Image Alt Text SEO: 7 Proven Tips to Boost Rankings and Clicks

Quick Answer: Image alt text is a short text description added to an HTML image tag that tells search engines and screen readers what an image shows. For SEO, alt text is one of eight keyword placement zones on a webpage. Write it to accurately describe the image, include your keyword where it fits naturally, stay under 125 characters, and never leave it blank. Every image on every page of your site should have a unique, descriptive alt attribute.

Why Alt Text Is the Placement Zone Nobody Uses

If you audited every image on your website right now, what would you find?

If your site is typical, most images have blank alt attributes. Some have file names like “IMG_3847.jpg” accidentally used as alt text. A few have generic descriptions like “team photo” or “product image.” And a handful, if you hired an SEO agency at some point, might have keyword-stuffed descriptions that sound nothing like natural language.

This is the state of image alt text on most websites, and it represents one of the clearest competitive advantages available to anyone who takes twenty minutes to fix it.

Every image on your page is an opportunity. An opportunity to reinforce the topical relevance of the page, to appear in Google Images searches, to serve visually impaired users who rely on screen readers, and to signal to Google’s language systems that you understand your subject in sufficient depth to describe its visual dimension accurately.

Most of your competitors are leaving all of those opportunities blank. Literally blank.

This guide covers exactly what to write and where to put it.

What Alt Text Actually Is (And What It Is Not)

The Technical Definition

Alt text is the text inside the alt attribute of an HTML image tag. In raw HTML it looks like this:

<img src="keyword-placement-diagram.png" alt="Diagram showing the eight keyword placement zones on a webpage for on-page SEO">

The alt attribute was originally designed for one purpose: to provide a text alternative when an image cannot be displayed. Early internet connections were slow. Images often failed to load. The alt text appeared in the broken image box so users understood what they were missing.

That original purpose still applies, but two more have been added in the decades since.

Screen reader software reads alt text aloud to visually impaired users, making it the primary way blind and low-vision users understand image content. This makes alt text an accessibility requirement, not a suggestion, under WCAG 2.1 accessibility standards that apply to most commercial websites.

Search engines read alt text as contextual information about image content and about the page those images appear on. Google cannot “see” images the way humans can. Its image understanding has improved dramatically with machine learning, but alt text remains one of the clearest signals available for telling Google what an image shows and how it relates to the surrounding content.

What Alt Text Is Not

It is not a keyword field. Writing alt="seo keywords website add keywords seo keyword placement seo" is keyword stuffing applied to an image. Google penalizes it. Screen readers announce it. Both outcomes are bad.

It is not a caption. Captions appear visibly beneath an image and are read by all users. Alt text is invisible in normal browsing and appears only in specific circumstances (broken image, screen reader, source code inspection). They serve different purposes and should be written differently.

It is not a file name. Uploading an image and leaving its file name as the alt text is a CMS behavior some platforms exhibit automatically. A file name like “shutterstock_1234567.jpg” or “IMG_20240312_153422.png” provides no useful information to anyone.

How Alt Text Affects SEO Rankings

Alt text influences search performance through three distinct mechanisms.

Mechanism 1: On-Page Keyword Relevance

Alt text is one of eight keyword placement zones on a webpage, as covered in the complete guide to adding keywords to a website for SEO. When your page has multiple placement signals all pointing to the same keyword, the cumulative relevance signal is stronger than any single placement alone.

A page with the keyword in the title, H1, URL, first paragraph, two subheadings, and body copy already has a strong relevance signal. Adding keyword-relevant alt text to images that appear on that page strengthens the signal further without requiring additional body copy.

Mechanism 2: Google Images Traffic

Google Images is a significant and widely underestimated traffic source. Users searching for diagrams, how-to visuals, product photos, infographics, and reference images often find and click through to source pages from image results.

For your images to appear in Google Images searches, Google needs to understand what each image shows. Alt text is one of the primary inputs for that understanding. An image with accurate, keyword-relevant alt text is indexable as a relevant result for image searches that match its description. The same image with a blank alt attribute is invisible to image search.

Mechanism 3: Accessibility as an Indirect Ranking Signal

Google has stated that page experience signals influence rankings. Accessibility is increasingly considered a component of page experience. While Google has not explicitly stated that alt text failures directly reduce rankings, the relationship between accessibility compliance and page quality scores is directional.

More concretely: Google uses machine learning models trained on human quality assessments. Human quality raters are instructed to evaluate page accessibility and usability. A page with dozens of images and zero alt text fails basic accessibility standards in ways that quality raters notice and penalize.

4-Step Guide to Image Alt Text SEO That Boosts Rankings and Traffic

The standard that satisfies accessibility requirements, performs well in image search, and contributes to on-page keyword relevance is the same standard. You do not need to choose between writing for users and writing for search engines. The optimal alt text does both simultaneously.

Follow these four principles.

Principle 1: Describe What Is Actually in the Image

Alt text is a description, not an interpretation. It tells a user who cannot see the image what the image shows. Start by asking yourself: if I described this image to someone on a phone call, what would I say in one sentence?

For a screenshot of the Yoast SEO keyword field in WordPress: “Screenshot of the Yoast SEO focus keyphrase field in the WordPress post editor with the keyword how to add keywords entered.”

For a diagram showing bounce rate concepts: “Bar chart showing bounce rate percentages for blog pages, product pages, and landing pages with the blog pages column highlighted.”

For a photo of someone using a laptop at a desk: “Person typing on a laptop at a wooden desk with an open notebook and coffee mug beside them.”

Each description tells an unsighted user exactly what is in the image. Each one is also useful to a search engine trying to understand the image’s content and context.

Principle 2: Include Your Keyword Where It Fits Naturally

Your keyword should appear in your alt text when the image actually depicts something related to your keyword. This is the important qualifier: the keyword must fit the description, not be inserted into it.

For a page targeting “how to add keywords to a website” with an image showing keyword placement zones:

Natural: “Infographic showing the eight keyword placement zones on a webpage including the title tag, H1, URL, and meta description.”

Forced: “How to add keywords to a website showing where to add keywords on a website for SEO keyword placement.”

The natural version includes the core concepts without reading like a machine wrote it. The forced version is keyword stuffing with alt text formatting.

When your image does not naturally relate to your target keyword, do not force the keyword in. Write an accurate description and leave the keyword out. An alt text without the keyword is far better than an alt text that reads as manufactured.

Principle 3: Stay Under 125 Characters

Most screen readers stop reading alt text at approximately 125 characters. Longer descriptions get cut off for the users who rely on them most. Write concisely. If an image requires more than 125 characters to describe accurately, consider whether the description belongs in a caption or in the surrounding body text instead.

Principle 4: Make Every Alt Text Unique

Duplicate alt text across multiple images on the same page, or across different pages of your site, is a missed opportunity and a mild accessibility violation. Each image is different. Each alt text should be different. There are no acceptable shortcuts here.

Alt Text for Different Image Types

Different image categories require different alt text approaches.

Informational Images

These are images that add meaning to the surrounding content: diagrams, charts, screenshots, infographics, instructional visuals. Write descriptive alt text that conveys the information the image communicates.

For a chart: Describe the type of chart, what it is measuring, and the key data point or trend. “Line chart showing organic search traffic growth from 0 to 45,000 monthly visitors over 18 months after implementing an on-page SEO strategy.”

For a screenshot: Describe what is shown in the interface, not what the page is about. “Google Search Console Performance report showing the Queries tab with impressions, clicks, and average position columns visible.”

Decorative Images

Purely decorative images (background textures, dividers, abstract shapes used for visual design) do not convey meaningful content and should have empty alt attributes, written as alt="". This tells screen readers to skip the image rather than announcing something irrelevant to the user.

The empty alt attribute is correct. The absent alt attribute is incorrect. One tells the screen reader there is nothing meaningful to announce. The other leaves the screen reader to announce the file name instead.

Product Images

For eCommerce pages, product images are among the most SEO-critical images on the site. Write alt text that includes the product name, key differentiating attributes, and any relevant category terms.

“Nomad slim leather card wallet in full-grain brown leather, open showing eight card slots and a cash pocket.”

That description is accurate, contains the product name, describes the attributes a buyer cares about, and would help Google index the image appropriately for relevant product searches.

Images of People

When an image shows a named person in a context where their identity is relevant (a headshot on an about page, a photo of a speaker at an event), include their name.

“Portrait photograph of marketing consultant Ajit Kumar Gupta in a navy blazer against a white background.”

When the people in an image are anonymous (stock photos, illustrative images of users), describe their role or action without fabricating identities.

“Small business owner reviewing website analytics on a laptop in a coffee shop.”

Common Alt Text Mistakes That Hurt Rankings and Accessibility

Leaving Alt Text Blank

The most common mistake by a wide margin. Blank alt attributes fail accessibility users, provide no signal to search engines, and leave Google Images traffic entirely uncollected. If the image is decorative, use alt="". If it is informational, write a description. Never leave the attribute absent.

Keyword Stuffing in Alt Text

alt="seo keywords website how to add keywords seo keyword placement google seo"

Google’s spam detection applies to alt text the same way it applies to body content. Unnatural repetition of keywords in alt attributes is a signal of manipulation, not relevance. It can trigger manual or algorithmic penalties. More importantly, it provides a poor experience for screen reader users who hear that text read aloud.

Using the Filename as Alt Text

Some CMS platforms auto-populate alt text with the image filename when none is provided. If your filename is “shutterstock_129384756_editorial_use_only.jpg,” that is what screen readers announce and what Google reads. Always override the auto-populated alt text with an actual description.

Writing “Image of…” or “Photo of…”

Screen readers already announce when they encounter an image, so beginning your alt text with “image of” or “photo of” is redundant. Start directly with the description. Not “Image of a diagram showing keyword placement,” but “Diagram showing keyword placement zones on a webpage.”

Identical Alt Text Across Multiple Images

On product pages especially, it is common to see five product images all labeled with identical alt text. Each image shows something slightly different (front view, side view, detail shot, lifestyle context). Each alt text should reflect that difference specifically.

How to Add Alt Text on Every Major Platform

WordPress (Gutenberg Editor)

Click any image block in the editor. In the right sidebar under “Block,” find the “Alt text (alternative text)” field. Write your description directly into this field. Alternatively, click “Open Media” on any image in the media library and find the alt text field in the attachment details panel on the right side.

WordPress (Classic Editor)

Click any image in the content area. Click the pencil (edit) icon. An image details popup opens. The “Alternative Text” field is where alt text lives in the classic editor.

Wix

In the Wix Editor, double-click any image to open its settings. Find the “What’s in the image? It’s good for SEO” field (Wix labels it as the accessibility description). Enter your alt text and click Apply.

Squarespace

Click any image block in the Squarespace editor. In the settings panel that appears, look for the “Alt text” or “Image description” field. Some Squarespace versions require clicking the accessibility tab within image settings.

Shopify

In the Shopify admin, open the product page. Below each product image, there is a small alt text field. Click it to edit. For images uploaded to Files or used as collection images, open the image and find the alt text field in its settings panel.

Using a WordPress SEO Plugin

Yoast SEO and RankMath both flag missing alt text in their page analysis panels. Yoast’s SEO analysis section will show a red or orange bullet if images on your page are missing alt text, with a link directly to the image settings. Use this as an audit tool if you are uncertain which images on a given page need attention.

How to Audit and Fix Alt Text on Your Existing Website

If your website has been live for more than a year and you have never systematically written alt text, you likely have hundreds or thousands of images with blank or inadequate descriptions. Here is how to audit and fix them efficiently.

Step 1: Find the Scale of the Problem

Use Google Search Console’s accessibility or coverage reports as a starting point, then run your site through a dedicated accessibility checker. Free tools like WebAIM’s WAVE or Google’s Lighthouse (built into Chrome DevTools) will identify images with missing alt text on any given page.

For a full site audit, tools like Screaming Frog SEO Spider can crawl your entire site and export a list of every image URL along with its current alt text (or the absence of one). Filter the export for blank alt attributes and you have your complete fix list.

Step 2: Prioritize High-Traffic Pages First

Do not try to fix every image on your entire site in one session. Pull your top 20 pages by organic traffic from Google Search Console. Fix the images on those pages first. The pages already receiving traffic will benefit most immediately from improved image relevance signals.

Step 3: Work Through the Fix List Systematically

For each image on your priority pages, write alt text following the four principles outlined earlier: accurate description, keyword where natural, under 125 characters, unique per image. Open the page in your CMS, find each image, and add the alt text in the platform-specific location described in the previous section.

Step 4: Address Existing Keyword-Stuffed Alt Text

If a previous SEO effort resulted in keyword-stuffed alt text across your images, replacing those with natural descriptions is as important as filling in blank ones. Keyword-stuffed alt text is an active negative signal. Natural descriptions are a positive one.

How Alt Text Fits Into Your Full On-Page Strategy

Alt text does not operate in isolation. It is one element within a complete on-page optimization framework, and its impact is compounded when combined with the other elements.

The guide to where to put keywords on a page covers all eight keyword placement zones in priority order, with alt text placed in zone seven. Understanding how alt text fits within the hierarchy of placement zones prevents over-optimizing images at the expense of higher-priority elements like the title tag and H1.

The on-page SEO checklist includes image alt text as one of its required checkpoints. Use it as a pre-publish verification that no image on any new page you publish goes live with a blank alt attribute.

Every image on a well-optimized page should contribute to the page’s relevance signal. When every placement zone fires correctly, the cumulative effect is a page that scores well across the full spectrum of signals Google uses to evaluate topical authority.

Frequently Asked Questions

Key Takeaways

Alt text is not optional and it is not a technicality. It is a keyword placement zone, an accessibility requirement, and a Google Images traffic mechanism all wrapped into a single HTML attribute.

Write alt text that accurately describes the image, includes the keyword where it fits naturally, stays under 125 characters, and is unique for every image on every page. Use alt="" for genuinely decorative images rather than leaving the attribute absent.

Audit your existing site with a free crawler, prioritize high-traffic pages, and work through the fix list systematically. Every blank alt attribute you fill in is a competitive advantage over every competitor who did not bother.