Image Height and Width Required

ID

html.height_width_required

Severity

low

Remediation Complexity

low

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

Html

Tags

reliability

Description

Flags an <img> element that does not declare both a width and a height attribute.

Rationale

When the intrinsic dimensions of an image are known up front, the browser can reserve the exact layout box before the image loads. Without them, content reflows once the image arrives, producing Cumulative Layout Shift that hurts perceived performance and the page’s Core Web Vitals.

<img src="a.png" alt="x">                         <!-- FLAW — no dimensions -->
<img src="a.png" alt="x" width="100">             <!-- FLAW — height missing -->

<img src="a.png" alt="x" width="100" height="50"> <!-- OK — both declared -->

Remediation

Add width and height attributes matching the image’s intrinsic aspect ratio. Use CSS (for example height: auto) if the rendered size must be responsive while still reserving space.

References