Skip to content
Learn Measure Blog Case studies About
On this page
  • How the Lighthouse font size audit fails
  • How to fix illegible fonts
  • How to fix a missing viewport config
  • Resources

Document doesn't use legible font sizes

May 2, 2019 — Updated Aug 20, 2019
Appears in: SEO audits
On this page
  • How the Lighthouse font size audit fails
  • How to fix illegible fonts
  • How to fix a missing viewport config
  • Resources

Many search engines rank pages based on how mobile-friendly they are. Font sizes smaller than 12 px are often difficult to read on mobile devices and may require users to zoom in to display text at a comfortable reading size.

How the Lighthouse font size audit fails #

Lighthouse flags pages with font sizes that are too small to read easily on mobile:

Lighthouse audit showing page has illegible font sizes

Lighthouse flags pages on which 60% or more of the text has a font size smaller than 12 px. When a page fails the audit, Lighthouse lists the results in a table with four columns:

SourceThe source location of the CSS ruleset that is causing the illegible text.
SelectorThe selector of the ruleset.
% of Page TextThe percentage of text on the page that is affected by the ruleset.
Font SizeThe computed size of the text.
Each SEO audit is weighted equally in the Lighthouse SEO Score, except for the manual Structured data is valid audit. Learn more in the Lighthouse Scoring Guide.

How to fix illegible fonts #

Check font sizes in your CSS. Aim to have a font size of at least 12 px on at least 60% of the text on your page.

How to fix a missing viewport config #

If Lighthouse reports Text is illegible because of a missing viewport config, add a <meta name="viewport" content="width=device-width, initial-scale=1"> tag to the <head> of your document.

See the Does not have a <meta name="viewport"> tag with width or initial-scale post for more information.

Resources #

Source code for Document does not use legible font sizes audit

Last updated: Aug 20, 2019 — Improve article
Return to all articles
Share
subscribe

Contribute

  • File a bug
  • View source

Related content

  • developer.chrome.com
  • Chrome updates
  • Web Fundamentals
  • Case studies
  • Podcasts
  • Shows

Connect

  • Twitter
  • YouTube
  • Google Developers
  • Chrome
  • Firebase
  • Google Cloud Platform
  • All products
  • Terms & Privacy
  • Community Guidelines

Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 4.0 License, and code samples are licensed under the Apache 2.0 License. For details, see the Google Developers Site Policies.