> This page is for Unified. > For clean Markdown of any page, append .md to the page URL. > For a complete documentation index, see https://docs.merge.dev/llms.txt. > For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs.merge.dev/_mcp/server. # How Merge works > Core concepts — Merge Link, Linked Accounts, account tokens, the Unified API, and Common Models. Read this first. Your end user signs into their HR, accounting, or CRM system through a Merge-hosted UI called **Merge Link**. That produces a **Linked Account** and an account token you store in your database. You then call Merge's **Unified API**, which returns **Common Model** objects — a normalized shape that looks the same whether the data came from BambooHR, Workday, or Gusto. Below, each concept gets a definition and a concrete example, followed by a diagram of the token exchange that every Merge integration starts with. ### Merge Link A drop-in UI component that guides your end user through connecting to a third-party platform. You embed it in your frontend; your user picks an integration, signs in, and authorizes access. Merge handles the OAuth and credential exchange. ### Linked Account A connection between your app and a third-party platform, created when your end user completes Merge Link. Each Linked Account has an `account_token` you include in API requests to access that user's data. ### Unified API One API that lets you sync data from multiple third-party platforms. When you call `GET /hris/v1/employees`, Merge returns normalized employee records regardless of which HR platform your end user connected. ### Common Model A standardized data model that works the same across every provider in a category. For example, the `Employee` Common Model normalizes `first_name`, `last_name`, `work_email`, and `employments` across BambooHR, Workday, ADP, and 50+ other HRIS platforms. ### Dashboard The web application at [https://app.merge.dev](https://app.merge.dev) where you manage API keys, view Linked Accounts, monitor syncs, and configure integrations. During development, you can create test Linked Accounts directly in the Dashboard. --- ### Merge Link A drop-in UI component that guides your end user through connecting to a third-party platform. You embed it in your frontend; your user picks an integration, signs in, and authorizes access. Merge handles the OAuth and credential exchange. --- ### Linked Account A connection between your app and a third-party platform, created when your end user completes Merge Link. Each Linked Account has an `account_token` you include in API requests to access that user's data. --- ### Unified API One API that lets you sync data from multiple third-party platforms. When you call `GET /hris/v1/employees`, Merge returns normalized employee records regardless of which HR platform your end user connected. --- ### Common Model A standardized data model that works the same across every provider in a category. For example, the `Employee` Common Model normalizes `first_name`, `last_name`, `work_email`, and `employments` across BambooHR, Workday, ADP, and 50+ other HRIS platforms. --- ### Dashboard The web application at [app.merge.dev](https://app.merge.dev) where you manage API keys, view Linked Accounts, monitor syncs, and configure integrations. During development, you can create test Linked Accounts directly in the Dashboard. --- ## The token exchange Every production Merge integration follows the same four-step token exchange: 1. **Your backend** calls Merge to create a short-lived `link_token`. 2. **Your frontend** opens Merge Link with that `link_token`. Your end user picks an integration and signs in. 3. **Merge Link** returns a `public_token` to your frontend on success. 4. **Your backend** exchanges the `public_token` for a permanent `account_token` and stores it in your database. From that point on, every API request you make includes the `account_token` in the `X-Account-Token` header to identify which end user's data you are accessing. --- ## Where data lives Merge connects to your end users' third-party platforms, syncs data on a recurring schedule, and normalizes it into Common Models. You pull that data via the Unified API. Merge is the intermediary — your app never talks directly to the third party after the initial Merge Link authorization. For real-time updates, Merge can also send webhooks to your app when a sync completes or data changes. --- Next: Make your first API call Already familiar with the basics? Skip to [Merge Link](/merge-unified/merge-link) or the [Architecture reference](/merge-unified/architecture-reference).