Stop Using Masonry Libraries (How the New CSS Grid Masonry Spec Finally Solved the Layout Performance Bottleneck)

How many times have you reached for a heavy JavaScript library just because you wanted a grid layout that didn't look like a boring 2012 Bootstrap template?

We’ve all been there. You want that "Pinterest look"—the staggered, uneven columns where items tuck neatly into the gaps left by the ones above them. But historically, CSS has been remarkably stubborn about this. You either used column-count (which breaks the reading order by flowing top-to-bottom instead of left-to-right) or you pulled in a 20KB library that calculates absolute positions on every window resize.

It's a performance nightmare. Every time a user resizes their browser, the JavaScript engine has to recalculate the bounding boxes of every single element and move them manually. It’s janky, it’s heavy, and frankly, it feels like we’re hacking the browser rather than working with it.

But the wait is almost over. The CSS Grid Level 3 spec is bringing native masonry support to the browser, and it’s a game changer for layout performance.

Why JavaScript Masonry is a Performance Sinkhole

Before we look at the new hotness, let’s talk about why the current way sucks. When you use something like Masonry.js or Isotope, you're essentially telling the browser to ignore its own layout engine.

1. Layout Thrashing: The script reads the height of an element, calculates a new position, and writes it back to the DOM. This causes a "reflow." Doing this for 50 items in a grid? Your CPU fans are going to start spinning.
2. The "Jump": You've seen it—the page loads, the items stack vertically for a split second, and then *snap*, the JavaScript kicks in and moves everything. It’s a jarring user experience.
3. Dependency Bloat: You’re adding extra kilobytes to your bundle for a layout that should, in an ideal world, be handled by five lines of CSS.

The New Way: grid-template-rows: masonry

The new specification is brilliantly simple. Instead of reinventing the wheel, it hooks directly into the existing CSS Grid module.

Here is how you define a masonry layout now:

.container {
  display: grid;
  gap: 1rem;
  /* Define your columns like normal */
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  
  /* This is the magic line */
  grid-template-rows: masonry;
}

That’s it. By setting grid-template-rows to masonry, you’re telling the browser: "Hey, don't worry about keeping the rows aligned. Just find the shortest column and stick the next item there."

Let’s look at a practical example

Imagine a gallery where images have different aspect ratios. Usually, this would leave massive white gaps in a standard grid.

<div class="masonry-grid">
  <div class="card short">1</div>
  <div class="card tall">2</div>
  <div class="card medium">3</div>
  <div class="card tall">4</div>
  <div class="card short">5</div>
</div>

.masonry-grid {
  display: grid;
  gap: 16px;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: masonry;
}

.card {
  background: #eee;
  border-radius: 8px;
  padding: 20px;
}

.short { height: 150px; }
.medium { height: 250px; }
.tall { height: 400px; }

In the old world, the browser would force Row 1 to be as tall as the tallest item (the 400px one), leaving a 250px gap under the short item. With native masonry, item #4 just tucks right up under item #1. No gaps. No JavaScript. No math.

Controlling the Flow

The spec also introduces masonry-auto-flow. This is where you get to decide if you want to prioritize the DOM order or if you want the browser to fill every single hole perfectly, even if it means moving item #10 before item #9.

.container {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: masonry;
  
  /* The browser tries to fill gaps as efficiently as possible */
  masonry-auto-flow: pack;
}

If you use masonry-auto-flow: ordered; (which is usually the default), the browser will maintain the source order. This is vital for accessibility. Screen readers follow the DOM, and if your visual layout matches that order, you’re not confusing users who rely on tab-navigation.

The Catch (And there’s always one)

I know what you're thinking: "Can I use this today?"

The answer is: Almost.

Currently, this is behind a flag in Firefox and is being actively developed in Safari (WebKit). Chrome/Blink has been a bit of a holdout because there’s an ongoing debate about whether masonry should be part of the CSS Grid spec or its own separate display type (like display: masonry).

How to test it right now:
1. Open Firefox Nightly.
2. Go to about:config.
3. Set layout.css.grid-template-masonry-value.enabled to true.

Why you should care anyway

Even if we can't ship this to 100% of users today without a polyfill, it signals a massive shift in how we approach web performance. We are moving away from the "JavaScript-as-a-crutch" era of layout.

When this hits the mainstream, your "Heavy Image Gallery" page weight will drop. Your Time to Interactive (TTI) will improve because the main thread isn't busy calculating pixel offsets. Most importantly, the layout will be handled by the browser's C++ engine, which is orders of magnitude faster than any script you could write.

My Advice?

Stop building new projects that rely heavily on Masonry.js if you can avoid it. If a staggered grid isn't "mission critical" for the brand, consider using a standard CSS Grid with object-fit: cover to keep things clean.

If you *must* have masonry, start looking at CSS-only alternatives like column-count (with its caveats) or prepare your codebase to switch to the native spec as soon as it hits the "Baseline" status.

Native masonry is coming to save our bundles—and our sanity. It’s about time.