Bowtie diagram
Map a hazard and top event to its threats and consequences, with the preventive and mitigative barriers on each line — the classic barrier-based bowtie risk picture. Pan, zoom and edit right on the canvas. Export SVG, PNG or PDF. Saved on your device.
Open Bowtie diagram →What is a bowtie diagram?
A free bowtie diagram maker that runs entirely in your browser. A bowtie is the classic barrier-based risk picture used in process safety and HSE: the hazard and its top event (the moment control is lost) sit at the knot in the centre, the threats that could cause the top event line up on the left with their preventive barriers, and the consequences that could follow line up on the right with their mitigative barriers. Escalation factors — the conditions that defeat or degrade a barrier — hang beneath their line in yellow, each with its own escalation-factor barriers. The diagram lays itself out automatically on an interactive canvas — drag to pan, scroll to zoom, jump to full screen, and edit everything in place: click any box for its menu (rename, add a barrier or escalation factor, set effectiveness, delete) and click again to rename inline. Rate each barrier good, fair or poor so weak lines of defence stand out, then export the diagram as an SVG vector or PNG image, a fully text-based PDF or Word barrier report (one numbered table per threat and consequence, descriptions included), or a JSON backup you can re-import later. Everything is saved on your device and works offline; nothing is uploaded.
How to use Bowtie diagram
- Define the hazard and top event — Name the hazard (the thing with potential to cause harm) and the top event — the moment control over it is lost, such as a loss of containment. You can also rename both directly on the canvas.
- Add the threats — Use the Threat button on the canvas (or the top event's menu) to add each credible cause that could release the top event, and name it in place.
- Add preventive barriers — Click the + on a threat's line to drop a barrier onto it, in the order the barriers would act. Reorder them any time from a barrier's menu.
- Add consequences and mitigative barriers — Do the same on the right-hand side: each outcome that could follow the top event, with the barriers that limit or stop the harm.
- Add escalation factors — Where a specific barrier can be defeated — a trip bypassed, a bund drain left open — click the small yellow + beneath that barrier (or use the barrier's menu) to attach an escalation factor to it, then add the escalation-factor barriers that keep the degradation under control.
- Rate, arrange and export — Rate each barrier good, fair or poor from its menu to colour its border, pan and zoom the canvas (Recenter refits the whole diagram, full screen gives it the entire display), then export from the Download menu — SVG/PNG of the diagram, a text-based PDF or Word barrier report, or JSON for backup.
Frequently asked questions
What goes in the top event?
The moment you lose control of the hazard — for example "loss of containment" — not the final harm. Fires, injuries and environmental damage belong on the right-hand side as consequences.
What is the difference between preventive and mitigative barriers?
Preventive barriers act before the top event to stop a threat releasing it; mitigative barriers act after the top event to limit how bad the consequences become.
Can I edit the diagram directly on the canvas?
Yes. Click any box to open its inline menu — rename, add a barrier, set effectiveness, reorder or delete — and click it again (or press Enter) to edit the text in place. Drag empty canvas to pan, scroll to zoom, and use the Recenter and full-screen controls.
What is an escalation factor?
A condition that defeats or degrades a specific barrier — for example a level trip bypassed for maintenance. It attaches to the barrier it degrades: all of a barrier's escalation factors share one connection that branches to each factor, and the threat line stretches so the chains always fit without crossing. You can collapse escalation factors globally from the toolbar or per barrier from the small toggle beneath it — hidden branches show a yellow count badge, and clicking it (or adding a new escalation factor) expands them again. Exports always include the full diagram.
Can I add descriptions?
Yes — every threat, consequence, barrier, escalation factor and EF barrier has a description field in the cards below the canvas, or via the Description button in its canvas menu. Descriptions stay off the diagram itself; a subtle corner mark shows which boxes carry one, and they appear in full in the PDF tables.
What export formats are available?
The diagram exports as an SVG vector or a high-resolution PNG. The PDF and Word exports are text-based barrier reports — one numbered table per threat and per consequence with IDs, effectiveness and descriptions — so the text stays selectable and editable. A JSON export backs up the whole bowtie, and Import JSON loads it back (or moves it between devices).
Tips
- Keep barriers to real, auditable controls — a valve, a trip, a bund, a tested procedure. Vague entries like "training" or "safety culture" are not barriers.
- Order the barriers on each line in the sequence they would act in time — the diagram draws them in list order, and each barrier's menu can move it earlier or later.
- Use the effectiveness colours during barrier reviews: the red and amber borders show where to focus improvement work.
- Use escalation factors sparingly — only for credible ways a barrier fails that you actively manage; each one should carry at least one escalation-factor barrier.