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

The Alt tag is a concept that people outside the field would find hard to picture when they come across it. People who work in content or advertising know a little about it. This article will help you better understand what the Alt tag is and how to create an SEO-optimised image Alt tag. Let's MONA Media find out in the article below!

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. This includes browsers that block images and screen readers, and especially users who are visually impaired or cannot recognise images visually. In detail, it covers your alternative text and images, so that all Internet users, whatever their visual ability, can appreciate your website's content.

2. Image SEO

Using alternative text on images can give visitors a better experience, and you also gain benefits for SEO in ways that are both hidden and obvious. Writing good image titles and file names, including alternative text, contributes 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.

In this respect, alternative text gives you another chance to include your target keyword. To add weight by using keywords as a search engine ranking factor, you should create an Alt attribute that both describes the image and includes a few keywords or key 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. Optimising 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 the MONA team had the chance to work on, helping the client reach the TOP of Google. Thanks to a tailored optimisation 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 note 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.
• Prioritise 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 optimising images in an article.

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Detailed guide to optimising Alt tags for SEO

The Alt tag also needs optimising, and optimising it as naturally as possible will give you great results. Let's look at how to optimise Alt Tags for SEO below:

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 tag for an image is actually very simple; almost anyone can do it after looking it up or being shown once. Today, most websites have a built-in way to add 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.

Optimising the Alt tag is an important, essential factor that has a real effect on your website's SEO performance. So don't skip this image optimisation step!

Did you know that up to 1/3 of a website's organic traffic comes from Google Images? In visually driven fields like fashion, cosmetics, furniture, food or travel, each image is not just an illustration; it can also become a “magnet” for organic traffic if optimised correctly. Because we understand that value, MONA Media offers full-scope SEO services that help businesses make the most of this sustainable and completely free source of traffic.

At MONA, we don't just focus on pushing keyword rankings; we aim for a comprehensive SEO strategy, optimising every factor from content and technical aspects to user experience.

Highlights of full-scope SEO services at MONA Media:

• Thorough analysis of the current state and quality of the website
• Research and delivery of a suitable keyword set with high conversion potential
• Optimize SEO Onpage – Offpage – Technical – Image SEO – comprehensive AI SEO
• Ensuring SEO-standard content, images, videos and links
• Raising the website's authority score (DA) and trustworthiness
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• A team of experts with you 24/7, committed to clear and transparent results

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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 to check.

MONA suggests 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 optimise: the image file name.

5. How to name images

You can name images however you like, but if you want to optimise 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, colours 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.

Above are the criteria for you to optimise 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!