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SEO for Growth

Behind the Scenes: Improve Indexability with Alt Text Optimization

Want images to index quickly? Here is a guide on how alt text optimization improves indexability and how to write alt text like a pro. Learn more here.

5 mins read time
Haley Kuehl
Haley Kuehl

Sep 16, 2022

On-page optimization is a gigantic task, as there are many things to do and manage. All types of content on your website need to be optimized for search engines and readers. Images are no different. Alt text optimization is much more than an ordinary on-page SEO tactic. It improves UX, accessibility, and relevance, and it is linked to the indexability of your website.

When used correctly, an optimized and well-written alt description helps search engine crawlers better understand the image, index it, rank it, and serve it in SERPs.

So how do alt texts work in the background of your site, and how do they help indexation? Let’s find out.

Why Alt Text Optimization Matters

Alternate text (alt text, alt attribute, alt description, or alt tag) is the HTML code that describes the image on websites. The alt text isn’t visible to the users as it works behind the scene and addresses key areas, including indexability (and ranking) and accessibility.

Indexability and accessibility are more important than anything else.

Adding relevant alt text to images makes them understandable to search engine crawlers. An image that doesn’t have any alt text doesn’t make much sense and might suffer from delayed or no indexing by the search engine.

Your job is to make content on your website (including images) easy to understand for crawlers so they can add those images to relevant indexes and rank them in SERPs for relevant keywords.

Here is how crawling and indexing work:

how search engines work


Content meaning and relevance are the two key factors that are used by search engines like Google for ranking. Alt text optimization improves both and improves not just indexing but image ranking.

Alt text plays an integral role in improving your site’s accessibility, which refers to removing barriers that prevent interaction with your website. It ensures that your website is accessible to people with disabilities and restrictions.

In all such cases, when your image fails to load or when someone accesses your website from a device (such as a screen reader), the alt text is shown instead of the image (a reason why it is called alternate text).

Here is an example of how optimizing alt text will help people who access your site via a screen reader:


It also holds true when images fail to load. In such a case, visitors see alt text, so it must be meaningful and relevant.

How to Write Alt Text

Here are the best practices for writing optimized alt texts that crawlers can read and index your images correctly and quickly:

  1. Descriptive
  2. Concise
  3. Add keywords
  4. Accurate
  5. Avoid fluff

1. Descriptive

The alt text must describe the image and its content. This is the purpose of using alternate text in the first place. It should be written in a way that someone who can’t see the image could understand the image from its alt text.

Here is an example:



In the case of an abstract image that’s purely decorative, you can skip alt text as it isn’t possible to describe it. 

2. Concise

When you have to describe an image in its alt text, you are not supposed to write paragraphs. It needs to be concise yet crisp as there is a limit to how many characters you can add.

Moz recommends keeping the alt attribute under 125 characters. This isn’t a hard and fast rule, but a great idea to keep it short.

There are, however, instances when you can’t keep the alt tag descriptions short. For example, when you have a chart or diagram, you will need more characters to explain it. In such a case, you can use longdesc="…" to refer users to a text or HTML file with a detailed image description.

The longdesc attribute only works with screen readers where they can listen to the image description.

3. Add Keywords

An SEO best practice for writing optimized alt texts is to add your keywords.

This doesn’t mean you should add keywords randomly that don’t make sense. You need to add keywords to the alt text only if it makes sense and adds value.

You need to come up with LSI keywords relevant to your page and use them as alt texts. This helps you improve topical authority and relevance.

4. Accurate

Yes, alt text optimization requires accuracy.

If it is an image of a dog, alt text must have the word “dog.” Don’t try to stuff keywords unnecessarily in the alt description.

5. Avoid Fluff

There are certain words you are not supposed to write in the alt attribute, such as:

  • Image or image of
  • Picture or picture of 
  • Photo or photo of
  • Pic or pic of

It is understood that the alt text is for an image, so any words or phrases like these don’t make sense.

Improving Indexability Gets Easier with Alt Text Optimization

Google returns images for as much as 41.8 percent of queries. Here is what John Mu has to say about alt texts:


This means optimizing alt text is the key to ranking in images. If you want your images to rank for the right keywords in SERP features, you need to make sure your images are indexed.

And this is where alt text optimization takes the lead. Fill in the wrong alt text for an image, and it will rank for irrelevant keywords leading to poor UX and low CTR. 

Is adding alt text all you need to do to improve indexability?

Not really.

There are two things you need to do to ensure images and alt texts are crawled and indexed.

First, set all images as indexed. This tells search engines that you want your images to be crawled and indexed. If you are using a plugin for on-page SEO, make sure that all the images are set to index.

Second, you need to add images to the sitemap. This improves crawlability and indexing. If images are indexed but aren’t added to the sitemap, they might take forever to get indexed.

Not sure where to begin alt text optimization? We are just a click away.


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Haley Kuehl

After getting her start in teaching, Haley fell in love with SEO because it let her combine two of her favorite things: writing and getting nerdy with data and code. She now has more than 12 years of SEO and inbound marketing experience with clients ranging from small ecommerce brands to huge associations and SaaS companies.

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