Adaptive Photo Layout with Flexbox

Use Flexbox to achieve adaptive photo layout, lightweight and efficient! This article introduces a lightweight approach to creating horizontal waterfall streaming photo layouts using Flexbox, enabling seamless arrangement of photos of any size without JavaScript.

This solution is not only lightweight, but also very simple. We only need an unordered image list and 17 lines of CSS code, and the core lies in the Flexbox and object-fit properties.

Why choose this method?

I have two hobbies: recording life with photos, and exploring interesting ways to combine CSS attributes (both new and old).

A few weeks ago, I attended the XOXO event, took a lot of photos, and finally filtered out 39 beautiful photos. To better manage my content, I have been trying to create a simple photo blog for the past few years, but I have never been able to achieve my ideal layout: a simple waterfall layout where photos fill lines while maintaining their aspect ratio (think Photos apps on iOS, Google Photos, Flickr…).

I did some research to see if there are any lightweight, non-JavaScript options, but couldn't find any solution that matched my needs. While waiting for flight delays, I started trying some code and restrict myself from keeping the code as concise as possible (because that's exactly what I think is the fun).

Basic HTML structure

Since I'm basically creating a list of images, I chose an unordered list:

<li> <li> <!-- ... more images ... -->

The wonderful uses of Flexbox

Then there are a series of moments of inspiration:

<li> Flexbox is ideal for filling rows by determining the cell width based on the content of the cell. <li> This means that all images (land or portrait) need to have the same height. <li> I can use object-fit: cover; to make sure the image fills the cells.

In theory, this sounds like a reliable solution, and it gives me a result that I'm 90% satisfied with.

ul {
  display: flex;
  flex-wrap: wrap;
}

li {
  height: 40vh;
  flex-grow: 1;
}

img {
  max-height: 100%;
  min-width: 100%;
  object-fit: cover;
  vertical-align: bottom;
}

Note: 40vh seems to be the best initial approach for desktop browsers, showing two lines of full photos at reasonable size and suggesting that there are more photos below. This also allows more photos to be displayed per line, which significantly improves aspect ratio.

Handle the last line of stretching issues

The only problem I've had is that Flexbox really wants to fill all the rows, and it does something weird about the aspect ratio of the last row of photos. This is probably my least favorite with this layout, but I had to add an empty one at the end of the list<li> element.

<!-- ... more images ... -->

<li>

Combined with the following CSS code:

li:last-child {
  flex-grow: 10;
}

Note: There is no scientific basis for using "10" here. This provides the best results in all my tests.

Demo (demo link or code snippet should be inserted here)

Viewport optimization

Some factors need to be considered when working in different viewport directions.

Vertical screen

If your viewport height is greater than width, this method limits the number of photos per row, affecting its aspect ratio. To solve this problem, you can use simple media queries to make the photo line shorter:

@media (max-aspect-ratio: 1/1) {
  li {
    height: 30vh;
  }
}

Shorter screen

To adapt to small horizontal devices, increasing the height of the photo can help to display the photo as large as possible:

@media (max-height: 480px) {
  li {
    height: 80vh;
  }
}

Smaller vertical screen

Most phones are not wide enough to get Flexbox to work properly without shrinking photos, so I chose not to try to hold multiple photos per line. Still, setting the maximum height here is worth it so you can at least get a glimpse of the next photo on the list.

@media (max-aspect-ratio: 1/1) and (max-width: 480px) {
  ul {
    flex-direction: column; /* Change to column direction*/
  }

  li {
    height: auto;
    width: 100%;
  }

  img {
    width: 100%;
    max-height: 75vh;
    min-width: 0;
  }
}

Summarize

This approach doesn't completely respect the aspect ratio of the photo (but is already close) and occasionally leads to some weird results, but I absolutely love its simplicity and flexibility. Want to get your gallery to scroll horizontally instead of vertically? Just make some adjustments. Is there 1,000 photos in the gallery or only one? All look good. Not sure about aspect ratio? Flexbox is your best choice. If you haven't viewed the demo yet, please read it again and let me know what you think!

Additional Tips

Depending on the size of these photos, such pages may grow to several megabytes very quickly. In my blog, I added loading="lazy" to solve this problem. With this property, images will only load when you are close to them as you scroll. Currently it is only supported in Chrome, but you can write a more widely supported technology yourself.

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