When to optimize the alt text of existing images… and when not to.

When you use an SEO tool like Ahrefs or SEMrush or a crawler like Screaming Frog to analyze your company’s SEO performance, it will more than likely tell you to optimize the alt text of your existing images.

But should you?

As is often the case with SEO, it depends.

This article explains when old images deserve your attention and when they don’t.

We also show you best practices to follow when uploading new images to your site so you won’t have to worry about them again in the future.

What are image alt tags?

The image alt text, also referred to as the image alt tag, is “alternative text” that describes images to people who are unable to see them. That includes users who are visually impaired and who use screen readers but also people who are using browsers that block images or those whose internet connection is not strong to load images. As such, image alt text is an important component of accessible web design.

Aside from that, image alt text allows search engines to better crawl your images, understand what they’re about, and thus index and rank them. 

When you’re looking at the HTML of an image depicting an extract from an online language course, for example, it could look like this:

<img src=”spanish-vocabulary-exercise.jpg” alt=”spanish vocabulary exercise example from course”>

Img alt tag best practices

An image alt tag that is optimized for both users and search engines follows these guidelines:

  • It’s specific. Describe the image keeping in mind that the user can’t see it.
  • It’s short. Many screen-reading tools stop reading at 125 characters so that’s a good limit to aim for.
  • It doesn’t say it’s an image. Search engines and screen readers know this thanks to the HTML so there is no need to start your description with “image of…”
  • It’s not stuffed with keywords. Ideally, you’ll add your focus keyword to one of the images on your page in a natural way. Don’t add it to every alt tag.
  • It has an empty alt tag when purely decorative. Icons and other purely decorative elements shouldn’t get alt text. In these cases, it’s best to add an empty alt tag as some screen readers will read the file name if there is no alt tag present. When the alt tag is empty, they will just skip it.

Should you invest time optimizing the image alt tags of existing images on your site?

Yes, when …

… you want to rank in Google Images

If you are selling a B2B SaaS application for enterprise communication, there probably won’t be a lot of people looking for your product in image search, but if you’re an e-commerce brand selling shoes, that’s a different story.

You can consult Google Search Console to check whether you are already getting traffic from image search or not.

These are the settings you’ll want to use:

… your old images are slowing down your site

Unless you’re trying to rank your images in Google Search, the only reason to spend time on existing images is when they are slowing down your site, as page speed is a crucial ranking factor.

When it comes to optimizing the size of existing images, there are two scenarios:

1. Your images still have their original resolution. In this case, you will first need to download the images and change their dimensions. If your website content is only 800 pixels wide, your images shouldn’t be their original 4032 pixels wide.

Next, either use an off-site compression tool like tinypng before you upload the images to your site again or a plugin like ShortPixel that optimizes as you upload them.

As you’re uploading these images, check that their filenames are descriptive (for example “spanish-vocabulary-exercise”) and not something like DC45826. And as you’ll need to fill in their meta info again anyway, this is one occasion where it makes sense to also create a good alt tag.

2. Your images already have the correct resolution. In that case, you can use a plugin to bulk-optimize your old images and make sure they’re as lightweight as possible. 

No, when … you can do something more effective!!!

Unless you can get a lot of additional traffic from Google Images or your current images are slowing down your website, optimizing hundreds of already uploaded images probably won’t make a big difference to your SEO performance.

The time your team saves by not worrying about old images can be spent creating keyword-researched articles or sending outreach emails for backlinks instead.

Backlinks and in-depth content are some of the most powerful ranking factors. 

This has been proven by many correlational studies, one example is the well-known study from Brian Dian

When marketers and SEOs see the image issue within their automated SEO audits, they sometimes get side-tracked and spend a lot of time on image alt tags.

But in the end, you want to rank. And we know you could be spending your time better.

And so, instead of spending 10 hours on optimizing thousands of old images, you could be creating two keyword focus blog posts that drive relevant new traffic – or discuss a PR opportunity that leads to powerful backlinks.

These tactics are much more likely to move the needle… and your rankings. We know this is true for most of our software clients.

Optimizing alt text: Look forward, not backward

While new images should be uploaded with optimized alt tags, changing the alt tags of existing images is only worth it in two cases:

  1. When you’re trying to rank in Google Images.
  2. As a side gig when optimizing image file size

In all other cases, you’ll get better SEO results having your team spend its team on the creation of rankable content or on building backlinks.

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Author: Viola Eva

Viola is passionate about digital entrepreneurship, flow, and mindful marketing. As a marketing consultant and SEO, she has worked with clients ranging from individual digital entrepreneurs to software companies to multi-national corporates and government institutions. She is a speaker, educator, and specialist on all things SEO.