What Is an Alt Tag? A Guide to SEO-Friendly Image Alt Text

The Alt tag is a term most people outside the industry have never heard of, though anyone working in content or advertising knows a bit about it. This article explains what the Alt tag is and how to write an image Alt tag that is optimized for SEO. Let’s MONA Media get started.

What is the Alt tag?

The Alt tag is an abbreviation of the phrase Alternative Information (understood as “alternative information”). Other names for the Alt tag are Alt Tag, image Alt description or the Alt attribute in the img tag. It is used as a short text describing the content of the image.

The Alt tag in HTML helps Google understand what the image is about, so it can return more accurate results to users. Also, in cases where the image cannot be displayed, users can still understand what the article is saying about the image through the Alt Text.

Put simply, the Alt tag appears in place of an image on a page to describe it to readers who visit the website but cannot see what the image is. The image Alt attribute is considered one of the important factors in SEO Onpage though not as important as keywords, SEO titles and descriptions.

-> See more: How to write the tag Meta Description SEO-ready

Why does Alt Text matter for SEO?

1. Better accessibility

Alternative text is an important factor in website design. The main purpose of Alt Text is to describe images to visitors who cannot see them. That includes browsers that block images, screen readers, and especially users who are visually impaired or cannot recognize images. Good alt text means every internet user, whatever their eyesight, can make full use of your website’s content.

2. Image SEO

Alternative text gives visitors a better experience, and it also helps your SEO in ways both subtle and obvious. Good image titles and file names, together with alternative text, all contribute to your image SEO.

Although search engines' image recognition technology has improved a lot in recent years, search crawlers still cannot “read” images on a website the way we can.

That is why we should not leave this interpretation to the search engine. If it misreads the image or doesn't understand it at all, you may miss out on rankings completely or rank for keywords you didn't intend.

Example: Google may be able to see the image above and decode it as a man and a girl holding pictures. But if you want to rank for the keyword “thiết kế website bán hàng trực tuyến” (online store website design), you need to help the search engine understand the image by writing the most relevant Alt Text possible.

Alt text also gives you one more place to include your target keyword. Since keywords are a ranking factor, write an Alt attribute that describes the image and includes a few of the keywords or phrases you are targeting.

Many businesses invest heavily in website content and images but overlook the ALT tag, a small detail with a big impact. Without the ALT tag, Google cannot understand what your image is trying to convey, which means the website loses the chance to appear on Google Images, a potential source of organic traffic. SEO is not just about writing articles or good-looking design; you also need both users and Google's bot to “understand” your value. Optimizing every small detail is the core principle Agency SEO – MONA follows when delivering full-scope SEO for clients' websites.

Explore the case study MONA x Bình Mỹ Elderly Care System, one of the standout projects where the MONA team worked alongside the client to reach the top of Google. Thanks to a tailored optimization strategy built around the website’s actual condition, Bình Mỹ exceeded its targets and got 100% keywords into Google's top search results.

Things to keep in mind when using Alt tags

To get the most out of the Alt tag, keep the following points in mind:

• It should contain keywords but not be deliberately stuffed, because Google dislikes this, and you also risk Google mistaking it for spam Anchor Text.
• Don't write overly long ALT Text; keep it short and focused on the main topic.
• Prioritize the main elements such as the title and description over the Alt tag, unless the article's main content is images.

-> See more: What is image SEO? How to do image SEO effectively

The difference between the Alt tag and the image Title

Many people mistakenly think the Alt tag and the Image Title are the same. In fact, they are two completely different things.

Specifically, the image Title is just Additional Information for the image, and it should always be short. However, the Image Title content is not displayed if the image fails to load. Conversely, readers can see the Alt attribute if they hover over the image.

The Alt Tag and the Image Title are added to article content in two different ways. But both are important additions for optimizing images in an article.

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Detailed guide to optimizing Alt tags for SEO

The Alt tag needs optimizing too, and the more natural the optimization, the better your results. Here is how to optimize Alt tags for SEO:

1. Structure of the Alt description tag

The general structure of an Alt Tag is: <img src=”url” alt=”some_text”> or written out in plain words: <img src=”link to the image file” alt=”description” />

In the img src part, add the link to the image file you want to display. In the Alt attribute, you can write any content for the image. However, it must still meet the criteria mentioned above for Alt Text.

Or if you want to add an Image Title to the image, you can follow this structure:

<img title=”image title tag” src=”image link” alt=”image alt tag” />

The title tag is optional, but Alt is the part Google recommends we use.

2. How to write Alt Text for images

Writing a description for an image is actually very simple; almost anyone can do it after looking it up or being shown once. Most website platforms today have a built-in field for adding Alt to images.

You can go to your website's media library and click on an image. Each image has fields for the Alt tag, title tag and description tag for you to fill in. All you need to do is fill them in sensibly and follow the steps the website asks. That's it, you've added Alt Text to the image quickly and easily.

If the website doesn't have this function yet, it is a job for a website developer. They will modify the website's code using the structures shown above. Once they edit and update the system, the image Alt attribute field will appear and you can use it.

Optimizing the Alt tag is an essential step that has a real effect on your website’s SEO performance, so don’t skip it.

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3. How to check whether images have the Alt attribute

There are many ways to check whether images on a website have Alt tags. Use a website checking tool or install dedicated software.

We recommend the tool SEOptimer. It is very easy to use: just enter the URL of the website you want to check and click check. Image Alt Tag Checker gives you results within seconds, including: the number of images on the website, the number of images missing Alt, and the names of the images missing Alt.

4. SEO requirements for the Alt tag

• Alt Text content should be around 225 characters. It shouldn't be too short or too long, but should still sum up all the necessary content.
• You can write whatever you like, but our advice is to write Vietnamese with diacritics and with spaces (for example, if you want to write: Cây xanh đổ ngổn ngang trên quốc lộ 1A (Trees fallen all over National Highway 1A), don't write: Cay-xanh-do-ngon-ngang-tren-quoc-lo-1a).
• The main keyword should be placed in the first characters of the tag.
• Don't stuff keywords into Alt Text, because Google will assume you are spamming and push your article out of the top search results.
• The image for the tag must be high quality, not blurry, and not an image copyrighted by someone else.

These are simple criteria, but they make your article easier for search engines to crawl. Besides the Alt tag, there is one more thing to optimize: the image file name.

5. How to name images

You can name images however you like, but if you want to optimize them, pay attention to the following:

• Write image names without diacritics, with each word separated by a hyphen.
• Length under 125 characters.
• Contains the main keyword.
• Avoid generic names like: Hinh-1.jpg, anh.png, 1.jpg…

The reason you should write image names without diacritics or spaces is that servers often use the UTF-8encoding. When you first upload, there may be no problem, but when you backup (back up) to move to another server, the image names get re-encoded.

At that point, keywords with diacritics and spaces are automatically converted to UTF-8 escape characters. Of course you can rename them, but with many images it takes a lot of time to rename them all.

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Frequently asked questions

1- What information can the ALT tag contain?

The ALT tag can contain a description of the image content, including details such as subjects, colors and activities taking place in the image. It can also contain keywords related to the content and purpose of the web page.

2- Can the ALT Tag be used on elements other than images?

Although the ALT tag is most commonly used with the <img>tag, it can also be used on some other elements such as <area> and <input>. This helps provide descriptions for interactive elements and supports accessibility for users with disabilities.

3- Is there an optimal length for ALT Text?

There is no specific optimal length for the ALT tag. However, try to write a short, complete and accurate description of what is visible in the image, so users can understand the image content without reading too much.

Those are the criteria you need to optimize Alt tags for SEO and things to keep in mind when adding image Alt attributes. Your article can rank higher in search engines if it meets all the image ALT Text SEO criteria introduced in this article. Good luck!