Image SEO Checklist for Contractors

The short version: image SEO is the practice of making your website's images understandable to search engines and fast enough not to hurt your rankings. For contractors, whose websites are mostly photographs of completed work, SEO image optimization matters more than for almost any other business type — and it's usually the most neglected part of the site.

This is the technical checklist. Work through it in order.

Why image SEO matters for contractor websites

A contractor's website is a portfolio. Pools, kitchens, decks, outdoor living spaces — the visual content is the content. Search engines can see a photograph, but only partly. Google says it combines alt text, computer vision and the page's content to understand one. Most signals sit around it: the file name, the alt attribute, the relevant text nearby, the schema markup, and how fast it loads.

Get those wrong and two things happen. Your images never surface in Google Image search, which is a meaningful discovery channel for visual categories. And your pages load slowly, which affects user experience and, through Core Web Vitals, your search performance.

Get them right and every project photo becomes another entry point for organic growth.

Google Images and image search

Google Image Search is a genuine traffic source for visual businesses, and it behaves differently from text SEO. Google matches an image to search queries using what it can infer about the subject. Much of that inference comes from text you control.

The signals that decide whether your website's images appear:

The file name and the src attribute path
The alternative text
The descriptive text surrounding the image on the page
The page's own title and topical relevance
Structured data referencing the image

An image with a generic file name, no alt tag, and no relevant information around it is effectively invisible to image search, no matter how good the photograph is.

Image file names

Rename every file before uploading. Camera output like IMG_4471.jpg or DSC00118.JPG tells search engines nothing about what the image depicts.

Rules:

Hyphens between words, not underscores or spaces
Short but descriptive, which is Google's own advice
Describe what's actually in the image, not what you wish to rank for
Lowercase throughout, for consistent image URLs

This is the cheapest win on the list. It costs nothing and almost nobody does it.

Descriptive alt text

The alt attribute is a written description of the image. It serves two purposes: screen readers announce it to visually impaired users, and Google calls it the most important attribute for image metadata.

html

How to write alternative text:

Describe the image accurately and naturally
Keep it to a sentence: describe the image, not the whole page
Include relevant keywords only where they genuinely describe what's shown
Skip "image of" or "photo of" — redundant
Avoid keyword stuffing. An alt tag reading "pool builder Dallas pool contractor Frisco pool company Plano" helps nobody and degrades accessibility. Google warns it may also get a site seen as spam

Functional images — a logo that links home, an icon that acts as a button — need alt text describing the function, not the appearance. A phone icon linking to your number should read "Call Carpenter Growth," not "phone icon."

Decorative images — dividers, background textures, an icon repeating adjacent label text — take an empty alt attribute (alt=""), which tells assistive technology to skip them. Not every image needs a description.

Missing alt text leaves both screen readers and search engines without context. Run a site crawl to find them.

Alt attribute vs title attribute

These are not the same and the title attribute is not a substitute. alt is the accessible description search engines read. title produces a tooltip on hover, isn't reliably announced by screen readers, and carries little SEO weight. Fill in alt. Leave title alone unless you have a specific reason.

Image formats

Format affects file size, quality, and loading speed.

Google supports BMP, GIF, JPEG, PNG, WebP, SVG, and AVIF for indexing. Practically, you'll use four:

WebP — the recommended default for general images. 25–34% smaller than JPEG at equivalent quality (Google's figure for lossy WebP), supports background transparency, universally supported in current browsers.

AVIF — smaller still, with slightly less universal support. Good with a WebP fallback.

PNG — your site logo, sharp-edged graphics, anything needing transparency. Poor for photographs; file sizes balloon.

SVG — logos and icons only. Scales to any resolution without quality loss.

For a contractor site: photographs as WebP, logo as SVG or PNG.

Image quality and resizing images

High quality images sell the work. Oversized files destroy loading speeds. Both are true.

Resize images before uploading. Serving a 6000-pixel camera file and letting the browser scale it down means every visitor downloads the full original for no benefit.

Practical dimensions:

Hero images: 1920–2500 pixels wide
Gallery and project images: 1200–1600 pixels wide
Thumbnails: 400–600 pixels wide

For Google Discover, Google recommends large images at least 1200 pixels wide.

Use original photography, not stock photos. Stock images appear on thousands of sites, carry no unique signal, and for a contractor they actively undercut the pitch. A prospect who reverse-image-searches your "portfolio" and finds it on a stock library has learned something. Original project photos are the only visual content that differentiates you.

File size and compression

Compressing images reduces file size so pages load faster.

Lossy compression removes non-essential data — file size drops substantially, quality drops slightly. For web photographs, well-tuned lossy compression is invisible.

Lossless compression retains full quality but saves less space. Use for logos and graphics where artifacts would show.

Tools: TinyPNG, Squoosh, ImageOptim, or automatic compression in your CMS.

Target file sizes:

Hero image: under 300 KB
Gallery image: under 150 KB
Thumbnail: under 50 KB

Use a CDN. A Content Delivery Network serves your site's images from a server geographically near the visitor, cutting latency and speeding up faster loading noticeably on image-heavy pages. Most modern hosts include one; Cloudflare's free tier covers it if yours doesn't.

Responsive images

Responsive image scaling serves different versions to different screen sizes, so a phone doesn't download a desktop-sized file. Many users reach contractor sites on mobile, which makes this essential rather than optional.

The srcset attribute specifies different image versions for different screen resolutions:

html

For more control — serving a different crop on mobile, or offering AVIF with a WebP fallback — the <picture> element groups multiple <source> versions:

html

Most site builders generate responsive images automatically — WordPress has included srcset support by default since version 4.4. Check that yours actually is, rather than assuming. If you're unsure, this is a reasonable thing to ask a web developer to verify.

Lazy loading

Lazy loading defers image loading until needed, improving initial load time on image-heavy pages — exactly the situation on a project gallery.

html

One critical exception: never lazy-load your hero or anything above the fold. That's usually your Largest Contentful Paint element, and lazy-loading it hurts the metric you're trying to improve.

Core Web Vitals and images

Images affect two of the three Core Web Vitals directly.

Largest Contentful Paint (LCP) is usually an image on a portfolio site. Compress it, serve a modern format, don't lazy-load it, and consider fetchpriority="high" on the hero.

Cumulative Layout Shift (CLS) happens when images load without reserved space and shove content around. Always specify width and height on every img tag so the browser reserves the space before the image arrives.

Small fix, outsized effect, missing on most contractor sites.

Image sitemaps

An image sitemap helps search engines crawl and index images they might otherwise miss — particularly images loaded with JavaScript.

Google accepts image entries in your existing sitemap, next to each page entry:

xml

Useful detail: image sitemaps can list images on other domains, such as a CDN. Google's condition is that you verify both domains in Search Console. Bing reads image sitemaps for indexing as well.

If your CMS generates sitemaps automatically, check whether images are included. Many don't by default.

Schema markup for images

Structured data helps Google understand what's on the page, and it can make a page eligible for rich results.

Reference images inside the relevant schema type — ImageObject where appropriate, and image properties within Article, Product, or LocalBusiness markup. For contractors, project pages are the natural home for this.

Validate with Google's Rich Results Test before assuming it works.

Open Graph and Twitter card tags

These control how your page renders when shared on social platforms and in messaging apps.

html

Facebook recommends at least 1200 × 630 pixels. Without these, a shared link renders blank — a wasted impression every time someone forwards your project page to a spouse or neighbor.

Set a unique og:image on every important page, not just the homepage.

Surrounding text and captions

Google uses captions and text near an image to understand its subject. A product image or project photo sitting alone in a gallery grid has almost no context. The same photograph on a project page, with a caption and descriptive text about the job, has plenty.

Image captions are read by users and search engines alike, and tend to get read more than body copy. Use them on project photos to state what's shown and where.

This is the strongest argument for breaking one gallery page into individual project pages: it gives every image real surrounding context instead of none. Planning those pages is part of my SEO content strategy work.

Images and AI search

Discovery is increasingly happening through AI Overviews and AI assistants that surface and cite visual content. The signals that make an image comprehensible to those systems are the same ones on this list — descriptive file names, accurate alternative text, schema markup, and meaningful text around the image.

Nobody should rebuild a strategy around AI search yet. But sites that already do image optimization properly are positioned for it by default, and sites that don't are accumulating a gap.

Verifying your work

Google Search Console — the URL Inspection tool shows how Google renders a page and which resources loaded. Confirm your images are being fetched.

PageSpeed Insights — flags oversized images, missing dimensions, and images not served in modern formats.

A site crawl — Screaming Frog or similar lists every image with missing alt text, oversized file size, and broken image URLs.

Track image search impressions on their own: in Search Console's Performance report, set the search type to Image. That tells you whether any of this is producing more traffic.

The complete checklist

One thing the checklist can't fix

All of the above makes your images findable and fast. None of it makes them good.

A perfectly optimized photograph taken at noon from chest height with a garden hose in frame is still a photograph that costs you the job. High-quality images contribute to engagement and to whether a visitor becomes a qualified lead — and for contractors, image quality is a conversion problem before it's a technical one. No plugin handles that part.

I wrote about that side separately: what bad photography costs you in search. For builders, SEO for home builders shows how photos and project pages fit together.

Carpenter Growth handles both halves for high-ticket home service businesses in Dallas-Fort Worth — the technical optimization and the photography itself. Start a conversation.

This note is part of the broader Contractor SEO: The Complete Guide.

To see how those optimized images belong inside a broader contractor site, read Contractor Website Structure: What Every Page Needs.