References

Beginner-friendly references for web development, with live, editable examples.

The HTML ondrag event

Event All modern browsers Updated
Quick answer

The HTML ondrag attribute runs JavaScript when a draggable element is being dragged. It is an inline handler for the drag event; in modern code prefer addEventListener('drag', …).

Overview

The ondrag event attribute runs JavaScript repeatedly while an element is dragged. In JavaScript the event itself is named drag — drop the on prefix when you call addEventListener.

It is part of the native HTML drag-and-drop API. The handler receives a DragEvent whose dataTransfer object carries the dragged data. One rule trips everyone up: you must call event.preventDefault() in the ondragover handler of a target, or it will not accept a drop.

You can wire this up with the inline ondrag HTML attribute, but the modern, recommended approach is element.addEventListener('drag', handler) in JavaScript. That keeps behavior out of your markup, lets you attach several handlers to the same event, and makes them easy to remove. The inline attribute is fine for quick demos.

Syntax

<element ondrag="handler()">…</element>

element.addEventListener('drag', handler);

Best practices

  • Prefer element.addEventListener('drag', handler) over the inline ondrag attribute — it separates behavior from markup and allows multiple handlers.
  • Call preventDefault() in ondragover so the element can act as a drop target.
  • Set and read the payload through event.dataTransfer.
  • Provide a keyboard-accessible alternative — native drag-and-drop is hard to use without a mouse.

Frequently asked questions

What is the ondrag event?
It runs JavaScript repeatedly while an element is dragged. In JavaScript the event is named drag.
Why is my drop not working?
You must call event.preventDefault() in the ondragover handler, otherwise the element rejects the drop.
How do I pass data between dragged and dropped elements?
Use event.dataTransfer.setData() when the drag starts and getData() when it drops.
Should I use the ondrag attribute or addEventListener?
Prefer addEventListener('drag', …) in JavaScript. The inline ondrag attribute works but mixes behavior into the markup and allows only one handler per element.
ondblclick ondragend