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HTML 

              
                <header>
	<h1>Troubleshooting a CSS Grid child element with <code>position: sticky</code></h1>
	<p>By <a href="https://mrwweb.com">Mark Root-Wiley</a>, September 24, 2021</p>
</header>
<main>
	<p class="note"><em>This post has a responsive layout. It's best read at a browser width of at least <code>48em</code> / <code>768px</code>.</em></p>
	<p>This is techncially a post about using CSS sticky positioning on grid children. This is actually just a story of an average day banging my head against the keyboard until I learned to see a problem in a different way, solve it with one line of CSS, and live happily every after&hellip; until at least tomorrow when I run into some new problem.</p>
	<p>It all started when I had a cool idea for my new resume (coming soon!) that involved a sticky sidebar with a list of my skills and some fun 🪄highlighty magic🪄 as you scrolled down the page.</p>
	<p>I was pretty familiar with the <a href="https://css-tricks.com/more-like-position-tricky/">many gotchas of <code>position: sticky</code></a>, and so I thought, "Hey, I've totally got a handle on all this fancy CSS stuff. Modern CSS makes layouts quick and easy!"</p>
	<p>The layout I wanted was basically the same as this demo: multiple elements, directly in the body, laid out with CSS Grid. Here, I'll save you from opening your dev tools:</p>
	<pre><code>&lt;body>
	&lt;header>&lt;/header>
	&lt;main>Left column&lt;/main>
	&lt;aside>Sticky Right Column&lt;/aside>
&lt;/body></code></pre>
	<p>The <code>body</code> uses <code>display: grid</code> to make a simple <code>2fr</code>/<code>1fr</code> sidebar layout and the <code>aside</code> has <code>position: sticky</code> and <code>top: 2em</code>.</p>
	<blockquote>
		<p>I'll be done in no time. Doo do doo do doo.</p>
		<p><em>[Writes two CSS rules]</em></p>
		<cite>Me, Being Predictably Naive</cite>
	</blockquote>
	<p>Half an hour later, I hadn't written any more code and was questioning everything. The only thing the sidebar was sticking to was the top of the page.</p>
	<p>I re-re-re-reviewed all the <a href="https://css-tricks.com/dealing-with-overflow-and-position-sticky/">things about sticky and overflow</a> and learned to think about <a href="https://elad.medium.com/css-position-sticky-how-it-really-works-54cd01dc2d46">sticky containers</a>. I read a lot about sticky positioning not working, but everything I read still didn't seem apply to my situation.</p>
	<p>In fact, it's the situation you find yourself in at this very moment. 🤨 Right now. On your screen. There is a sidebar that has had <code>position: sticky;</code> this whole time! 😱</p>
	<h2>See? I told you it didn't work!</h2>
	<p>Really. Keep scrolling. I'll wait&hellip;</p>
	<br><br><br><br><br><br><br>
	<p>The sidebar definitely isn't sticking, is it?</p>
	<p>At this point, I was really convinced that it <em>should</em> be working, but it wasn't. I was losing hope. This was probably some super technical edge-case-y thing that I just couldn't wrap my head around. Maybe I wasn't really a good front-end developer after all. <em>Good thing I'm editing my resume, so I can just remove "CSS" from the list of skills in the sidebar. It's for the best that it won't stick so my skills will just scroll out of view.</em> 😭</p>
	<p>But then! What's that? 😲 I noticed that for some odd reason, the sidebar stuck just a little bit. I can't even replicate that now, so I really don't know what I was seeing. (There's always more to learn!) What's important is that I kept searching. Almost immediately, I found a StackOverflow post&hellip; with no answers. I don't even think I had the same problem as the person who posted.</p>
	<p>One would not think this was the ⚡AHA! moment⚡, and yet:</p>
	<ol>
		<li>the post mentioned heights&hellip;</li>
		<li>which made me think about grid&hellip;</li>
		<li>which suddenly gave me the answer!</li>
	</ol>
	<p>Have you figured it out yet? Let me give you a hint:</p>
	<div class="toggle-wrapper">
		<input type="checkbox" id="outline"><label for="outline">Outline the Sidebar!</label>
	</div>
	<h2>The Solution</h2>
	<p>Ok, fine. I'll break it down for you.
	<p>Now that you've outlined the <code>aside</code> element, you can see that it's the same height as the <code>main</code> element containing all this ranty text!</p>
	<p>That's the "problem". Because as far as the browser is concerned, we <em>can</em> see the sidebar, it's just empty once you're this far down the page. Since it's always visible and within the viewport, the sticky part of <code>position: sticky</code> never kicks in.</p>
	<p>Why is this happening? The height of the <code>aside</code> is the expected behavior of a grid child element. With CSS grid layout, the default value for <code>align-items</code> is <code>stretch</code> (unless the element has an intrinsic size).</p>
	<p>So the solution is a single line of code. The sidebar needs <code>align-self: start</code>, so that its height doesn't stretch to match its parent's height and is only as tall as its content.</p>
	<p>Ready to fix it now? Go ahead, I'll let you do the honors 🏆:</p>
	<div class="toggle-wrapper">
		<input type="checkbox" id="fix"><label for="fix">Let there be stick!</label>
	</div>
	<p>It probably took me a good hour to go from 2 lines of broken CSS to 3 lines of working CSS, but now it works and it feels so good! And more importantly, I proved to myself that I really can do this whole website code-y thing after all. I'm sure you can too. Just keep working at it.</p>
</main>
<aside id="aside" aria-live="polite" aria-atomic="true" aria-relevant="text">
	<p>Don't mind me, I'm just a boring, normal, sidebar.</p>
	<p>🎉 You fixed it!<br>⭐ Gold star for you!</p>		
</aside>
!

CSS 

              
                /*
 * The Layout on medium-size screens and up
 */
@media (min-width: 48em) {
	body {
		display: grid;
		grid-template-columns: 2fr 1fr;
		grid-gap: 2em 5vw;
	}
	
	header {
		grid-column: 1 / -1;
	}

	aside {
		position: sticky;
		top: 2em;
	}
}

/*
 * Just making things prettier to look at below this
 */
* {
	margin: 0;
	box-sizing: border-box;
}

:focus {
	outline: 2px dotted Teal;
}
:focus:not(:focus-within) {
	outline: 0;
}

body {
	width: 90%;
	max-width: 100ch;
	margin: 5em auto;
	line-height: 1.5;
	font-size: 1.125rem;
	font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", "Ubuntu", "Roboto", "Noto Sans", "Droid Sans", sans-serif;
}

main, aside {
	margin-top: 2em;
}
@media (min-width: 48em) {
	main, aside {
		margin-top: 0;
	}
}

main * + * {
	margin-top: 1.5em;
}

header p {
	text-align: right;
	font-size: .875rem;
	color: DarkSlateGray;
}

header a {
	color: inherit;
}

a {
	color: Teal;
}
a:hover {
	text-decoration: none;
}

li {
	margin-top: .25em;
}

blockquote {
	padding-left: 1em;
	border-left: .25rem solid Teal;
}

cite {
	display: block;
	text-align: right;
	font-size: .875rem;
}
cite::before {
	content: '— '
}

main pre,
main code {
	background-color: PapayaWhip;
	padding: 0 .25em;
	border-radius: .1875rem;
	font-size: .9375rem;
	font-family: ui-monospace, "Cascadia Mono", "Segoe UI Mono", "Ubuntu Mono", "Roboto Mono", Menlo, Monaco, Consolas, monospace;
}

.toggle-wrapper {
	display: flex;
	justify-content: center;
	align-items: center;
	padding: 1em;
	border: .125rem solid Teal;
	font-size: 1.5rem;
}

input {
	accent-color: Teal;
	width: 1.5rem;
	height: 1.5rem;
}

label {
	margin: 0 0 0 .5em;
	cursor: pointer;
}

.note {
	background: WhiteSmoke;
	padding: 1em;
}

.outline {
	outline: 2px dashed Teal;
}

aside p:last-child {
	display: none;
}
.fix p:first-child {
	display: none;
}
.fix p:last-child {
	display: block;
}







/*
 * ⚠ SPOILER ALERT ⚠ Fix below.
 */














.fix {
	align-self: start;
}
!

JS 

              
                "use strict"

const toggleBodyClass = (e) => {
	const checkbox = e.currentTarget;
	document.getElementById('aside').classList.toggle(checkbox.id);
}

const checkboxes = document.querySelectorAll('input[type="checkbox"]');
console.log(checkboxes);
checkboxes.forEach( (cb) =>{ cb.addEventListener( 'click', toggleBodyClass ) });
!
999px

Console