Alt texts (or alternative texts) are concise descriptions added to the HTML code of images, essential for SEO optimization and accessibility. They help search engines like Google understand visual content and, at the same time, allow visually impaired people to access information through screen readers. Thus, they have a dual role, at the intersection of technical and human.
Although it seems like a minor detail, correctly optimizing this attribute can generate additional traffic from Google Images, improve the semantic relevance of pages, and make your site more inclusive. In this complete guide, we will dismantle the process from A to Z, with clear examples and strategies you can apply immediately.
What is an Alt Text (Alternative Text)?
Alternative text, technically known as the `alt` attribute, is a piece of text added to the `` tag in the source code of a web page. Its fundamental purpose is to provide a textual alternative for an image, in case it cannot be rendered by the browser (due to a poor connection, a server error, or user settings) or cannot be "seen" by the user (in the case of people using assistive technologies).
Essentially, the `alt` attribute is the translation of an image into words, a bridge between visual content and algorithmic or assistive understanding.
In HTML code, it looks like this: <img src="image.jpg" alt="image description">. The text between the quotes of the `alt` attribute is what we optimize. Although invisible to most users under normal conditions, its impact on a site's performance is significant.
Why is alternative text crucial in present? Roles and Benefits
The importance of alt text has constantly grown, evolving from a simple technical recommendation to a central pillar in SEO and accessibility strategies. Ignoring it means losing valuable opportunities. Here are its main roles:
1. Web Accessibility: A Foundation for Inclusion
This is the primary role. Visually impaired people use screen readers to navigate the internet. When such software encounters an image, it reads aloud the content of the `alt` attribute. A descriptive and precise alt text allows these users to understand the context and information conveyed by the image, ensuring an equitable experience. According to WCAG (Web Content Accessibility Guidelines) standards, completing the `alt` attribute is a Level A conformance requirement, meaning it is essential.
2. Semantic Relevance for SEO
Search engines, although they have advanced enormously in the visual interpretation of images through multimodal AI (like Google Gemini), still rely on textual signals to understand the complete context. Alt text provides a direct and strong clue about the image's content. When the description includes relevant keywords for the page, Google better understands the connection between the text and visual elements, strengthening the page's topical authority and helping it rank better in organic searches.
3. Performance in Image Searches (Google Images)
Google Images is one of the largest search engines in the world. For many niches (e-commerce, culinary recipes, design, tourism), traffic from image searches is substantial. A well-optimized alt text, along with a descriptive file name and a quality image, exponentially increases the chances of your images appearing in relevant results, attracting qualified visitors directly to your site.
4. Improving User Experience (UX)
What happens when an image doesn't load? If the `alt` attribute is empty, the user sees an empty box, an unsightly error that creates confusion and frustration. If the alt text is filled in, the descriptive text will be displayed instead of the image. Thus, the user understands what they should have seen, the context is not lost, and the experience remains positive. This small detail contributes to lowering the bounce rate and keeping users on the page.
5. Context for Image Links
When an image is used as a link (it is surrounded by an `` tag), the image's `alt` attribute functions exactly like the anchor text for a textual link. Search engines use this text to understand what the destination page is about. A descriptive alt text in this context is crucial for correctly passing SEO relevance and authority to the linked page.
How to write a perfect Alt Text: A 7-step guide
Creating effective alternative text is more of an art based on simple SEO rules than a complicated science. Follow these steps to ensure that every image on your site contributes to your goals.
Step 1: Be descriptive and objective
Start by describing what is in the image as objectively as possible. Imagine explaining the photo to someone on the phone. Focus on the main subject, important actions, and relevant context. Do not interpret or add information that is not visually present.
- Weak: `alt="woman at desk"`
- Good: `alt="Woman smiling while typing on a laptop in a modern office."`
- Excellent: `alt="Marketing manager analyzing a performance chart on a laptop screen."` (if the page context allows specificity)
Step 2: Keep it concise (ideally under 125 characters)
Although there is no strict technical limit, most screen readers stop reading after about 125 characters. To ensure an optimal experience for assistive technology users, try to convey the essential within this range. Be specific, but eliminate filler words. Clarity beats length.
Step 3: Integrate keywords, but without abuse (No Keyword Stuffing)
If it is natural and relevant, include the page's main keyword or a synonym in the alt text. This strengthens the SEO signal. However, avoid over-optimization at all costs. Correct use of alt text is about relevance, not keyword stuffing. Google penalizes "keyword stuffing" practices.
- Context: A blog post about "SEO agency costs".
- Incorrect (Keyword Stuffing): `alt="costuri agenție SEO prețuri SEO servicii SEO ieftine București"`
- Correct: `alt="Comparative graph of monthly costs for an SEO agency in YEAR."`
Step 4: Avoid redundant phrases
There's no need to specify that it's an image. Screen readers and search engines already know this from the `` tag. Phrases like "image of...", "picture about...", or "photograph of a..." are redundant and consume precious characters. Get straight to the point.
- Incorrect: `alt="Image of a golden puppy playing in the park."`
- Correct: `alt="Golden retriever puppy running after a ball in a sunny park."`
Step 5: Correlate the text with the page's context
The same image can have different alt texts, depending on the article it is placed in. The description must serve the purpose of the page. For example, a photo of the Eiffel Tower can have distinct alt texts:
- On a travel blog: `alt="Eiffel Tower illuminated at night, seen from Trocadéro."`
- On an engineering website: `alt="Detail of the Eiffel Tower's steel structure, designed by Gustave Eiffel."`
- On a photography website: `alt="Long exposure photograph of the Eiffel Tower, capturing the light trails of boats on the Seine."`
Step 6: Correctly manage decorative images
Not all images convey information. Purely decorative elements (section dividers, abstract backgrounds, design icons) should not have a descriptive alt text, as this would unnecessarily clutter the experience for screen reader users. In this case, the correct solution is to use an empty `alt` attribute: `alt=""`. This signals assistive technologies to ignore the image.
Step 7: Write for people, then for robots
After you've written an alt text, read it aloud. Does it sound natural? Is it useful? If a colleague were to read only this description, would they understand what the image is about? If the answer is yes, then you've created an effective alt text for both people and search engines.
Common Mistakes in Writing Alternative Texts (and How to Avoid Them)
Optimizing alternative texts is a simple process, but prone to errors. Here are the most common mistakes we see when auditing websites and how to correct them:
- Complete absence of the `alt` attribute: The most serious error. Every image that conveys information must have an alt text. SEO audit tools like Screaming Frog can quickly identify all images without alt text.
- Keyword Stuffing: Forced repetition of keywords. Creates a negative experience and can be penalized. Focus on a natural description.
- Generic texts: File names (e.g., `IMG_8374.jpg`) or texts like `„logo”` offer no value. Be specific: `„Danco Vision Logo - full-service SEO and performance agency”`.
- Overly long descriptions: Texts exceeding 150-200 characters can be truncated by screen readers. Detailed information should be in the main body of the article or in the caption.
- Using the same alt text for different images: Each image is unique and deserves its own description, even if the subject is similar. Vary the descriptions to reflect subtle differences.
- Confusing the `alt` attribute with the `title` attribute: These have different roles. Alt text is for accessibility and SEO, while `title` displays a small tooltip on mouse hover and has negligible SEO impact.
How to optimize Alt Texts at scale: Tools and Strategies
For a website with thousands of images, manual optimization can seem like a colossal task. Fortunately, there are tools and strategies that can automate and streamline the process.
CMS Plugins (WordPress, Joomla, etc.)
Most modern CMS platforms facilitate the addition of alt texts. In WordPress, for example, you can add alternative text directly from the Media Library or while editing a page. SEO plugins like Yoast SEO, Rank Math, or All in One SEO offer audit functionalities that warn you if you have images without alt text in your content, simplifying the identification and correction process.
AI Alt Text Generators
Artificial intelligence tools can analyze an image and automatically generate an alt text proposal. Services such as those integrated into cloud platforms (Cloudinary, Imgix) or dedicated plugins can scan your media library and automatically fill in missing `alt` attributes. Although they are extremely fast and efficient for large volumes, the results must always be verified by a human. AI excels at objective description, but it cannot understand the strategic context of the page or the search intent.
AI can generate an alt text proposal in 0.2 seconds. The value of an SEO expert no longer lies in writing the text, but in strategically validating it. Is this alt text relevant to the search intent? Does it support the topical authority of the page? This is where human intelligence comes in, which still surpasses any automation. - Daniel Ionescu, Founder Danco Vision
Technical SEO Audit Tools
Software like Screaming Frog SEO Spider or Sitebulb are essential for a complete audit. These can crawl the entire site and generate detailed reports with all images that have missing, duplicate, or overly long alt text. You can export these lists and systematically work on correcting them, prioritizing pages with the highest traffic or potential.
Automations in E-commerce Platforms
Platforms like Shopify or Magento often allow you to create rules for automatically generating alt texts for product images. For example, the alt text can be generated using a structure such as [Product Name] - [Color] - [Brand]. As part of SEO optimization for online stores, this approach helps maintain consistency across large product catalogs, improve image optimization, and save valuable time.
How to Choose the Right Strategy? 5 Essential Questions
Before starting optimization, answer these questions to define your strategy:
1. What is the main role of images on my website? Are they informative (graphics, diagrams), product-related (e-commerce), illustrative (blog), or decorative? The answer dictates the necessary level of detail.
2. How important is traffic from Google Images for my business? For an online fashion store, it is vital. For a law firm, it may be less of a priority. Allocate resources based on potential impact.
3. What resources do I have available? Do you have time for manual optimization or do you need automated/outsourced solutions? Be realistic about your team's capacity.
4. Which are the most important pages on the site? Start optimization with pages that already generate traffic and conversions (top products, pillar articles, service pages) to see quick results.
5. How will I measure success? Monitor traffic from Google Images in Google Search Console (Search Type: Image), track rankings for visual keywords, and analyze accessibility scores with tools like Lighthouse.
FAQ - Frequently Asked Questions about Alt Text
Next Steps: Audit and Implementation
Now that you understand the strategic importance of alternative text, it's time to take action. Start with an audit, either with the support of an experienced SEO agency or by using tools such as Screaming Frog and the audit functionalities of your SEO plugin. This will help you identify images with missing or incorrect alt attributes and prioritize the necessary optimizations.
Prioritize your site's most important pages: homepage, service pages, top products, or blog articles with the most traffic. Manually correct the alt texts for these pages, applying the principles from this guide. For the rest of the site, you can use a combination of automated strategies and manual verification. Make alt text optimization a habit. Make it part of your publishing checklist for any new content. It's a small effort with a compounded impact over time.
