Requires vendor SaaS account to operate
* Vendor-hosted push plugins: Often yes
* SaaS (OneSignal etc.): Yes
* WhoKnew Signal: No (free plugin)
iOS / Safari web push (PWA)
* Vendor-hosted push plugins: Often paid add-on
* SaaS (OneSignal etc.): Paid tiers
* WhoKnew Signal: Included in free
Built-in PWA manifest
* Vendor-hosted push plugins: No
* SaaS (OneSignal etc.): No
* WhoKnew Signal: Yes
Install buttons shortcode (iOS + Android)
* Vendor-hosted push plugins: No
* SaaS (OneSignal etc.): No
* WhoKnew Signal: Yes (Pro)
SMS notifications
* Vendor-hosted push plugins: No
* SaaS (OneSignal etc.): Yes (managed SaaS)
* WhoKnew Signal: Optional — BYO-Twilio (Pro)
Welcome notification
* Vendor-hosted push plugins: Paid
* SaaS (OneSignal etc.): Paid
* WhoKnew Signal: Free
Discover all post types in UI
* Vendor-hosted push plugins: No (manual)
* SaaS (OneSignal etc.): Yes
* WhoKnew Signal: Yes
Auto-send all post types
* Vendor-hosted push plugins: No
* SaaS (OneSignal etc.): Posts only
* WhoKnew Signal: Yes
Price
* Vendor-hosted push plugins: $50/yr+
* SaaS (OneSignal etc.): $19 – 228+/yr
* WhoKnew Signal: Free / $80/yr Pro
Technical Notes
WhoKnew Signal uses the Web Push Protocol (RFC 8030), VAPID authentication (RFC 8292), and AES-128-GCM payload encryption (RFC 8291) – all implemented using PHP’s built-in OpenSSL functions. No external library, no Composer dependency.
The service worker is served via a WordPress query var (/?wkspn_sw=1) intercepted at init priority 1 with a Service-Worker-Allowed: / header, giving it origin-wide scope without placing any file in your web root. Compatible with all hosting environments including managed WordPress hosts.
Requirements
- WordPress 5.8 or higher
- PHP 7.4 or higher with OpenSSL extension
- HTTPS (SSL) – required by all browsers for Web Push
Privacy & Data
What WhoKnew Signal stores
WhoKnew Signal stores the following data only in your own WordPress database — nothing is ever sent to WhoKnew or any third-party server:
- Push subscription endpoint — an opaque URL generated by the visitor’s browser and their browser’s push delivery service (Google, Mozilla, or Apple). It cannot be traced back to an individual without access to their device.
- Browser name — e.g. Chrome, Firefox, Safari (detected from the user agent at subscription time).
- Platform — e.g. Windows, macOS, Android, iOS (detected from the user agent at subscription time).
- Subscription timestamp — the date and time the visitor subscribed.
- WordPress user ID (optional) — when the visitor is logged in, the subscription may be linked to their existing WordPress account on your site so account-related notifications (e.g. order updates with Pro) can reach that browser. The plugin does not store their name or email; it uses an account reference your site already has.
- Fail count and status — internal delivery health tracking.
- Click events (Pro) — click timestamps tied to the subscription endpoint for analytics and smart segments, not a separate marketing profile.
What WhoKnew Signal does NOT store
- No name or email address collected by this plugin for push subscriptions.
- No IP address stored for push subscriptions.
- No separate browsing history or off-site behavioral tracking.
- No subscriber push data transmitted to WhoKnew or any external analytics service.
Cookies and local storage
WhoKnew Signal sets one cookie and one localStorage key on the visitor’s browser:
wkspn_dismissed(cookie, expires after 30 days by default) — remembers that the visitor dismissed or responded to the push notification permission prompt, so it does not reappear on every page load. This is strictly necessary for the plugin to function correctly.wkspn_subscribed(localStorage) — remembers the visitor’s subscription state across page loads and cache clears so subscribed visitors are never shown the prompt again. This is strictly necessary for the plugin to function correctly.
Neither item contains personal data. Both are classified as strictly necessary by all major GDPR cookie consent plugins. WhoKnew Signal automatically registers these with Complianz, CookieYes, Cookiebot, Cookie Notice by dFactory, and GDPR Cookie Consent by WebToffee — they will never be blocked by a “necessary cookies only” consent choice.
Site owner responsibilities
As the operator of your WordPress site, you are the data controller for any subscriber data collected. You should disclose WhoKnew Signal’s data collection in your site’s privacy policy. The following paragraph may be copied and adapted (the same text appears in Settings):
This site uses WhoKnew Signal(TM) to deliver web push notifications. When you choose to subscribe, your browser generates a unique, opaque subscription token (a push endpoint URL) stored only in our database on this server. No third party receives or processes that token. We also record browser type, device platform (e.g. Windows, macOS, Android, iOS), and the date you subscribed. This plugin does not collect your name, email address, or IP address for push subscriptions. If you are logged in when you subscribe, we may link that browser token to your existing WordPress account on this site so account-related notifications (such as order updates) can reach this device. That uses an account reference your site already holds; the plugin does not gather additional identity information. Your subscription data is never sold or shared with external parties for marketing.
Your subscription is voluntary and based on consent through your browser permission prompt. You may withdraw consent at any time by removing notification permissions for this site in your browser settings (locate [your site URL]). Logging out on this browser removes the link between the subscription and your WordPress account on this device; revoking browser notification permission stops delivery. For subscriptions that were never linked to an account, we cannot match push records to you by name or email alone. Withdrawal does not affect the lawfulness of notifications sent before you withdrew.
External services
Push delivery uses the Web Push protocol (VAPID). When you send a notification, your WordPress server contacts each subscriber’s browser push endpoint. Depending on the browser, that endpoint may be operated by:
- Google Firebase Cloud Messaging (FCM) — Chrome, Edge, and most Android browsers. Terms: https://firebase.google.com/terms/ — Privacy: https://firebase.google.com/support/privacy
- Mozilla autopush — Firefox. Privacy: https://www.mozilla.org/privacy/
- Apple Push Notification service — Safari and iOS PWA subscribers. Privacy: https://www.apple.com/legal/privacy/
WhoKnew Signal does not require you to create accounts with these providers. Your subscriber list stays in your WordPress database; only the encrypted notification payload and endpoint URL are transmitted at send time.
WhoKnew Terms and Privacy Policy
WhoKnew Signal is published by WhoKnew. Use of WhoKnew websites, Pro licenses, support, and related services is governed by:
- Terms of Service: https://whoknew.io/terms/
- Privacy Policy: https://whoknew.io/privacy/
Purchasing or activating WhoKnew Signal Pro requires agreement to these terms. The free plugin does not send subscriber push data to WhoKnew; see the sections above for what is stored on your server and what site owners should disclose to their visitors.
Screenshots
Installation
- Upload the
whoknew-signal-push-notificationsfolder to/wp-content/plugins/ - Activate the plugin through the Plugins menu in WordPress
- Go to WhoKnew > WhoKnew Signal to configure settings
- VAPID keys are generated automatically – nothing to set up
- Visit the Web App tab to configure your PWA icon and colors (Pro: copy the install buttons shortcode from Install on Phones)
- The subscription popup appears to frontend visitors after your configured delay
FAQ
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Does this replace Super PWA, PWA for WP, or other PWA plugins?
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For most sites, yes. WhoKnew Signal includes a Web App tab that generates and serves your
manifest.json, configures your app icon, theme color, display mode, and injects required meta tags. Install on Phones ([wkspn_install_buttons]) is included in Pro for smart install buttons on Android and a guided iOS walkthrough. If your only reason for a separate PWA plugin was the manifest or iOS push setup, you can often use WhoKnew Signal alone.If you are using a separate PWA plugin only for advanced offline caching strategies beyond Signal’s built-in network-first caching, you may keep both – they will not conflict.
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Does this work on iOS?
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Yes. iOS Safari 16.4+ supports Web Push when the site is installed to the Home Screen as a Progressive Web App (PWA). WhoKnew Signal configures everything required: the web app manifest, the Apple touch icon, and the meta tags that tell iOS how to display your site when installed.
To receive push notifications on iPhone or iPad: open your install page in Safari (use the Install on Phones shortcode or share manual steps), tap Add to Home Screen, open the installed app once, then grant notification permission. From that point on, they receive push notifications exactly like a native app. iOS support is included in the free version at no extra charge.
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Why can’t I just use Chrome on iPhone?
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Chrome on iOS uses Apple’s WebKit rendering engine, not Chromium. Apple requires all iOS browsers to use WebKit, which means Chrome on iOS does not support Web Push. This is an Apple platform limitation that applies to every push notification plugin. The only way to receive push on iOS is through Safari with the site installed as a PWA.
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Do I need Firebase, OneSignal, or any external service?
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No. WhoKnew Signal sends directly from your WordPress server to the browser’s delivery network – Chrome uses Google’s FCM, Firefox uses Mozilla’s relay, Safari uses Apple’s push service. These are free delivery pipes that every browser already uses. You do not pay for them, sign up for them, or store any data on them. Your subscriber list lives entirely on your server.
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Does the free version make any calls to external servers?
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No. The free plugin operates entirely between your WordPress server and your visitors’ browsers. It does not phone home, send analytics, contact a license server, or make any external API calls. The only outbound connections it makes are the push notification deliveries themselves – sent directly from your server to the browser’s push delivery network. No WhoKnew server is ever involved.
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Can I migrate my subscribers to a new server or domain?
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Yes. Because subscriber endpoints are stored on your WordPress server (not on a push SaaS), you can migrate with WhoKnew Signal:
- Export your VAPID keys (Settings > Backup & Migration > Export Key Backup)
- Export your push subscribers (Settings > Backup & Migration > Download CSV – Pro feature)
- Install WhoKnew Signal on the new server and restore the VAPID key backup before any visitors load the page
- Import the push subscriber CSV (Settings > Backup & Migration > Import)
Your existing subscribers will continue receiving notifications without re-subscribing. This even works across domain changes.
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Can I migrate subscribers from another push plugin (OneSignal, magazine3, etc.)?
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Yes — and it happens automatically, with no effort from you or your visitors.
Switching push plugins normally means losing your subscriber list. Visitors who already granted permission to the old plugin can never be shown a native browser permission prompt again, so they silently disappear and cannot re-subscribe.
WhoKnew Signal detects this situation automatically. When a returning visitor has an active push subscription that belongs to a different plugin or service, WhoKnew Signal silently cancels that old subscription in the browser, then displays its own soft-ask popup. In most cases the browser already has permission granted and re-subscribes without a native dialog — the visitor simply clicks “Allow Notifications” on the WhoKnew popup and they are re-enrolled instantly. In some cases (for example if the browser reset the permission in the background, or on certain mobile Chrome versions) a brief native confirmation may still appear, but the visitor is never asked to grant permission from scratch.
This works for any service using the VAPID web push standard: OneSignal, Push Notifications for WordPress by magazine3, PushEngage, and others. Visitors who were never subscribed to any push service see the normal two-step popup flow (soft-ask, then native browser prompt) on their first visit. Existing WhoKnew Signal subscribers are never affected.
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Does it work with WooCommerce?
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The free plugin discovers WooCommerce and other public post types in Settings; auto-send on publish is included for blog posts. WhoKnew Signal Pro unlocks auto-send for products and other post types, plus WooCommerce automation: order notifications to linked WordPress accounts (processing, completed, refund), abandoned cart recovery, and broadcast triggers for new products, back in stock, and price drops.
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Why do subscriptions survive browser cache clears?
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When a visitor subscribes, WhoKnew Signal stores their subscription status in both a browser cookie and
localStorage. If the cache is cleared, whichever storage survives picks up immediately. If both are cleared but the browser’s underlying push subscription is still active, the plugin silently re-registers the subscriber in the background on their next visit. No popup re-appears, no duplicate entry is created. -
Is there a subscriber limit on the free plugin?
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No. The free plugin includes unlimited active subscribers. There is no 250-subscriber cap, no trial expiration on your list size, and no requirement to upgrade just to keep accepting new subscriptions. Upgrade to Pro when you want growth tools (Install on Phones, background sends, WooCommerce automation, segmentation, analytics, scheduling) – not because your audience outgrew a free quota.
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Is the free version really fully functional?
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Yes. The free version sends real push notifications to unlimited subscribers across supported browsers. The PWA manifest, welcome notification, auto-send on blog posts, and manual campaigns are included. Pro adds Install on Phones, background sends, rich images, additional post types, and the advanced features listed above. Very large broadcasts on shared hosting may need Pro background sending or a higher PHP time limit per request (see below).
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Unlimited subscribers does not mean unlimited time in a single PHP request. On the free plan, each campaign runs in one server request while you keep the admin page open. Many shared hosts limit PHP to 30-60 seconds; sends above a few hundred subscribers may be cut off by your server. WhoKnew Signal Pro sends in background batches (many short runs) so delivery is not tied to one long request. You can also ask your host to raise max_execution_time, which may help on Free but you must still wait on the page until sending finishes.
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What is the difference between Free and Pro for sending?
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Free delivers campaigns synchronously in the current browser request (fast for smaller lists). Pro can use instant send for lists below your Instant send threshold (Settings -> Background Send Performance) and background batched delivery for larger lists, with tunable batch size, parallelism, and time budget for your host.
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Does this comply with GDPR?
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WhoKnew Signal is built for privacy-conscious sites: subscriber data stays on your server, visitors consent via the browser permission prompt, and the plugin registers strictly necessary cookies with major consent tools (Complianz, Cookiebot, CookieYes, and others). The plugin does not collect names, email addresses, or IP addresses for push subscriptions. Each subscriber is stored as an opaque browser-generated endpoint plus browser type, platform, and subscription date. If a visitor is logged in, that endpoint may be linked to their existing WordPress account on your site (a reference your site already holds) so account-related notifications can reach the right device. Settings includes copy-paste privacy policy text for your site. You remain the data controller and should adapt that text to your practices.
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Contributors & Developers
“WhoKnew Signal – Self-Hosted Web Push Notifications & PWA” is open source software. The following people have contributed to this plugin.
Contributors
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Changelog
2.0.0
- Initial public release.
- WordPress.org compliance: Pro feature backend moved to Pro plugin; upsell UI only in free.
- Fixed sanitization for settings and PWA save filters; removed inline admin scripts.