The hardest part of building Lift wasn't the extraction. It was making the extracted code work outside the page it came from. And honestly, this problem nearly broke me.
When you pick an element on a website, its appearance is determined by dozens of CSS rules cascading from different stylesheets, media queries, CSS variables, inherited properties, and sometimes even JavaScript-driven styles. Rip the element out of that context and it looks nothing like what you selected. It's deflating to click "extract" and get something that doesn't even remotely resemble what you were looking at.
This is the core technical challenge of Lift, and it's the problem we've spent the most engineering time on. Every approach involves tradeoffs between output fidelity, code readability, and file size. Here's how we've navigated those tradeoffs.
Why Brute-Force CSS Extraction Fails
Our first approach was brute-force: compute every style on the element and inline it. This works, technically, but the output is a nightmare to read. A simple button might end up with 200+ inline style declarations, most of which are browser defaults that don't actually do anything visible.
Beyond readability, brute-force inlining creates maintenance nightmares. Every style is hardcoded, so changing a color or font size means hunting through hundreds of declarations. It also strips away the semantic meaning of the original CSS. You lose the information about which styles were intentional design choices and which were inherited defaults. That context matters enormously when you're trying to customize the code.
I saw this firsthand the first time I tried extracting a button from a popular marketing site. The brute-force output was over 4KB of CSS for a single button. Most of it was browser defaults and inherited properties that had zero visual effect. The same button, styled with only the declarations that actually mattered, needed maybe a dozen lines. The brute-force version was nearly impossible to read, let alone modify. I remember staring at it and thinking, "No one would ever want to use this."
Clean CSS Extraction With Style Diffing
What we do now is more surgical. Lift walks the DOM from your selected element down through all its children. For each node, we diff the computed styles against the browser defaults for that element type. Only the styles that actually differ (the ones that make this element look the way it does) get included.
This sounds straightforward, but browser defaults are surprisingly inconsistent. A <button> has different default styles than a <div>, and those defaults vary slightly across browsers. We maintain a normalized default style map for every HTML element type, updated with each major browser release, so our diffs are accurate regardless of which browser the user is running.
The diffing process also accounts for inheritance. If a parent element sets color: white and a child inherits it, we don't redundantly declare the color on the child. We trace the inheritance chain and include the declaration only where it originates. The result is clean, minimal CSS that produces the same visual output. When I first got this working correctly, it felt like a genuine breakthrough.
Resolving CSS Variables and Custom Property Chains
CSS variables add another layer of complexity. If an element uses var(--brand-color), we need to find where that variable is defined and include it in the extraction. We trace variable references up through the DOM to find the nearest definition, then include those declarations in a scoped :root block.
This gets tricky with variable chains. A variable might reference another variable, which references a third. Some design systems use dozens of intermediate tokens: --color-primary references --brand-500 which references --palette-green-500. Lift resolves the full chain and includes every link, preserving the ability to override at any level.
Keyframe animations and font-face declarations get the same treatment. If the extracted element uses them, they're included. If not, they're left out. The goal is the minimum viable stylesheet: everything the element needs to render correctly, and nothing it doesn't.
Extracting Responsive Styles and Media Queries
Responsive design adds yet another dimension. An element might look completely different at mobile versus desktop widths, with media queries changing layout, font sizes, spacing, and visibility. Lift captures all applicable media queries for the extracted element and includes them in the output.
We considered only extracting styles for the current viewport width, but that would mean your extracted component would break the moment someone resized their browser. Nobody wants that. Instead, we scan all loaded stylesheets for rules that match the extracted element at any breakpoint and include the full responsive behavior.
Preventing CSS Conflicts With Scope Isolation
Even with minimal CSS, pasting extracted styles into an existing project can cause conflicts. A class name like .container or .title is almost guaranteed to collide with existing styles. Lift addresses this by scoping all extracted CSS under a unique data attribute, so the styles only apply to the extracted element.
The scoped output uses a pattern like [data-lift-abc123] .original-class, which is specific enough to avoid conflicts without requiring you to rename anything. If you want to integrate the styles more permanently, the class names are all preserved in their original form. You just remove the scoping prefix and manage specificity yourself.
Known Limitations and What We're Improving
This approach isn't perfect. Styles that depend on parent layout, like flex children or grid items, can behave differently when extracted because their parent context changes. A flex child that was stretch-aligned in a column layout might collapse to its intrinsic size when placed in a different container.
Pseudo-elements like ::before and ::after are included, but pseudo-classes like :hover and :focus are trickier. We can capture the rules that would apply in those states, but we can't always determine if the original site uses JavaScript to toggle classes for hover effects instead of pure CSS. In those cases, the extracted hover state might be incomplete.
We're working on better heuristics for detecting and preserving layout context, including automatically wrapping extracted elements in a minimal parent container that replicates the original layout behavior. We're also improving our handling of container queries, which are becoming more common as browser support improves. It's a genuinely hard problem, but we're making real progress every week, and that keeps us motivated.