--- title: heading‍offset is Not the Document Outline Algorithm description: The `headingoffset` HTML attribute, recently announced for Firefox behind a flag, is being mistakenly celebrated as a revival of the long-dead Document Outline... canonical: https://daily.dev/posts/heading-offset-is-not-the-document-outline-algorithm-ixqmdwm36 twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: heading‍offset is Not the Document Outline Algorithm | daily.dev og:description: The `headingoffset` HTML attribute, recently announced for Firefox behind a flag, is being mistakenly celebrated as a revival of the long-dead Document Outline... og:url: https://daily.dev/posts/heading-offset-is-not-the-document-outline-algorithm-ixqmdwm36 og:image: https://api.daily.dev/og/posts/ixQmdWm36.png og:image:alt: heading‍offset is Not the Document Outline Algorithm og:image:width: 1200 og:image:height: 630 og:locale: en --- [Adrian Roselli](https://daily.dev/sources/adrianroselli) [Read post](https://api.daily.dev/r/ixQmdWm36) # [heading‍offset is Not the Document Outline Algorithm](https://api.daily.dev/r/ixQmdWm36 "Go to post") The \`headingoffset\` HTML attribute, recently announced for Firefox behind a flag, is being mistakenly celebrated as a revival of the long-dead Document Outline Algorithm. It is not. \`headingoffset\` lets authors manually offset heading levels for descendants of a given node — useful for content reuse — but it still requires intentional author decisions. The browser gains no new understanding of content structure. Key constraints: values must be non-negative integers between 0 and 8, values over 8 max at level 9, and \`headingreset\` can override it. Authors should not use it until browser support is confirmed, and should not expect it to automatically resolve heading level problems in imported or user-generated content, as doing so risks WCAG violations. [#html](/tags/html "Check all #html posts")[#accessibility](/tags/accessibility "Check all #accessibility posts") Jun 11•4m read time•From [adrianroselli.com](https://api.daily.dev/r/ixQmdWm36 "adrianroselli.com") [](https://api.daily.dev/r/ixQmdWm36 "Go to post") Table of contents [Background # anchor](https://api.daily.dev/r/ixQmdWm36?a=Background "Background # anchor")[headingoffset # anchor](https://api.daily.dev/r/ixQmdWm36?a=headingoffset "headingoffset # anchor")[Recap # anchor](https://api.daily.dev/r/ixQmdWm36?a=Recap "Recap # anchor")[Related # anchor](https://api.daily.dev/r/ixQmdWm36?a=Related "Related # anchor")[Tags](https://api.daily.dev/r/ixQmdWm36 "Tags")[Other Posts](https://api.daily.dev/r/ixQmdWm36 "Other Posts")[No comments? Be the first!](https://api.daily.dev/r/ixQmdWm36 "No comments? Be the first!") 86.3K Impressions40 Upvotes1 Repost Comment Bookmark Copy Share your thoughtsPost [](https://daily.dev/sources/adrianroselli) [Adrian Roselli](https://daily.dev/sources/adrianroselli "https://daily.dev/sources/adrianroselli") Adrian Roselli is a web developer, accessibility advocate, and expert in web standards. Readers can ... Read more 37 Followers • 203 Upvotes #### Would you recommend this post? 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