Like many devs, I kept running into the same problem — monetizing my apps often felt like it took longer than building them.
I had a PHP setup for iOS validation that worked, but every new app meant more servers, databases, hosting costs, ongoing maintenance, and rebuilding purchase flows and subscription screens. For Android, I didn't even have a server-side validation option — I just had to trust the billing library response client-side, with no way to detect refunds or verify anything independently.
So I decided to tackle it properly and built my own monetization system.
I figured others in the B4X community were probably hitting the same walls, so what started as a simple solution for my own apps turned into months of building both the B4X library and the backend infrastructure behind it — into a service any B4X developer can use.
Register your app, grab your API key, add the b4xlib, and you're ready to go in just a few lines of code:
Check status anytime — instant, from local cache:
Key Features
• Built-in purchase and subscription screens (dark mode, theming, feature cards)
• Server-side validation — receipts verified directly with Apple and Google
• Zero secrets in your app — credentials stored securely server-side
• Smart caching — status checks are instant from local cache, background re-validation only when needed
• Restore purchases flow for both platforms
• Consumable product support
• Auto-generated privacy policy and terms of service (or supply your own URL/HTML)
• Subscription screens include Apple-required disclosures (auto-renewal terms, ToS/Privacy links) — App Store ready out of the box
• Non-purchasing users generate zero API calls
How It Works
1. Create an account at b4xpurchasemanager.com and register your app
2. Upload your store credentials (Apple Shared Secret / Google Play service account)
3. Grab your API key from the dashboard
4. Add the b4xlib to your project and initialize
5. The library handles everything — purchase UI, store interaction, receipt validation, caching, and status management
Your app talks to the BPM validation server over HTTPS. The server verifies receipts directly with Apple/Google and returns the result. No secrets in your app, no server to maintain.
Setup
1. Copy B4XPurchaseManager.b4xlib to your B4X Additional Libraries folder
2. iOS: Your provisioning profile must be based on an explicit App ID (e.g., com.yourcompany.yourapp) — wildcard profiles (com.*) will not compile
3. Android: Add the following to your manifest:
Add your constants to Class_Globals:
In-App Purchase Example (One-Time Unlock)
Subscription Example (Monthly + Yearly)
Additional Features
Caching & Validation
The library uses smart caching so status checks are always instant. In-app purchases and subscriptions are cached independently — only the type whose cache has expired gets re-validated:
• New in-app purchases (first 14 days / refund window): re-validated every 24 hours
• Established in-app purchases (after 14 days): re-validated every 14 days (~2 credits/month)
• Active subscriptions: re-validated every 24 hours (~30 credits/month)
• Expired subscriptions: go dormant after 7-day grace period (zero cost)
• Refunded purchases: go dormant immediately (zero cost)
• Users who never purchased: zero API calls, zero credits consumed
CheckStatus reads from local cache instantly. Background validation only triggers when cache expires. Blended average: ~15 validations per paying user per month.
Pricing
1 credit = 1 validation. Free tier: 500 credits/month (no credit card required). Paid tiers start at $5/month.
You only pay for active paying users — non-purchasers, expired subs, and refunded users all cost zero.
Validation typically costs less than 1% of what your paying users generate in revenue.
METHODS REFERENCE:
PROPERTIES REFERENCE:
Links
• Website & Docs: https://b4xpurchasemanager.com
• Dashboard: https://app.b4xpurchasemanager.com
Step-by-step guides for Android setup, iOS setup, Google Play service account, Apple Shared Secret, and more are available on the website — along with a detailed FAQ.
v1.01 Added auto-restore: automatically checks store for existing purchases on first launch (new device, reinstall, migration)
v1.02 Added AdvancedDebugMode: logs exactly what the store returned when products don't show up — the IDs requested, what came back, and what didn't.
Added AutoInappValidation: by default, in-app purchases only re-validate for the first 21 days (covering the refund window), then stop — you re-validate later via ValidateNow. Turn this on to keep auto-validating every 14 days indefinitely for extra coverage.
I had a PHP setup for iOS validation that worked, but every new app meant more servers, databases, hosting costs, ongoing maintenance, and rebuilding purchase flows and subscription screens. For Android, I didn't even have a server-side validation option — I just had to trust the billing library response client-side, with no way to detect refunds or verify anything independently.
So I decided to tackle it properly and built my own monetization system.
I figured others in the B4X community were probably hitting the same walls, so what started as a simple solution for my own apps turned into months of building both the B4X library and the backend infrastructure behind it — into a service any B4X developer can use.
Register your app, grab your API key, add the b4xlib, and you're ready to go in just a few lines of code:
That's it. Seriously.:
' Initialize with your App ID and API key from the dashboard
PurchaseManager.Initialize(Root, BILLING_KEY, APP_ID, API_KEY)
' Add your products
PurchaseManager.AddProduct("premium", "Premium", "Unlock all features")
' Show the purchase screen — that's it
Wait For (PurchaseManager.ShowInAppPurchase) Complete (Success As Boolean)Check status anytime — instant, from local cache:
Status & Validation:
If PurchaseManager.IsUnlocked Then ...
' Or trigger a live validation at any time
Wait For (PurchaseManager.ValidateNow) Complete (Success As Boolean)Key Features
• Built-in purchase and subscription screens (dark mode, theming, feature cards)
• Server-side validation — receipts verified directly with Apple and Google
• Zero secrets in your app — credentials stored securely server-side
• Smart caching — status checks are instant from local cache, background re-validation only when needed
• Restore purchases flow for both platforms
• Consumable product support
• Auto-generated privacy policy and terms of service (or supply your own URL/HTML)
• Subscription screens include Apple-required disclosures (auto-renewal terms, ToS/Privacy links) — App Store ready out of the box
• Non-purchasing users generate zero API calls
How It Works
1. Create an account at b4xpurchasemanager.com and register your app
2. Upload your store credentials (Apple Shared Secret / Google Play service account)
3. Grab your API key from the dashboard
4. Add the b4xlib to your project and initialize
5. The library handles everything — purchase UI, store interaction, receipt validation, caching, and status management
Your app talks to the BPM validation server over HTTPS. The server verifies receipts directly with Apple/Google and returns the result. No secrets in your app, no server to maintain.
Setup
1. Copy B4XPurchaseManager.b4xlib to your B4X Additional Libraries folder
2. iOS: Your provisioning profile must be based on an explicit App ID (e.g., com.yourcompany.yourapp) — wildcard profiles (com.*) will not compile
3. Android: Add the following to your manifest:
Android Manifest:
CreateResourceFromFile(Macro, GooglePlayBilling.GooglePlayBilling)Add your constants to Class_Globals:
Constants:
Private Const BILLING_KEY As String = "MIIBIjANBgkq..." ' Your Google Play license key (ignored on iOS)
Private Const APP_ID As String = "my-app" ' Your BPM dashboard app identifier
Private Const API_KEY As String = "bpm_your_key_here" ' Your BPM API keyIn-App Purchase Example (One-Time Unlock)
In-App Purchase:
Private PurchaseManager As B4XPurchaseManager
Private Sub B4XPage_Created (Root1 As B4XView)
Root = Root1
Root.LoadLayout("MainPage")
PurchaseManager.Initialize(Root, BILLING_KEY, APP_ID, API_KEY)
PurchaseManager.DisplayAppName = "My App"
PurchaseManager.AddFeature("🎨", "Premium Themes", "Access all premium themes")
PurchaseManager.AddFeature("🚀", "Advanced Features", "Unlock powerful tools")
PurchaseManager.AddProduct("premium_unlock", "Premium", "Unlock all features")
End Sub
Private Sub btnPurchase_Click
Wait For (PurchaseManager.ShowInAppPurchase) Complete (Success As Boolean)
If Success Then xui.MsgboxAsync("Purchase successful!", "Success")
End Sub
Private Sub btnRestore_Click
Wait For (PurchaseManager.RestorePurchases) Complete (Success As Boolean)
End Sub
Private Sub B4XPage_Appear
PurchaseManager.CheckStatus
If PurchaseManager.IsUnlocked Then
' Show premium features
End If
End Sub
Sub B4XPage_CloseRequest As ResumableSub
If PurchaseManager.IsActive Then
PurchaseManager.HidePurchaseScreen
Return False
End If
Return True
End SubSubscription Example (Monthly + Yearly)
Subscriptions:
Private PurchaseManager As B4XPurchaseManager
Private Sub B4XPage_Created (Root1 As B4XView)
Root = Root1
Root.LoadLayout("MainPage")
PurchaseManager.Initialize(Root, BILLING_KEY, APP_ID, API_KEY)
PurchaseManager.DisplayAppName = "My App"
PurchaseManager.AddFeature("⭐", "Premium Access", "Full access to all features")
PurchaseManager.AddFeature("🔄", "Cross-Platform", "Works on Android and iOS")
' Required for subscriptions
PurchaseManager.PolicyCompanyName = "Your Company"
PurchaseManager.PolicyEmailAddress = "support@yourcompany.com"
PurchaseManager.PolicyEffectiveDate = "January 1, 2025"
' BasePlanId must match Google Play Console (ignored on iOS)
PurchaseManager.AddSubscription("premium_monthly", "monthly-plan", _
"Monthly Premium", "Full access, billed monthly", "Monthly")
PurchaseManager.AddSubscription("premium_yearly", "yearly-plan", _
"Yearly Premium", "Full access, billed yearly — save 40%", "Yearly")
End Sub
Private Sub btnSubscribe_Click
Wait For (PurchaseManager.ShowSubscriptionPurchase) Complete (Success As Boolean)
If Success Then xui.MsgboxAsync("Subscription activated!", "Success")
End Sub
Private Sub btnRestore_Click
Wait For (PurchaseManager.RestoreSubscriptions) Complete (Success As Boolean)
End Sub
Private Sub B4XPage_Appear
PurchaseManager.CheckStatus
If PurchaseManager.IsSubscriptionActive Then
' Show premium features
End If
End Sub
Sub B4XPage_CloseRequest As ResumableSub
If PurchaseManager.IsActive Then
PurchaseManager.HidePurchaseScreen
Return False
End If
Return True
End SubAdditional Features
Direct Purchase (Custom UI), Theming, Consumables, Debug:
' ── Direct Purchase (use your own UI instead of built-in screens) ──
Wait For (PurchaseManager.PurchaseProduct("premium_unlock")) Complete (Success As Boolean)
Wait For (PurchaseManager.PurchaseSubscription("premium_monthly", "monthly-plan")) Complete (Success As Boolean)
' ── Theming ──
PurchaseManager.DarkMode = True
PurchaseManager.SetThemeColors(0xFF6366F1, 0xFF8B5CF6, 0xFFEC4899, 0xFFFFFFFF, 0xFFF5F5F7)
' ── Consumables ──
PurchaseManager.AddConsumableProduct("power_boost", "Power Boost", "Boost your power", 10)
If PurchaseManager.UseConsumables(1) Then Log("Consumed 1 item")
Dim count As Int = PurchaseManager.GetConsumableCount
' ── Debug & Testing ──
PurchaseManager.DebugValidation = True ' Faster cache intervals for development
Wait For (PurchaseManager.ResetPurchaseForTesting("premium_unlock")) Complete (Success As Boolean)
Wait For (PurchaseManager.ResetSubscriptionForTesting("premium_monthly")) Complete (Success As Boolean)
' ── Privacy Policy & Terms Export (debug only) ──
PurchaseManager.ExportPrivacyPolicyInapp ' Logs full HTML to IDE log
PurchaseManager.ExportPrivacyPolicySubscription
PurchaseManager.ExportTermsOfService
' Right-click HTML line in IDE log → Copy Line → paste into editor or LLM
' ── Custom Privacy Policy & Terms ──
PurchaseManager.CustomPrivacyPolicyInapp = "https://myapp.com/privacy.html" ' URL or HTML
PurchaseManager.CustomTermsOfService = "https://myapp.com/terms.html"Caching & Validation
The library uses smart caching so status checks are always instant. In-app purchases and subscriptions are cached independently — only the type whose cache has expired gets re-validated:
• New in-app purchases (first 14 days / refund window): re-validated every 24 hours
• Established in-app purchases (after 14 days): re-validated every 14 days (~2 credits/month)
• Active subscriptions: re-validated every 24 hours (~30 credits/month)
• Expired subscriptions: go dormant after 7-day grace period (zero cost)
• Refunded purchases: go dormant immediately (zero cost)
• Users who never purchased: zero API calls, zero credits consumed
CheckStatus reads from local cache instantly. Background validation only triggers when cache expires. Blended average: ~15 validations per paying user per month.
Pricing
1 credit = 1 validation. Free tier: 500 credits/month (no credit card required). Paid tiers start at $5/month.
You only pay for active paying users — non-purchasers, expired subs, and refunded users all cost zero.
Validation typically costs less than 1% of what your paying users generate in revenue.
METHODS REFERENCE:
| Method | Returns | Description |
|---|---|---|
| Initialize(Parent, BillingKey, AppId, ApiKey) | — | Initialize the library. Pass Root for Parent. Pass "" for BillingKey on iOS. AppId is your BPM dashboard app identifier. ApiKey is required (starts with "bpm_"). |
| IsInitialized | Boolean | True if Initialize has been called successfully |
| AddProduct(ProductId, Title, Description) | — | Add a non-consumable product |
| AddConsumableProduct(ProductId, Title, Description, Quantity) | — | Add a consumable product. Quantity defines how many consumables are automatically awarded per purchase. |
| ClearProducts | — | Remove all configured products |
| AddSubscription(ProductId, BasePlanId, Title, Description, Period) | — | Add a subscription |
| ClearSubscriptions | — | Remove all configured subscriptions |
| ShowInAppPurchase | Boolean | Show purchase screen. True = success |
| ShowSubscriptionPurchase | Boolean | Show subscription screen. True = success |
| PurchaseProduct(ProductId) | Boolean | Purchase directly without built-in screen |
| PurchaseSubscription(ProductId, BasePlanId) | Boolean | Subscribe directly without built-in screen |
| RestorePurchases | Boolean | Restore in-app purchases from store |
| RestoreSubscriptions | Boolean | Restore subscriptions from store |
| CheckStatus | — | Load cached status, trigger background validation if expired |
| ValidateNow | Boolean | Force immediate live validation (costs 1 credit per configured type) |
| IsUnlocked | Boolean | True if user owns a non-consumable product |
| IsSubscriptionActive | Boolean | True if user has valid subscription |
| GetActiveSubscriptionId | String | Active subscription product ID, or "" if none |
| GetSubscriptionExpiryDate | Long | Subscription expiry date in ticks, or 0 if not available |
| IsActive | Boolean | True if purchase/subscription screen is showing |
| ValidationInProgress | Boolean | True if live backend validation is currently running |
| HidePurchaseScreen | — | Close any active purchase/subscription screen |
| AddConsumables(Count) | — | Manually add consumables (for custom UI purchases, ad rewards, referral bonuses, etc.) |
| UseConsumables(Count) | Boolean | Deduct consumables. True if enough available |
| GetConsumableCount | Int | Current consumable count |
| SetConsumableCount(Count) | — | Set count directly (for server sync) |
| SetThemeColors(Primary, Secondary, Accent, Bg1, Bg2) | — | Set theme colors. Pass 0 for defaults |
| AddFeature(Emoji, Title, Description) | — | Add feature card to purchase screens |
| ClearFeatures | — | Remove all feature cards |
| ShowPrivacyPolicy | — | Show privacy policy overlay |
| ShowTermsOfService | — | Show terms of service overlay |
| ExportPrivacyPolicyInapp | Boolean | Export in-app privacy policy HTML to IDE log. Debug only. |
| ExportPrivacyPolicySubscription | Boolean | Export subscription privacy policy HTML to IDE log. Debug only. |
| ExportTermsOfService | Boolean | Export terms of service HTML to IDE log. Debug only. |
| ResetPurchaseForTesting(ProductId) | Boolean | Reset a purchase for re-testing. Android: consumes token. iOS: clears cache. |
| ResetSubscriptionForTesting(ProductId) | Boolean | Reset a subscription for re-testing. |
PROPERTIES REFERENCE:
| Property | Type | Description |
|---|---|---|
| DisplayAppName | String | App name on purchase screens (default: your app's name) |
| DisplayTagline | String | Tagline below app name (default: "Unlock the Full Experience") |
| DarkMode | Boolean | Dark theme (default: False) |
| PolicyCompanyName | String | Company name for legal templates |
| PolicyEmailAddress | String | Contact email for legal templates |
| PolicyEffectiveDate | String | Effective date for legal documents |
| CustomPrivacyPolicyInapp | String | Custom privacy policy — URL or HTML |
| CustomPrivacyPolicySubscription | String | Custom subscription privacy policy — URL or HTML |
| CustomTermsOfService | String | Custom terms — URL or HTML |
| DebugValidation | Boolean | Faster revalidation intervals for testing (default: False) |
| AdvancedDebugMode | Boolean | Logs exactly what the store returned when products don't show up — the IDs requested, what came back, and what didn't. (default: False) |
| AutoInappValidation | Boolean | By default, in-app purchases only re-validate for the first 21 days (covering the refund window). Turn on to keep auto-validating every 14 days indefinitely for extra coverage, or use ValidateNow when/if required. (default: False) |
Links
• Website & Docs: https://b4xpurchasemanager.com
• Dashboard: https://app.b4xpurchasemanager.com
Step-by-step guides for Android setup, iOS setup, Google Play service account, Apple Shared Secret, and more are available on the website — along with a detailed FAQ.
v1.01 Added auto-restore: automatically checks store for existing purchases on first launch (new device, reinstall, migration)
v1.02 Added AdvancedDebugMode: logs exactly what the store returned when products don't show up — the IDs requested, what came back, and what didn't.
Added AutoInappValidation: by default, in-app purchases only re-validate for the first 21 days (covering the refund window), then stop — you re-validate later via ValidateNow. Turn this on to keep auto-validating every 14 days indefinitely for extra coverage.
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