DEV Community

Cover image for A hitchhikers guide to web images on 2019
Jaime Rios
Jaime Rios

Posted on

A hitchhikers guide to web images on 2019

Cover photo by JfXie

The goals of this post is to give you some exposure to the current web capabilities and help you identify some opportunity areas for:

A few assumptions about you reading this post:

  • You are familiar with HTML.
  • You know basic image formats like jpg, png and svg.
  • You are somewhat familiar with CSS and enough have enough expertise to read, understand and implement the MDN documentation.


The web is evolving, fast. Nice to have features have become something you as a developer, are expected to be familiar with here are some that are common:

  • Internationalization (i18n).
  • Front End Routing.
  • Responsive web design.
  • Front End User Authentication.
  • SEO.
  • Page Speed Optimization.

New features within the HTML spec

The HTML5 spec, is intended to serve a mobile web, you can think of it as two things a set of HTML tags, and several new APIs

Let us revise some new tags and attributes one by one, after that I will add an example that uses all of these.


You can think of it as an img tag with more flexibility to display image resources. It allows us to provide higher-density versions of an image to high-DPI displays. Let us see what it looks like, according to MDN:

The HTML element contains zero or more elements and one element to provide versions of an image for different display/device scenarios.


The HTML <source> element specifies multiple media resources for the <picture>, the <audio> element, or the <video> element.

srcset attribute

This attribute is similar to src, but used to define multiple images src, there are many ways to implement this sources

Declare the attribute once with multiple images and a src as a default. Check original source at

  srcset="image-1x.png 1x, 
          image-2x.png 2x,
          image-3x.png 3x, 
          image-4x.png 4x"
Enter fullscreen mode Exit fullscreen mode

The other way is to declare multiple sources and within each have one srcset. You can see it in the example below. The main difference is that the second has a more specfic conditions for image displays.

Putting it all together:

See it on Codepen

  <source media="(max-width: 799px)" srcset="">
  <source media="(min-width: 800px)" srcset="">
  <img src="" alt="A cute black cat showing his love">

Enter fullscreen mode Exit fullscreen mode

New relevant CSS properties

In case you did not know, spoiler alert, CSS 4 does not exist. Instead we have small increments being supported by modern browsers. Here are some properties that is good to be aware of:


As the name suggests, object-position, defines the way in which an object is defined within a box. It is quite similar to background-position. You can see the code pen example in, thanks @Robin Rendle.


This property serves to tell the browser how it should render the image. The values describe the algorithm that will be implemented in order to scale the image, by the time of this writing, the possible values are:

  • auto: Default value, the browser's algorithm will determine how to scale the image.
  • crisp-edges: It preserves contrast and edges in the image.
  • pixelated: As the name suggests, the browser will keep it's pixelated style as the viewport grows.

You can see how this three images behave in this example on Codepen.

Or check this image-rendering applied to a QR code.

Image formats

<img alt="Apple iPhone 7 Plus, GSM Unlocked, 32GB - Rose Gold (Refurbished)" src="" class="product-image" height="200px" data-a-hires="">
Enter fullscreen mode Exit fullscreen mode

Lazy loading

Lazy loading images means that they are served slowly and it is avoided until it is necessary.

When implemented, for the final user it usually means a smaller bundle served, faster loads and a better experience overall.

Intersection Observer API

For starters, you might want to use the Intersection Observer API.

Simply put, the API provides users a way to observe given elements and monitor changes in their intersection with a given ancestor element, or the viewport itself.

If you use Gatsby, Gatsby Link is already using it under the hood.

For modern frameworks here are some npm packages you might want to look into:


Even when you have lazy loading in place, user's internet speed might be slow or interrupted, even in urban areas, even if the user is not aware of it, so it is good to have something in place to the user to see. That's where skeletons come in place.

A skeleton is a placeholder in a place which need waiting for loading

You might have seen it before, this is what a skeleton looks like:

alt text

There are some npm packages you might use in order to implement this feature, but as a rule of thumb, let's use something simpler.

Introduce :empty pseudo-class

According to MDN Docs:

empty represents any element that has no children. Children can be either element nodes or text (including whitespace). Comments, processing instructions, and CSS content do not affect whether an element is considered empty.

So an skeleton can be as simple as

 * ...your styles

.user-data:empty {
  background: rgba(130, 130, 130, 0.2); 
Enter fullscreen mode Exit fullscreen mode

You can check an animated Skeleton Screen with CSS or :empty at MDN Docs.

Introduce WebP

WebP is an image format designed for the web, it was released on September 2010 and other than Safari, now it is widely supported on most modern browsers. If you check your profile picture on, you might find that it is already using it. I'll list a few articles in the last part.

Further resources

That's all folks, thanks to making it to the very end, keep on learning.


Top comments (6)

fatimatariq25 profile image
Fatima Tariq

Hey Jaime, nice article, well described. You have just saved me. I was looking for something like this. I need to boost up my page and for that, I need to optimize my images. I was searching for some easy tips and ways. Thanks for sharing.

papaponmx profile image
Jaime Rios

I'm glad to help.

misnina profile image

I have to say I honestly knew none of this before your post! Thank you for sharing. : )

papaponmx profile image
Jaime Rios

I'm glad you found it useful πŸ™πŸ˜¬

gabrielski profile image

"srcset" is so handy! Thank you for sharing!

papaponmx profile image
Jaime Rios

Thanks for taking the time and attention to check it out