A swimlane diagram is a type of flowchart that organizes a process into lanes, one for each person, team, or system involved. Each step sits in the lane of whoever owns it, and arrows that cross lanes show handoffs. Named after the lanes in a pool, it's also called a cross-functional flowchart. Teams use it to make accountability and handoffs in a process explicit.

Start by listing the parties in your process and giving each one a lane. Lay out the steps in order, placing each in the lane of whoever's responsible. Add decision diamonds where the path branches, and draw connectors across lanes to show handoffs. Keep one action per step. You can build one in Whimsical's flowchart maker and adjust the lanes as the process changes.

A standard flowchart shows what happens next, sequencing steps without saying who does them. A swimlane diagram adds that missing layer: it places each step in the lane of the person, team, or system responsible, so handoffs between parties are explicit. Use a plain flowchart for a single-owner process; use a swimlane when several parties share the work.

Reach for a swimlane diagram when a process involves more than one person, team, or system and you need to show who does what. It shines for cross-functional work: onboarding, approvals, order fulfilment, support escalations, anywhere work passes between parties. If a process has a single owner and no handoffs, a plain flowchart is simpler and enough.

In BPMN, the business process notation standard, a pool represents a whole participant or organization, and lanes are the sub-divisions inside it, usually roles or departments. A single company process often sits in one pool with a lane per team. Across two organizations, you'd use two pools. Most everyday swimlane diagrams just use lanes.