Polar is a developer-first, open-source billing and monetization platform designed to help AI companies and software teams turn product usage into revenue. It provides a complete billing infrastructure that supports subscriptions, one-time payments, and especially usage-based pricing driven by real-time events.

At its core, Polar is built around event ingestion. Applications send usage events (such as API calls, token consumption, or feature usage), which are then aggregated into meters. These meters define how usage is measured and directly power billing calculations, enabling accurate, real-time charging based on actual product consumption.

The platform combines multiple layers of commerce infrastructure into one system: checkout flows, customer management, invoicing, metering, and global payments. It also acts as a merchant of record, handling tax compliance, VAT, GST, and international regulatory complexity so developers do not need to manage it themselves.

Polar is especially focused on modern AI and SaaS products, where pricing is often usage-based rather than flat subscription models. It enables developers to define pricing per unit (such as per token, per request, or per compute unit), and automatically converts those events into invoices and revenue streams.

The platform is API-first and integrates directly into codebases using SDKs, webhooks, and framework adapters. Developers can create products, define meters, ingest events, and generate checkout flows with minimal setup. It also includes customer portals, analytics, and entitlement systems for delivering access after purchase.

Polar is positioned as a full monetization stack rather than just a payment processor, combining billing logic, analytics, and commerce infrastructure into a single developer-focused system.

Key features include:

• Event-based usage billing (tokens, API calls, compute, etc.)
• Subscriptions, one-time payments, and hybrid pricing models
• Merchant of record handling (tax, VAT, GST, compliance)
• Checkout flows (hosted and embedded)
• Metering system for aggregating usage into billable units
• Customer management, invoices, and entitlements
• API-first design with SDKs and webhooks
• Built specifically for AI and modern SaaS monetization

Common use cases include:

• Monetizing AI APIs
• Charging per token or usage unit
• Running SaaS subscriptions
• Building developer tools with pay-per-use pricing
• Handling global payments without tax complexity
• Launching usage-based pricing models for modern software products

Polar is developed by Polar Software, Inc. and is part of the new generation of “usage-native” billing infrastructure tools focused on AI-first businesses and developer monetization.