Sideways scrolling on mobile: Crawl Audit check 103

Short answer: people scroll down, not sideways. When something on the page is wider than the screen, the whole page wobbles side to side and content gets cut off. Check 103 warns when it finds signs of content wider than a phone.

What Crawl Audit checks

• Warning: the HTML contains a fixed width of 1,000 pixels or more, such as width: 1200px.
• Pass: no such width in the markup.
• Crawl Audit was first built to read a PageSpeed audit called "content-width", which was removed in Lighthouse 12 in 2024. Since 6 October 2026 it reads the markup only. It can't see widths set in separate stylesheets, so test on a real phone too.

What the sources say

• WCAG 1.4.10 Reflow (level AA): content must work "without requiring scrolling in two dimensions" at "a width equivalent to 320 CSS pixels". That's the same as a 1,280 pixel window zoomed to 400%.
• web.dev: "users are used to scrolling websites vertically but not horizontally. Forcing the user to scroll horizontally or to zoom out to see the whole page causes a poor user experience."

Common causes

• Images, videos or embeds with a fixed width. web.dev: "an image displayed wider than the viewport can cause horizontal scrolling."
• Tables with many columns.
• Long unbroken text such as URLs or codes.
• Containers set in pixels rather than percentages.

How to fix it

img, video, iframe { max-width: 100%; height: auto; }
.table-wrap { overflow-x: auto; }
p { overflow-wrap: anywhere; }

Wrapping a wide table in its own scrolling box keeps the sideways scroll to the table, not the page. Then check at 320 pixels wide in your browser's device mode.

Sources

• W3C, Understanding 1.4.10 Reflow, checked 6 October 2026.
• web.dev, Responsive web design basics; Lighthouse, changelog (12.0.0).