Kilotest: Diagnoses of sizes attribute invalid violation by HTML element 578 on Mozilla Foundation page

Basics

About the page

• URL: https://www.mozilla.org/en-US/
• Tested 32 days ago on 2026-09-08 at 04:02 by job 260908T0359-xmh
• Summary of results:
  • Rule engines:
    • Called: 12
    • Were able to test: 12
    • Reported any rule violations: 11
  • Violations: 753
  • Violators: 192
  • Issues: 47
• Download the full technical report (JSON)

About the issue

• Why it matters: Item behaves improperly
• Priority: highest
• Related WCAG standard: 1.3.1
• Reported by 1 rule engine (Html Checker API)
• Violations: 1
• Violators: 1

About the violator

• Tag name: IMG
• Text: [not applicable]
• Start tag: <img alt="Choose Your Future" class="" height="515" sizes="1376px" src="https://www.mozilla.org/media/cms/images/showcase-som-2025.width-1376.png" width="1376">
• XPath: /html/body/div[2]/main[1]/div[6]/div[1]/div[1]/div[1]/figure[1]/img[1]
• Bounding box: x = 272, y = 5402, width = 1376, height = 515
• Reported by Html Checker API

Diagnoses

Here is how rule engines diagnose the sizes attribute invalid issue for HTML element 578 of the Mozilla Foundation page.

1. The sizes attribute must only be specified if the srcset attribute is also specified.

   Rule engine: Html Checker API (World Wide Web Consortium)