What's the Difference Between `offsetWidth`, `clientWidth`, and `scrollWidth` (and Their Height Counterparts)?

Understanding offsetWidth, clientWidth, scrollWidth, and Their Height Counterparts

Despite numerous inquiries on StackOverflow and confusing or inaccurate information online, understanding the intricacies of offsetWidth, clientWidth, scrollWidth, and their height counterparts remains a challenge.

Definitions and Visual Aids:

• offsetWidth, offsetHeight: Represent the width and height of the element's visual box, including borders. Can be calculated by summing width/height, paddings, and borders (for elements with display: block).
• clientWidth, clientHeight: Indicate the visible portion of the content within the element, excluding borders and scrollbars, but including padding. Cannot be directly derived from CSS and varies based on the system's scrollbar size.
• scrollWidth, scrollHeight: Indicate the total size of the element's content, including hidden portions outside the scroll area. Also dependent on content and cannot be calculated directly from CSS.

[Visual of CSS2 Box Model with labeled dimensions]

Calculating Scroll Bar Width:

Since offsetWidth includes scrollbar width, we can calculate it using the formula:

scrollbarWidth = offsetWidth - clientWidth - getComputedStyle().borderLeftWidth - getComputedStyle().borderRightWidth

However, this method may yield rounding errors due to the integer nature of offsetWidth and clientWidth, which may not reflect actual fractional dimensions at zoom levels other than 1.

Additional Considerations:

Note that the following formula:

scrollbarWidth = getComputedStyle().width + getComputedStyle().paddingLeft + getComputedStyle().paddingRight - clientWidth

does not provide reliable results in Chrome, as Chrome subtracts scrollbar width from the reported width. Additionally, Chrome renders paddingBottom to the bottom of the scroll content, unlike other browsers.

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