Block Formatting Context

Updated 05 Oct 2026

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What it is
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  a region participating in block layout with its own rules for interactiosn with floats and surrounding layout
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Creation
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  display: flow-root explicitly establishes one
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  other mechanisms, including certain overflow values, can establish one as a side effect
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Effects
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  can contain internal floats and prevent margins from collapsing acoss the context boundary
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  does not universally disable all margin collapsing inside the context
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Caution
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  a block formatting context is not automatically a containing block for absolutely positioned descendants
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  using overflwo solely to create one can introduce unwanted clipping or srollbars
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Reference
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  https://developer.mozilla.org/en-US/docs/Web/CSS/Guides/Display/Block_formatting_context
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