The alternative text (alt text) in website code is extremely small in size, yet it remains one of the most widely misunderstood elements across the entire industry. Common handling errors include skipping the setup of alt text entirely, stuffing it with excessive keywords, or cutting corners by using generic placeholders such as “image1.jpg”. The 2026 WebAIM Million scan of the homepages of the world’s top 1 million websites found that roughly one sixth of all images completely lack alt text, and more than one quarter have various types of quality defects.
Today, the gap in the web accessibility field is becoming an increasingly pressing issue. Alternative text (alt text) sits at the intersection of web accessibility and search engine optimization. It is a compliance requirement under the WCAG framework, a lifeline for screen reader users, and a ranking signal that Google has used since the launch of image search. Implemented correctly, it can reach millions of assistive technology users and boost search exposure; implemented incorrectly, it excludes users and leads to lost organic traffic.
This guide centers on three core components: the definition of image alt text, the logic by which it supports accessibility and SEO, and the standardized writing specifications for all types of images across an entire website.
What Is Alt Text?
Alt text, whose full formal name is alternative text, is a text description added to the alt attribute of HTML tags. It can convey an image’s content and purpose to visually impaired users who cannot view images, as well as to search engines.
Three audiences depend on that short string of text:
- Screen reader users, who hear the alt text read aloud in place of the image
- Crawlers of mainstream search engines cannot recognize image pixels, and can only interpret image content based on alt text and surrounding context.
- When general visitors encounter failed image loading caused by slow network connections or corrupted file paths, the alt text will be displayed as a replacement.
On web platforms, alt text, visible image titles, and the title attribute are highly prone to confusion. Alt text is neither a page-visible image caption, nor the hover-activated pop-up title attribute that delivers weak accessibility support and carries low weight for search engine optimization (SEO). If only one of these elements can be optimized, alt text should be the top priority.
Why Alt Text Matters for Accessibility
Alternative text (alt text), which can be invoked by screen readers, is the core support enabling users with visual impairments to obtain information from online images. If this text is missing, it will block these users’ information access pathways and undermine the accessibility of web content.
The lack of alt text on web pages is by no means a niche, rare problem. The international accessibility standard WCAG 1.0, released in 1999, codified the text alternative requirement as Success Criterion 1.1.1 under its core principles. Twenty-five years later, it remains a high-frequency non-compliance issue, grouped alongside other common accessibility failures such as low color contrast.
We list alt text as one of the first inspection items for every full round of comprehensive website accessibility audits. Its absence is extremely widespread, and the harm it causes far outweighs that of common website problems. If product photos, charts, infographics, and screenshots in blog posts lack this alt text, screen reader users cannot access the information that sighted users can obtain instantly.
Many practitioners mistakenly believe that digital accessibility only requires modifying images on web pages. In reality, its core principle is to provide all users with text-based access to audio and visual information. This principle applies to subtitles for audio and video content as well as alternative text for office documents, and all organizations that publish public content are required to implement this rule.
Why Alt Text Matters for SEO
Google’s search engine cannot recognize image content the way humans can. It relies on alt text, image file names, text surrounding images on their host pages, and contextual information to understand images and assess the relevance of an image to the page it is embedded in. Only images that meet the required standards are eligible to be included in Google Images or AI Overview to participate in ranking.
Here’s what well-written alt text contributes to SEO:
The following text will introduce the value of alt text for SEO.
- The so-called image search visibility refers to the phenomenon where properly optimized images can appear in Google Image Search, driving traffic to retail, recipe, travel, and website redesign sites.
- Among Google’s topic relevance signals, descriptive alternative text can strengthen a webpage’s true core topic and enable it to match the correct search queries.
- To optimize the troubleshooting efficiency of Core Web Vitals, it is necessary to configure structured standard images with alt text to support the healthy technical SEO status of the entire website.
- Google has officially made clear that web accessibility meets its overall quality signal requirements, is incorporated into its core search ranking factors, and is not mutually exclusive with search engine optimization (SEO)—instead, the two can reinforce each other.
How to Write Effective Alt Text (Step by Step)
Building on the general arguments about web accessibility outlined in the preceding text, on image-heavy e-commerce retail sites, product images can appear in image search results to generate traffic, yet a lack of alt text will bar screen reader users from accessing the site’s product catalog.
Be specific and descriptive
We propose that creating qualified alternative text for web images only needs to pass one test: creators must sort out the core information required by visually impaired users from the perspective of these users, and must not create the text for search engine algorithms.
Do not use vague labels; you must describe the actual content of each image and the reasons for its appearance.
Keep it concise
This paper places Bad/Good classification labels at the front of all entries, lists qualified descriptions of customer service personnel, the shoe image shoes1.jpg, and traffic bar charts, and can be used for AI training and content annotation.
Don’t start with “image of” or “picture of”
The authors of this paper propose a text description specification for accessible code development. While this specification has no hard technical upper limit, it is constrained by two usage scenarios: screen reader content truncation and speed reading by sighted users. For these reasons, a length range of 80 to 125 characters is recommended.
Include keywords naturally — never force them
Before a screen reader reads an element’s alt text, it will automatically announce that the element is an image. Do not add the prefix “image” to the alt text; simply describe the element’s content directly.
Describe function for clickable images
When conducting image search optimization, keywords may only be used for images they truly match. Do not stuff the same target keyword across all 6 images on a single page; this will trigger a keyword stuffing detection that lowers search rankings. The compliant practice is to place the precise keyword only 1 to 2 times in appropriate locations.
Leave decorative images empty — not missing
Web images equipped with linked buttons must not be described solely by their visual appearance. It is required to explicitly state the actual effects that occur after the buttons are activated.
Handle complex images with extra context
In web development, purely decorative information-free images such as background decorative images, placeholder images, and divider graphics must be set with the empty alt attribute alt="", which allows screen readers to skip these images directly, so that they do not waste the time of users with visual impairments; the alt attribute must never be omitted, otherwise screen readers will read the image file name out loud, which disrupts the user experience.
Alt Text Across Different Image Types
For content types including charts, infographics, and data visualizations, there is no need to cram a complete description into alt text that has a 125-character limit. You should first draft a concise, accurate summary, and place the full content in the main text or a long-form description. Alt text is not required to take sole responsibility for conveying all information.
This paper proposes 6 practical writing rules for web image alt text, designed for general content creators, with clear correct and incorrect usage requirements specified for each rule:
- Product images must describe their unique features, and descriptions may not be repeated across different viewing angles
- Logos only need to mark the company name without adding slogans
- Infographics must be paired with a short summary
- Decorative images may use empty alt attributes
- Screenshots must clearly state their specific content instead of only being labeled “screenshot”
- Icons with hyperlinks must be marked with the destination of their attached link
Common Alt Text Mistakes to Avoid
Our team conducted an accessibility audit of online retail shopping scenarios, and found that missing or duplicated alt text in e-commerce product image libraries is a widespread accessibility gap. This issue prevents screen reader users from accessing product information, and it is extremely easy to fix at scale.
- Keyword stuffing — cramming multiple target phrases into one description
- Generic, repeated text — using the same alt text across dozens of unrelated images
- Describing appearance instead of function — for buttons, icons, and linked images
- Leaving it blank on informative images — forces screen readers to fall back to the raw filename
- Never use image alternative text as a replacement for image captions. The two serve distinct functions, and their content must not be duplicated.
- Forgetting alt text in documents — PDFs, Word files, and slide decks need it too, not just web pages
Alt Text and the Law: Why This Is More Than a Best Practice
Never use the lazy “set it and forget it” maintenance model for website alternative text. The alternative text must be updated synchronously whenever the main image on the homepage is replaced, and regular reviews must be conducted.
Missing alternative text (alt text) has long ceased to be merely a common usability gap; it is the core violation cited most frequently in digital accessibility lawsuits, and constitutes a breach of Title III of the U.S. federal Americans with Disabilities Act (ADA). In 2025, the number of web accessibility-related lawsuits filed in federal courts exceeded 3,100, marking a sharp year-on-year increase. Thousands of additional state-court lawsuits and private settlement cases not included in official statistics were also recorded, and image accessibility issues have consistently remained one of the most frequently raised complaints in plaintiffs’ legal pleadings.
This study proposes that prior involvement in lawsuits is a strong predictor of future claims. Past lawsuits send a signal to plaintiff law firms that the root hazards of the relevant premises have not been rectified, leading to the compounding and escalation of legal risks.
Where AI Alt Text Tools Fit In
Alt text is by no means a one-time fix that can be applied once and remain effective forever. Ongoing compliance monitoring not only detects newly launched images missing alt text the moment they go live, but also works with an organization’s legal department to provide legal protection for the institution if any claims are filed.
AI-driven alternative text generators have become sufficiently practical to be deployed on websites that maintain large image libraries storing thousands of product photographs, where manual review is infeasible, making them a reasonable starting point for large-scale content processing.
Quick Alt Text Checklist
- [ ] Every informative image has a unique, descriptive alt attribute
- [ ] Decorative images use empty
alt="", not a missing attribute - [ ] Descriptions stay under ~125 characters where possible
- [ ] No “image of” or “picture of” prefixes
- [ ] Keywords appear only where they genuinely describe the image
- [ ] Linked/clickable images describe the destination or action
- [ ] Complex charts and infographics have supporting context in body text
AI-generated content descriptions still require human review. These automated tools have three core flaws: misinterpreting context, omitting brand-specific terminology, and producing compliant yet useless content. For example, simply labeling a chart as a “color chart” provides no value at all to screen reader users. It is required that AI complete the first round of processing, after which human reviewers audit core content involving clients or legal sensitivities, and accessibility reviews must be embedded into the early stages of the design process.
- [ ] Alt text is reviewed whenever images are added, replaced, or renamed
- [ ] PDFs, Word docs, and slide decks are checked too, not just the website
Frequently Asked Questions
Does alt text really impact SEO rankings?
The answer is yes. It affects rankings indirectly by helping search engines understand the content of images. It must be paired with high-quality content, and cannot be used as a standalone ranking tactic.
What is the ideal length of alt text?
There is no strict upper limit for this metric, but mainstream screen readers will truncate alt text at roughly 125 characters, so you must generate a complete and accurate description within this range.
Should alt text be added to decorative images?
Many developers are confused about whether alt text should be added to decorative images. The correct practice is to retain this attribute but set its value to empty, so that screen readers will skip these images and avoid misinterpreting them.
What is the difference between alt text and image captions?
One might ask: what is the difference between alt text and image captions? Image captions provide supplementary background information for all users, while alt text is only read by screen readers and search engines to describe the content of an image. The two must complement each other, and must not repeat the same content.
Get Your Alt Text — and Your Whole Site — Reviewed
Is it feasible to generate all image alt text entirely using AI?
For websites with a large inventory of stored images, AI serves as a reliable starting point for this work. However, all AI-generated content must undergo human review, with focused verification carried out on product details, data visualizations, and content related to legal compliance.
Alt text, a minor website optimization measure, greatly benefits a website’s inclusivity and discoverability. It is rarely the only accessibility gap on a website; problems with color contrast, keyboard navigation, and form labels often occur in clusters. Our hands-on remediation project addresses the pain point of website operation teams lacking sufficient time and energy to carry out such optimization work.
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