When people talk about image SEO, they almost always talk about alt text. Alt text matters, and we have a full guide on writing alt text for SEO and accessibility. But many business owners believe that alt text is the only way Google understands an image. It isn’t.
Google reads the whole page around an image: the caption under it, the paragraph next to it, the heading above it and the topic of the page itself. On most sites, that surrounding text is left to chance. Images get dropped wherever they fit the design, captions are missing or say “Image 1,” and the paragraph that explains the picture sits three scrolls away.
In this guide, let me explain how Google uses captions and nearby text, how captions differ from alt text and titles, how to write captions people actually read, how to mark them up properly, and how to handle charts and data images. I will finish with some before-and-after examples you can copy.
How Google works out what an image shows
Search engines have become better at recognizing what is inside a picture, but Google’s own guidance still points to words on the page. Its image guidelines say so directly:
“Google extracts information about the subject matter of the image from the content of the page”
— Google Search Central, Google image SEO best practices
The same guidance names captions and image titles among those sources. The SEO Starter Guide adds a simple line that sums up the whole idea: “The text that’s near images can help Google better understand what the image is about” (Google SEO Starter Guide).
So in practice, Google can draw on several layers of text when it looks at an image:
- The file name, such as
gutter-guard-before-after.jpg. - The alt text inside the
<img>tag. - The caption directly under or above the image.
- The nearby paragraph and heading that discuss the same thing.
- The page title and topic as a whole.
When all five layers agree, the image is easy to understand. When they disagree, for example a photo of a kitchen on a page about roof repair with a caption that says “Our team,” the signal is muddy. If you are new to image basics, our lesson on image SEO: alt text, file names and speed covers the first two layers. This article is about the rest.
Caption, alt text, title attribute and nearby copy: four different jobs
These four are often mixed up, so let me put them side by side.
| Element | Who sees it | Main job | Typical length |
|---|---|---|---|
| Alt text | Screen reader users; everyone if the image fails to load; search engines | Replace the image with words when it can’t be seen | A short phrase or sentence |
| Caption | Every visitor; search engines | Add context the image can’t give on its own | One or two sentences |
| Title attribute | Mouse users who hover; not reliably read by screen readers | Optional extra tooltip | A few words, if used at all |
| Nearby copy | Every visitor; search engines | Explain the point the image supports | A paragraph or more |
The most useful rule I can give you: alt text says what the image shows; the caption says why it matters. WebAIM’s guidance on alt text makes a related point: when an image has a caption, the alt text should not simply repeat it (WebAIM). Ahrefs’ alt text guide says much the same thing: if a caption already describes the image, repeating it in the alt text is redundant.
The title attribute is the weakest of the four for people. I rarely add one. If you want the details on that, read our article on the title attribute and SEO.
What a useful caption says that the image cannot
A photo can show you a cracked foundation. It can’t tell you where it is, how old the crack is, what caused it, or what the repair cost. That is the caption’s job. Good captions usually add one or more of these:
- What to notice. “Note the hairline crack running from the window corner.”
- Context. Where, when, which product, which model or version.
- Numbers. Sizes, results, dates or prices that the picture alone can’t show.
- Source or credit. Who took the photo, or where the data came from.
- The takeaway. The one point you want the reader to remember from the image.
And here is what bad captions look like:
- “Image 1” or “Photo” (no information at all).
- A copy of the alt text, word for word.
- A string of keywords: “roof repair roofing contractor roof leak fix Dallas.”
- A caption that doesn’t match the image, often left over from an old template.
A caption pattern for each common image type
Different images need different captions. Here is the pattern I suggest for the image types most business sites use.
| Image type | Caption pattern | Example |
|---|---|---|
| Before-and-after photo | What changed + timeframe | “The same patio before and after pressure washing, taken two hours apart.” |
| Product detail | Feature + why it matters | “The double-stitched heel seam, which is where most hiking boots fail first.” |
| Software screenshot | Where in the tool + what to click or notice | “Search Console’s Performance report with Search type set to Image.” |
| Chart or graph | Main finding + data source and date | “Organic leads grew every month from January to June (example data).” |
| Process step | Step number + action | “Step 3: seal the joint with butyl tape before fitting the flashing.” |
| Team or location photo | Who, where, doing what | “Our installation crew fitting solar panels on a farmhouse roof.” |
Marking up captions with figure and figcaption
Visually, a caption is just small text under an image. In HTML, it is better to tie the two together with the <figure> and <figcaption> elements. That makes the relationship clear to browsers, assistive technology and any system reading your page’s structure. MDN describes the accessibility benefit directly:
“The <figcaption> provides the accessible name for the parent <figure>.”
— MDN Web Docs, The figure element
Here is a basic example you can copy:
<figure>
<img src="/images/gutter-guard-before-after.jpg"
alt="Gutter half full of wet leaves next to a clean gutter fitted with a mesh guard"
width="1200" height="800">
<figcaption>Same roof, one autumn apart: the left run has no guard, the right run has a fine stainless mesh guard.</figcaption>
</figure>A few rules that keep this markup clean:
- One figcaption per figure. It can be the first or last child of the
<figure>. - Keep alt text on the img. A caption does not replace the alt attribute. Write alt text that describes the image, and a caption that adds context.
- Don’t use figure for every image. It is meant for self-contained content that is referenced by the main text, such as a photo, diagram, chart or code example. Decorative images and icons don’t need it.
- Make the caption real text. Don’t bake captions into the image file. Text inside an image is harder to read, can’t be translated and isn’t easy for search engines to use.
- Check what your CMS outputs. In WordPress, the Image block wraps an image in a figure and puts its caption in a figcaption. Some page builders use plain
divelements instead. View the page source to check.
A note on sitemaps: Google used to accept an <image:caption> tag in image sitemaps, but that tag was deprecated in 2022, and Google’s image sitemap documentation now lists it as removed. Captions belong on the page. Our guide on image sitemaps explains what still belongs in the sitemap.
Placing images next to the words that explain them
Placement is the most overlooked part of this. Google’s guidance is short and practical:
“Wherever possible, make sure images are placed near relevant text and on pages that are relevant to the image subject matter.”
— Google Search Central, Google image SEO best practices
In real pages, here is what that means:
- Put the image inside the section it supports, right after the paragraph that introduces it. Not at the top of the article as a generic header, and not in a gallery at the bottom.
- Refer to the image in the text. A line like “As the photo below shows, the crack runs from the window corner” links your words to the picture.
- Keep one topic per section. If a section covers two products, place each product’s image next to its own paragraph.
- Use a descriptive heading above the section. The heading is part of the context too.
- Avoid sliders for important images. Carousels often push images away from the text that explains them, and later slides may only load on click.
Here are the placement problems I see most often, and the simple fix for each:
| Placement problem | Why it weakens the signal | Fix |
|---|---|---|
| Generic hero image at the top of every post | The image has no clear link to any one paragraph | Use a topic-specific image, or move the explanatory image into the section it supports |
| All photos collected in a gallery at the end | Each photo is far away from the text that describes it | Spread the photos through the article, one per relevant section |
| Image in a sidebar widget | The sidebar text is usually unrelated to the image | Move important images into the main content |
| Text baked into the image | The words can’t be read as page text | Put the words in a caption or paragraph; keep the image clean |
| Same stock photo used on many pages | The image says nothing specific about any page | Use an original image instead of a stock photo |
This also matters for people coming from Google Images. When someone clicks an image result, they land on your page and look for the image. If it sits next to a clear explanation, they stay. Our guide on getting traffic from Google Images covers that visitor’s journey in more depth.
Captions for charts, graphs and data images
Charts are where captions do the most work. A chart is packed with information, and alt text alone can’t carry it. The W3C’s accessibility tutorial puts it this way:
“Complex images contain substantial information – more than can be conveyed in a short phrase or sentence.”
— W3C Web Accessibility Initiative, Complex images tutorial
The W3C suggests a two-part approach: a short text alternative that identifies the image, plus a longer description that gives the key information in text. A <figure> with a <figcaption> is one of the approaches it describes, and it has a nice side effect: the full description is visible to every reader and to search engines.
Here is how I would caption a chart, step by step:
- Start with a short title in bold: what the chart measures and the time period.
- State the main finding in one plain sentence. Most readers only want this.
- Give the key numbers in text, so they can be read, copied and quoted.
- Name the source and date of the data. If the data is illustrative, say so.
- Keep the alt text short and point to the caption, or give a one-line summary.
- For big data sets, add a table below the chart with the full numbers.
<figure role="group" aria-labelledby="fig3-cap">
<img src="/images/lead-sources-2026.png"
alt="Bar chart of leads by source; details in the caption">
<figcaption id="fig3-cap">
<strong>Leads by source, Jan–Jun (example data).</strong>
Organic search brought 410 leads, paid search 260, referrals 90 and social 40.
Organic search was the largest source in every month.
</figcaption>
</figure>That example uses made-up numbers for illustration, which is why the caption says “example data.” Do the same on your own site whenever a chart is not based on real data. For more on making charts readable, see our guide to data visualization in content.
Three caption rewrites, before and after
Let me show you what this looks like on real-world kinds of pages. These are examples I wrote for this article, not client pages.
A plumber’s blog post about water heaters
Before: no caption. Alt text: “water heater.”
After: Alt text: “Corroded bottom of a tank water heater with rust stains on the floor.” Caption: “Rust around the base of the tank usually means the tank itself is leaking, which can’t be repaired; it needs replacing.”
The alt text describes the picture. The caption adds the expert point a homeowner needs.
A software company’s how-to guide
Before: Caption: “Screenshot.” Alt text: “screenshot.”
After: Alt text: “Export settings dialog with CSV format selected.” Caption: “Choose CSV, not XLSX, if you plan to import the file into another tool. CSV is the format most import tools accept.”
An online store’s product page
Before: Caption: “Best waterproof hiking boots cheap hiking boots men.”
After: Alt text: “Hiking boot sole with deep, multi-directional lugs.” Caption: “5mm lugs grip wet rock and mud; the sole is replaceable by any cobbler.”
For store images specifically, our guide to product image alt text goes deeper into the alt side.
How captions, alt text and AI tools fit together
Many sites now use AI tools to write alt text in bulk. That can save time, but these tools only see the image. They don’t know why it is on the page. A caption written by someone who knows the topic adds exactly what the AI can’t: the reason the image matters. If you use AI for alt text, read our guide to AI-generated alt text first, and keep captions written by a person on your most important images.
Captions also matter for images that should not get alt text at all. When a caption next to an image fully explains it, the image may be redundant for screen reader users, and empty alt text can be the right choice. The W3C’s informative images tutorial makes a similar point about images whose content is already described in nearby text. I cover that edge case in our guide to decorative images and empty alt text.
Questions about image captions and SEO
Do image captions help SEO?
Google says it uses page content, including captions, to understand what an image is about. So a clear caption gives Google more context for the image and helps readers at the same time. It is a supporting signal, not a ranking shortcut.
Should my caption and alt text say the same thing?
No. Screen reader users hear both, so repeating the same words is tiresome. Let the alt text describe what the image shows, and let the caption add context: why it matters, where it came from, or what to notice.
Does every image need a caption?
No. Captions earn their place on charts, screenshots, process photos, product details and anything a reader might misread. Decorative images, logos and simple illustrations usually don’t need one.
Does Google read the image title attribute?
Google’s image guidelines mention captions and image titles as sources of information, but the title attribute is weak for people: it only shows on mouse hover and is not reliably read by screen readers. Put important information in visible text instead.
Can I still put captions in my image sitemap?
No. Google deprecated the image:caption sitemap tag in 2022. Captions now need to be on the page, ideally in a figcaption element next to the image.
Where to start with your image captions this week
You don’t need to caption every image on your site. Start where captions add the most:
- Your top 10 pages by traffic: check every chart, screenshot and product photo.
- Any image that sits far away from the text that explains it: move it.
- Captions that repeat alt text or contain keyword lists: rewrite them.
- Your theme or page builder: confirm it outputs figure and figcaption.
For the full image picture, from file sizes to formats, read our guide to image SEO. And if you want help writing clear, useful copy around your images, our content writing service can take it off your plate. Just get a free quote and tell us about your site.
Further reading on image captions seo
- Decorative Images: When to Leave Alt Text Empty
- Internal Anchor Text Audit: Fixing Over-Optimized Links
- Original Images vs Stock Photos: Does It Matter for SEO?
