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Alt text and image accessibility glossary

29 terms you meet in audit reports, WCAG documents and WordPress settings, explained in plain words.

This glossary defines the vocabulary around image alt text: what the attribute is, what makes an alt missing, generic or duplicated, how WCAG, the European Accessibility Act and screen readers rely on it, and what it changes for image SEO. Each entry ends with a link to the guide that goes further.

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All terms, A to Z

Click a term to jump to its definition. Below, the terms are grouped by theme: the basics, quality, accessibility and the law, image SEO.

Accessibility overlay Accessibility statement ADA and Section 508 ALT Quality Score Alt tag Alt text Alt text length aria-hidden and role=”presentation” Audit tools: Lighthouse, WAVE, axe Caption Complex image Decorative image Duplicate alt text Empty alt European Accessibility Act Functional image Generic alt text Google Images Image file name Image of text Image SEO Keyword stuffing Missing alt RGAA Screen reader Success criterion 1.1.1 Non-text content Title attribute WCAG WordPress media library

The words attached to every image

The attribute, its empty and missing states, and the fields around it in WordPress.

Alt text

Alt text is the text stored in the alt attribute of an img element. Screen readers read it aloud in place of the image, browsers display it when the file fails to load, and search engines use it to understand what the picture shows.

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Also: alt attribute, alternative text, alt description

A good alt says what the image shows in the context of the page, in a few words or a short sentence. “Woman reading a contract at a kitchen table” works; “image” or “IMG_4832” does not. In WordPress, the alt lives in the media library, in the Alternative Text field of each attachment, and every block that reuses the image picks it up from there.

What is alt text: the full guide

Alt tag

“Alt tag” is the everyday name for the alt attribute. Strictly speaking there is no such tag in HTML: alt is an attribute of the img tag, not a tag of its own.

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Also: image alt tag

The distinction matters when you read documentation or audit reports. When a tool says an image has “no alt tag”, it means the alt attribute is absent from the img element. We write “alt text” on this site and keep “alt tag” for quoting tools that use it.

How to check if an image has alt text

Empty alt

An empty alt is an alt attribute that is present but has no value: alt="". It tells assistive technology to skip the image entirely, which is the right choice for a purely decorative picture.

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Also: alt=””, null alt

The catch is that WordPress writes alt="" for every image whose Alternative Text field was left blank, decorative or not. So an empty alt on a product photo or a chart is a failure, and the same empty alt on a divider line is correct. An audit cannot tell the two apart without a human decision, which is why Filikod lets you mark an image as decorative rather than guessing.

How to find every image missing alt text

Missing alt

An image has a missing alt when the img element carries no alt attribute at all. Unlike an empty alt, nothing tells a screen reader whether the image matters, so most of them read the file name instead.

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Also: missing alt attribute, no alt

This is the message behind “image elements do not have [alt] attributes” in Lighthouse and “the images on this page are missing alt attributes” in SEO checkers. On WordPress it usually comes from a theme or a builder that prints images without the attribute, or from HTML pasted by hand. In our 2,449-image benchmark, 25.2% of images had no usable alt.

The warnings, decoded

Decorative image

A decorative image adds nothing a reader needs to understand the page: a divider, a background texture, an icon next to a label that already says the same thing. The correct alt for it is empty, alt="", so screen readers pass over it.

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The test is one question: if the image disappeared, would a reader lose information? If not, it is decorative. Logos are the usual exception people get wrong. A logo that links to the homepage is functional and needs an alt such as “Filikod, home”. Since version 1.1.0, Filikod has a Decorative switch that excludes an image from the score instead of counting its empty alt as a miss.

Alt text examples, including decorative cases

Title attribute

The title attribute is the text shown in a tooltip when the mouse hovers an image. It is not a substitute for alt: screen readers ignore it by default and touch screens never show it.

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Also: image title, tooltip

WordPress has a Title field for every media file, filled with the file name at upload, and some plugins copy that title into the alt of all images at once. That is how thousands of images end up with an alt like “DSC 0042”. Filikod’s optional “Remove title attribute” setting strips the tooltip from the front end; the alt stays where it is.

How to add alt text in WordPress

Caption

A caption is the visible text printed under an image, in a figcaption element. Everyone sees it, sighted or not, so it should not repeat the alt: the alt describes, the caption comments.

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Also: figcaption, image legend

Example: alt “Line chart of monthly installs from January to August 2026”, caption “Installs doubled after the 1.1.0 release”. If the caption already says everything the image conveys, a short alt or even a decorative one can be defended, but that is a call to make image by image, not a default. WordPress stores the caption in the attachment’s excerpt, separately from the alt.

Alt text examples

Image file name

The file name is the name of the image file on the server, such as red-trail-shoe-side-view.jpg. Search engines read it, screen readers fall back to it when the alt is missing, and several plugins turn it into alt text.

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Also: filename, image slug

A descriptive file name with hyphens helps image SEO and gives generation tools decent material. A camera name like P1040233.JPG does the opposite and, once converted into alt text, produces exactly the generic values Filikod flags. Rename before upload when you can: WordPress does not rename files after the fact without a plugin.

Image SEO for product photos

What separates a filled alt from a good one

The issues Filikod detects and the cases that need a judgement call.

Generic alt text

A generic alt is a value that fills the attribute without describing the image: “image”, “photo”, “logo”, a file name such as IMG_2231, or an AI export name such as “ChatGPT Image Jul 7, 2024”. It passes a presence check and fails a person.

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Also: placeholder alt, filename alt

Generic alts are worse than missing ones in one way: every automated checker turns green while the screen reader user still hears nothing useful. Filikod detects them with a list of patterns in several languages (camera prefixes, placeholders, thumbnail names, AI export names since 1.1.1, single words with digits since 1.1.3) and groups them in a Generic tab.

How the score treats generic alts

Duplicate alt text

A duplicate alt is the same alt text used on two or more different images. It is the typical result of a product import that copies the product name into every gallery photo, or of a bulk tool that writes one sentence everywhere.

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Also: repeated alt, identical alt

For a screen reader user, six images that all say “Speedcross 6 trail shoe” are six times the same nothing. For Google Images, five of the six are noise. In the benchmark, 8% of images carried an alt already used by another image. The fix is to add what each photo shows: the angle, the colour, the detail.

Alt text for WooCommerce galleries

Alt text length

Filikod counts an alt as too short under 8 characters and too long over 125. Below 8 the text cannot describe anything; above 125, older screen readers may cut it off and the description usually belongs in a caption or a paragraph instead.

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Also: too short alt, too long alt, 125 characters

The 125-character figure comes from how JAWS behaved in the early 2010s and has stuck as a working ceiling. It is a guideline, not a WCAG rule: WCAG asks for an equivalent, whatever its length. In practice, most good alts sit between 40 and 100 characters. A too long alt weighs 70/100 in the score, less than a missing or generic one.

The scoring methodology

Keyword stuffing

Keyword stuffing is the habit of packing search terms into the alt, as in “buy cheap trail running shoes online best price trail shoes”. It describes nothing and search engines have treated it as spam for years.

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Also: in alt text

The alt should name what the picture shows. If the product is a trail running shoe, say so once, then say what this photo adds. Google’s own image guidance asks for alt text that is “useful, information-rich” and warns against filling it with keywords. Screen reader users get the same sentence read aloud, which is the fastest way to lose them.

Alt text examples that describe instead of stuffing

ALT Quality Score

The ALT Quality Score is the 0 to 100 number Filikod gives a media library or a page. Each image gets a score from deterministic rules (a missing or generic alt scores low, a too long one 70, a correct one 100), decorative images are excluded, and the score is the average.

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Also: alt score, Filikod score

No AI and no black box: the same image always gets the same score, so the number can be tracked from one month to the next and put in a client report. The benchmark average across 134 audits is 67.6. A library above 90 is clean by any practical standard.

The scoring methodology

Complex image

A complex image carries more information than a sentence can hold: a chart, a map, an infographic, a schema. The alt gives the short version and a longer text nearby gives the data.

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Also: chart, infographic, diagram

For a chart, the alt names the type and the subject (“Bar chart of impressions per week, June to September 2026”) and the paragraph under it, or a table, gives the values. The old longdesc attribute was dropped from HTML5 and most browsers ignore it; use visible text or aria-describedby pointing to it. Infographics pasted as a single JPEG are the case that fails audits most often.

Alt text examples for charts and infographics

Functional image

A functional image triggers an action: a logo that links home, a magnifier icon that opens the search, a thumbnail that opens a product. Its alt describes the action or the destination, not the picture.

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Also: image link, image button

“Search” is the right alt for a magnifier icon button; “magnifying glass icon” is not. When the image sits inside a link with visible text, the image can be decorative and the text carries the meaning. Icon-only buttons without alt are among the most common failures in accessibility audits of WordPress themes.

Alt text examples for links and buttons

Image of text

An image of text is a picture whose main content is words: a quote saved as a PNG, a banner with a slogan, a scanned table. WCAG 1.4.5 asks for real text wherever the design allows it; when the image stays, the alt must contain the same words.

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The alt is straightforward here: repeat the text, in full if it is short. Beyond accessibility, real text can be selected, translated, searched and resized, which an image cannot. Logos are the accepted exception.

WCAG 2.1 for WordPress sites

Who reads alt text, and who requires it

Screen readers, the WCAG criteria and the laws that cite them in Europe, France and the United States.

Screen reader

A screen reader is software that reads a page aloud or sends it to a braille display: NVDA and JAWS on Windows, VoiceOver on Mac and iOS, TalkBack on Android. When it meets an image, it reads the alt; with no alt, it reads the file name or just says “image”.

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Also: assistive technology, NVDA, JAWS, VoiceOver

This is the audience alt text is written for. A screen reader user moves through a page by headings, links and images, so an alt that repeats the heading above it wastes their time, and one that says “image” tells them nothing. Testing with VoiceOver takes five minutes on any Mac and teaches more than any checklist.

What is alt text

WCAG

WCAG are the guidelines published by the W3C for accessible web content. Version 2.1 (2018) is the one most laws cite; 2.2 (2023) adds nine criteria, none of them about images. Each criterion has a level, A, AA or AAA, and the legal target almost everywhere is AA.

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Also: Web Content Accessibility Guidelines, WCAG 2.1, WCAG 2.2, level AA

For images, the criterion that matters is 1.1.1, at level A, the lowest bar. Meeting it means every non-text content has a text alternative that serves the same purpose. There is no separate “WCAG alt text checker”: any tool that finds images without a text alternative is checking 1.1.1.

WCAG 2.1 and the EAA for WordPress sites

Success criterion 1.1.1 Non-text content

Criterion 1.1.1 requires a text alternative for all non-text content, images included, except for decoration (empty alt), CAPTCHAs (describe the purpose) and sensory content such as the sound of an instrument. It sits at level A in every WCAG version since 2.0.

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Also: WCAG 1.1.1

Passing 1.1.1 is a per-image question: is there an alt, and does it serve the same purpose as the image? A generic alt technically has an attribute and still fails, because “image” serves no purpose. Duplicates and file names fail the same way. This is why a presence check is not an accessibility check.

WCAG 2.1 and the EAA for WordPress sites

European Accessibility Act

The European Accessibility Act is EU Directive 2019/882. Since 28 June 2025 it requires certain products and services sold in the EU, including e-commerce sites and online banking, to be accessible, with WCAG 2.1 AA as the technical reference through the EN 301 549 standard.

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Also: EAA, Directive 2019/882

The act applies to private companies, which the earlier public sector directive did not. Micro-enterprises (under 10 staff and 2 million euros of turnover) are exempt from the service obligations; everyone else selling online in the EU is not. Missing alt text on product images is one of the easiest failures to spot and one of the easiest to fix.

What the EAA requires from a WordPress site

ADA and Section 508

In the United States, the ADA is the civil rights law that courts and the Department of Justice apply to websites, and Section 508 is the standard federal agencies must meet. Both point to WCAG 2.0 or 2.1 AA as the measure of an accessible site.

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Also: Americans with Disabilities Act, Title II, Title III

The April 2024 DOJ rule requires state and local government sites to meet WCAG 2.1 AA, with deadlines in 2026 and 2027 depending on population. For private businesses, most of the pressure comes from lawsuits, and “images without alt text” appears in a large share of the complaints because it is trivial to prove with a free scanner.

Accessibility laws and WordPress

RGAA

The RGAA is the French implementation of WCAG for public bodies and for companies above 250 million euros of turnover. Version 4.1 maps every WCAG 2.1 criterion to a set of tests; images are topic 1, and criterion 1.1 asks whether every image carrying information has a text alternative.

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Also: Référentiel général d’amélioration de l’accessibilité

French public sites must publish an accessibility statement with their RGAA compliance rate, and since 2023 the Arcom can fine those who do not. Many French WordPress sites run by local authorities or associations fall under it. If you audit one, the RGAA test wording is what the client will recognise.

Accessibility laws and WordPress

aria-hidden and role=”presentation”

aria-hidden="true" removes an element and everything inside it from the accessibility tree; role="presentation" (or role="none") strips an element of its semantics. On an image, either one tells assistive technology to ignore it, the same effect as an empty alt.

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Also: role=”none”

Use them on decorative inline SVGs, which have no alt attribute, and on icons injected by a theme. Do not put aria-hidden on an image that carries information, and never on a focusable element such as a linked image, or keyboard users land on something that no longer exists for their screen reader. The Filikod checker recognises both attributes as decorative markers.

How to check alt text and decorative markers

Accessibility statement

An accessibility statement is a public page saying which standard the site aims for, how far it complies, what is known to fail and how to reach someone when a page is not usable. The EAA and most public sector laws require one.

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Also: accessibility page, déclaration d’accessibilité

It is also the natural place to be honest about images: “alt text is complete on product pages and being worked on in the blog archive” is a legitimate statement and reads far better than silence. Some sites publish their ALT Quality Score there and update it with each audit.

What the law expects from a WordPress site

Accessibility overlay

An overlay is a script that adds a floating button with contrast, font size and “screen reader” options, sometimes with alt text generated on the fly. Vendors sell it as compliance in one line of code.

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Also: accessibility widget, toolbar plugin

It is not. Overlays do not change the HTML that search engines and real screen readers read, their automatic alts are guesses, and hundreds of accessibility practitioners have signed the Overlay Fact Sheet asking site owners to stop using them. US lawsuits have named sites running overlays. Fix the alt text in the media library instead: with the right list it takes an afternoon.

The Filikod plugin

What alt text changes in search

How search engines use the alt, and the tools that check it.

Image SEO

Image SEO is the set of practices that help search engines understand and rank images: a descriptive alt, a readable file name, text around the image, reasonable dimensions and weight, and structured data where it applies.

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The alt is the signal you control most directly and the one most often left empty. It does not lift a page on its own, but it decides whether a product photo shows up in Google Images, which is a real entry point for clothing, furniture, food and travel. Compression plugins handle weight; none of them writes alt text.

WooCommerce image SEO

Google Images

Google Images is Google’s image search. It indexes pictures from web pages and uses the alt, the file name, the caption and the surrounding text to work out what each one shows, on top of its own image recognition.

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Also: image search

A page can rank in web search and be invisible in image search when its photos have no alt. Search Console reports the two separately (Search type: Image), which is the quickest way to see whether your images bring visits at all. Product and recipe sites usually find a surprise there.

Product images that rank in Google Images

Audit tools: Lighthouse, WAVE, axe

Lighthouse (built into Chrome and PageSpeed Insights), WAVE and axe are the tools that usually raise the alarm: “image elements do not have [alt] attributes”, “missing alternative text”, “images must have alternate text”. They check one page at a time and catch missing attributes, not bad ones.

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Also: accessibility checker, PageSpeed Insights

They are the right first step and a poor last one. None of them can tell that “image” is generic or that six alts are identical, and none of them sees the images in your library that no page shows. The Filikod checker reads one URL with quality rules; the plugin reads the whole media library.

The warnings, decoded

WordPress media library

The media library is where WordPress stores every uploaded file and its metadata. The alt text of an image is the _wp_attachment_image_alt meta of the attachment, edited through the Alternative Text field, and blocks reuse it wherever the image is inserted.

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Also: _wp_attachment_image_alt, Alternative Text field

The library shows no alt column and no filter, so a 500-image site cannot see its missing alts without opening 500 attachments. That gap is the reason Filikod exists: it reads the same meta for every attachment, scores it and lets you edit it from one list. Changing the alt in a block, on the other hand, only changes that block.

Bulk edit alt text in WordPress

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