Open Source Subscription Management
This category splits cleanly in two, and both halves are about losing track of recurring money. One side is for a person watching every subscription quietly drain a card and wanting the renewal dates, budgets, and reminders in one place. The other is billing infrastructure that charges customers on a recurring or usage-based meter, where the hard part is representing plans, proration, and metered usage as they change over time. The open source options here cover both ends without becoming yet another subscription: the personal trackers run on your own machine, and the billing engines let you own the pricing logic, invoicing, and payment records instead of renting them from a platform that takes a cut of every charge.
Lago
Open-source billing infrastructure for usage-based, subscription-based, and hybrid pricing models
Wallos
Self-hostable personal subscription tracker for recurring payments, budgets, and multi-currency expenses
Kill Bill
Open-source subscription billing and payments platform with real-time analytics and financial reports
Flexprice
Open-source billing infrastructure for usage-based, credit-based, and hybrid pricing
Open Collective
Online funding platform for open communities to raise money and share finances transparently
OpenMeter
Open-source metering and billing platform for usage-based AI, API, and DevTool monetization
SubTrackr
Self-hosted subscription tracker with spending analytics, reminders, and export options
UniBee
Open-source billing software for SaaS subscriptions, invoices, transactions, and recurring payments
Our picks
Best usage-based billing engine: Lago Lago is API-first billing infrastructure for usage-based, subscription, and hybrid pricing, exposing every feature through a REST API with Node, Python, Ruby, and Go SDKs. It is payment-agnostic across Stripe, Adyen, and GoCardless, and adds prepaid credits, coupons, dunning, and revenue analytics. Self-host with Docker Compose when you want metering and billing fully under your control.
Best for complex subscription catalogs: Kill Bill Kill Bill is a mature platform for subscription billing and payments that runs on your own infrastructure with no per-transaction or revenue-based fees. It covers multiple billing models, trials, usage metering, wallets, and prepaid credits, with native Stripe, Adyen, Braintree, and PayPal integrations and the Kaui back-office UI, multi-tenancy, and RBAC for larger operations.
Best for real-time usage metering: OpenMeter OpenMeter is a metering and billing engine aimed at AI, API, and DevTool monetization. It ingests CloudEvents and aggregates usage with SUM, COUNT, AVG, MIN, and MAX meters, then bills with tiered, graduated, and flat-fee pricing, quotas, and prepaid credits. Self-host with Docker Compose or Kubernetes when you need real-time usage limits and balances.
Best personal subscription tracker: Wallos Wallos is a self-hostable tracker for your own recurring payments, replacing spreadsheets with due dates, categories, and spending stats. It supports multi-currency tracking with live exchange rates, notifications by email, Telegram, Discord, and webhooks, and OIDC login. Install with Docker or on bare metal when you just want visibility into what you are paying for.
Personal tracker or billing engine - decide which problem you have
The first thing to settle is which half of this category you actually need, because a personal tracker and a billing engine share almost nothing under the hood. If you just want to see recurring charges before they hit your card, SubTrackr and Wallos give you dashboards, renewal calendars, multi-currency totals, and reminders, with nothing about customers or invoices to operate. If you charge other people, you need real billing infrastructure, and the evaluation gets much harder.
For a billing engine, judge the pricing model before the checkout page. The difficulty shows up when plans change after purchase - upgrades, trials, pauses, coupons, seat changes, and usage overages all need predictable proration and versioned pricing. Lago, Kill Bill, UniBee, Flexprice, and OpenMeter differ most in how they meter usage and rate it: OpenMeter and Flexprice are built around real-time usage events and credits, while Kill Bill and UniBee center on catalogs, plans, and invoicing. Match the engine to whether you sell flat recurring plans, metered usage, or a hybrid.
Whatever you pick, separate payment collection from subscription state and check the exit path early, because these records live for years. Most engines integrate a gateway like Stripe or PayPal rather than touching card data directly, so confirm how retries, dunning, and webhook failures are reconciled, and whether an account's entitlement can be read cleanly. Subscriptions, plan versions, invoices, payments, and gateway reference IDs should all export in a form another system can reconcile without guessing at your historical billing rules.
Related categories
Frequently asked questions
Do these tools process credit cards directly?+
Most do not, and that is deliberate. Billing engines like Lago, Kill Bill, and UniBee integrate a gateway - Stripe, PayPal, Adyen, GoCardless, Braintree - which keeps raw card data out of your servers and narrows your PCI scope. Lago is explicitly payment-agnostic and works with any gateway. Confirm how gateway tokens and reference IDs are stored, and whether a subscription can survive switching gateways later without rebuilding customer state.
Which of these handle usage-based or metered billing?+
Several are built for it. OpenMeter ingests CloudEvents and aggregates with SUM, COUNT, AVG, MIN, and MAX meters; Flexprice meters custom usage events with credits and top-ups; and Lago handles usage-based, subscription, and hybrid pricing from events. The details that matter are how usage is deduplicated, rated, and corrected, since duplicate events become overcharges. Check whether customers can see current usage before the invoice lands, to avoid surprise-bill support tickets.
What is the difference between the personal trackers and the billing tools here?+
They solve opposite problems. SubTrackr and Wallos are personal or household tools for tracking your own recurring costs, with dashboards, renewal reminders, and multi-currency totals - no customers, no invoices. UniBee, Lago, Kill Bill, Flexprice, and OpenMeter are revenue infrastructure that charges your customers and generates invoices. Do not evaluate one against the other; decide first whether you are watching spend or collecting it.
Will a billing engine replace my accounting software?+
Usually not. These tools track plans, renewals, invoices, credits, and payment status, but finance still needs revenue recognition, tax reporting, and bank reconciliation elsewhere. Kill Bill and UniBee include analytics and financial reports, yet the goal is a clean handoff: invoice exports, credit notes, payment references, and stable customer identifiers that your general ledger can reconcile without manual spreadsheet repair. Treat billing and accounting as connected, separate systems.
How much operational care does self-hosting a billing engine need?+
Treat it as core financial infrastructure, not a normal internal app. Missed renewals or duplicate invoices affect cash and customer trust, so you need reliable backups, monitoring, upgrade testing, and a rollback plan. Kill Bill and Lago are designed to run on your own infrastructure with no per-transaction fees, but that control is also responsibility. If your team lacks production operations experience, a managed or hybrid deployment is often safer at first.
Can I use these to accept community funding rather than run subscriptions?+
That is a narrower case. Open Collective is a funding platform for open, transparent communities to raise, manage, and disburse money publicly, rather than a billing engine you embed in a product. It runs as a hosted service with GraphQL and REST APIs and no documented self-hosting path. If your need is transparent community finances instead of customer billing, it targets a different problem than the metering engines here.
What happens if the billing project I depend on stalls?+
Because this is revenue infrastructure, plan the exit before you need it. Prefer engines with a conventional database, documented schema, and clear APIs - Kill Bill, Lago, and UniBee all expose their data - and keep written notes on your plan rules and billing cycles. If development slows you can usually keep operating for a while, but gateway API changes, tax updates, and security fixes tend to force a migration sooner than a normal app would.