# Introduction

ProductLense joins your website analytics to your billing, then subtracts ad spend and processor fees, so you see profit per channel.

ProductLense is product analytics for founders who sell online. One script counts visitors without cookies, one billing connection brings in every charge and refund, and ProductLense joins the two at the moment each payment is written. The result is revenue, fees and profit for every channel that sent you a paying customer.

## What ProductLense answers

- Which channel brought the customers who pay, not just the visitors who click.
- How much each channel earned after processor fees and refunds.
- Whether a paid channel makes money once its ad spend is subtracted.
- How revenue from each channel holds up month after month.

## How the pieces fit

| Piece | What it does | Where to start |
|---|---|---|
| Tracking script | Counts pageviews, sessions and custom events, about 2.3 KB gzipped, no cookies | [Install the script tag](/docs/install/script-tag) |
| `identify` | Links a visitor to your own user id after signup or login | [Identify users](/docs/track/identify-users) |
| Billing connection | Reads customers, subscriptions, payments, refunds and fees from your provider | [Connect billing](/docs/revenue/connect-billing) |
| Ad spend | Spend per channel and campaign, entered by hand or as CSV | [Add ad spend](/docs/profit/ad-spend) |

A payment is attributed through a chain: payment, then customer, then your user id, then the visitor, then that visitor's first touch. Each link is described in [How payments are attributed](/docs/revenue/attribution).

## Where to go next

- New to ProductLense: follow the [Quickstart](/docs/get-started/quickstart). It takes about five minutes.
- Want the definitions first: read [How ProductLense counts](/docs/get-started/how-productlense-counts).
- Sending data from a server: see the [Events API](/docs/api/events) and the [Payments API](/docs/api/payments).
- Checking what is collected: see [What ProductLense collects](/docs/privacy/what-productlense-collects).