Images are not just visual decoration — they are a significant ranking factor, a Core Web Vitals driver, and a standalone search channel that delivers measurable organic traffic. Google Images delivers 22.6% of all web traffic, and Google Lens processes over 12 billion visual queries per month. Despite this, image optimization remains one of the most overlooked areas of technical SEO.
Research shows that images are featured on 37.81% of SERPs. Businesses that ignore image SEO are leaving a substantial share of that visibility on the table.
This guide covers the five most impactful ways to optimize images for SEO, grounded entirely in current Google guidelines, Core Web Vitals research, and industry data — not guesswork.
Table of Contents
Why Image SEO Matters for Organic Rankings
Since images typically comprise 50 to 90 percent of page weight, optimization delivers the most significant performance gains. Proper image optimization can dramatically improve loading speed, often reducing page load times by 50 to 70 percent for image-heavy pages.
Images contribute significantly to a website’s page weight, with desktop images averaging over 1,000 KB out of a total of 2,315 KB — that is nearly 50%. On mobile, images account for almost 900 KB out of 2,020 KB.
The number one search result receives 27.6% of all clicks and is 10 times more likely to receive a click compared to the 10th spot. Only 0.63% of users click anything on the second page of results. Page speed — which image optimization directly influences — is a confirmed Google ranking factor, making image SEO a direct lever for search performance.
5 Ways to Optimize Images for SEO
1. Use Clear and Descriptive Image File Names
When possible, use filenames that are short but descriptive. For example, my-new-black-kitten.jpg is better than IMG00023.JPG. Avoid using generic filenames like image1.jpg, pic.gif, or 1.jpg when possible.
Include a target keyword in the filename to improve search engine visibility, but avoid keyword stuffing. Keep filenames short with keywords at the beginning to make them easily identifiable. Use descriptive and relevant words to help with search engine indexing, and make every word count — do not include stop words such as “a”, “the”, “and”, or “in”.
One practical consideration: once Google crawls your images, it will not re-crawl them for a while, so there is no point in changing existing filenames after the fact. Optimize filenames before uploading.
If your site serves international audiences, when you localize your images, remember to also translate the filenames, keeping the URL encoding guidelines in mind if you are using non-Latin or special characters.
2. Write Keyword-Rich Alt Text and Image Titles
The most important attribute when it comes to providing more metadata for an image is the alt text — text that describes an image — which also improves accessibility for people who cannot see images on web pages, including users who use screen readers or have low-bandwidth connections. Google uses alt text along with computer vision algorithms and the contents of the page to understand the subject matter of the image.
Be descriptive and relevant to help search engines and users. Avoid “picture of” or “photo of” as they add unnecessary words. Use keywords naturally to enhance SEO without keyword stuffing. Keep it concise to ensure clarity and relevance. Use specific language — for example, “Honda Civic” instead of “car” — to provide detailed information.
Avoid using text in images. It does not meet accessibility guidelines as screen readers cannot read it.
When an image is used as a link, be sure to include alternate text relevant to the link’s destination to enhance the user experience.
3. Choose the Right Image Format: WebP and AVIF Are the Current Standard
The original article’s recommendation to use only JPEG and PNG is outdated. Google now supports and actively recommends modern next-generation formats.
AVIF delivers 50% smaller files than JPEG at equivalent quality. WebP provides 25 to 35% savings with near-universal browser support.
WebP has 95% browser support, while AVIF is supported by around 92%.Both formats are now widely supported across modern browsers, making them the practical standard for web image delivery in 2026.
The optimal strategy is to leverage each format where it makes sense. For most sites, this means using AVIF whenever maximum compression or quality is needed, and falling back to WebP for broad compatibility.
To serve both formats with a legacy fallback, use the HTML <picture> element:
html
<picture>
<source srcset=”image.avif” type=”image/avif” />
<source srcset=”image.webp” type=”image/webp” />
<img src=”image.jpg” alt=”Description of the image” width=”1200″ height=”800″ />
</picture>
You can use the Squoosh web app to convert your images to these formats. For WordPress sites, WordPress introduced AVIF support in 2024 on version 6.5, and the Modern Image Formats plugin enables the use of WebP and AVIF image formats for media uploads.
JPEG and PNG still have a role: use JPEG for photographs where legacy compatibility is critical, and PNG only when transparency is required and WebP is not supported.
4. Compress Images and Set Correct Dimensions to Protect Core Web Vitals
Image optimization directly impacts three of Google’s Core Web Vitals metrics — Largest Contentful Paint (LCP), Cumulative Layout Shift (CLS), and Interaction to Next Paint (INP).
Largest Contentful Paint measures how quickly the main content of a web page loads. Images should load in under 2.5 seconds. Cumulative Layout Shift measures visual stability — images that change size while loading cause layout shifts. Prevent this by always setting explicit image width and height attributes.
If the width or height attribute is not set, the browser does not know how much space to reserve for the image during rendering and will reserve 0 pixels for any missing dimension — causing visible layout shifts as the page loads.
Experts generally recommend an image width of about 1200 pixels. Ensure images are high-resolution, as images can appear in many different ways on the search result page — a small thumbnail, a larger preview, within a carousel — so you want images that look good no matter how Google manipulates them.
For Google Discover specifically, use large images at least 1200 pixels wide with the max-image-preview directive. Hero images should be a minimum of 1000 pixels wide with a 16:9 aspect ratio.
For compression tools, TinyPNG specializes in compressing PNG and JPEG files and achieves file size reductions of up to 70% while preserving transparency in PNGs. JPEGmini optimizes JPEG images and reduces file sizes by up to 80%. Google’s PageSpeed Insights is the recommended tool for auditing image performance on your specific pages.
5. Use Lazy Loading, Image Sitemaps, and Structured Data
Lazy Loading
Lazy loading is a web development technique that delays the loading of non-critical resources on a webpage — such as images, videos, or scripts — until they are actually needed by the user. This approach prioritizes the initial loading of essential content while deferring the loading of secondary elements until they come into the user’s view.
Modern browsers support native lazy loading through a single HTML attribute: loading=”lazy”. However, there is one critical rule: you should always avoid lazy loading the LCP element. If a browser has a chance to download the LCP element early during the rendering process, the image will be available to the browser as early as possible and the browser can start painting that element early.
Use fetchpriority=”high” and <link rel=”preload”> for your hero images. Lazy-loading the LCP image is one of the most common performance anti-patterns.
As of 2024, only just above 30% of images use lazy loading — making it one of the easiest performance improvements available to most websites.
Consistent Image URLs
Google has updated its image SEO best practices with guidance on using the same URL when sharing images across a website. If an image is referenced on multiple pages within a larger website, consistently reference the image with the same URL so that Google can cache and reuse the image without needing to request it multiple times.
Image Sitemaps
You can provide the URL of images Google might not have otherwise discovered by submitting an image sitemap. Submitting a dedicated image sitemap ensures Google discovers and indexes all your images, not just those linked from crawled pages — this is critical for eCommerce sites with thousands of product variants.
Structured Data for Images
If you include structured data, Google can display your images in certain rich results, including a prominent badge in Google Images, which gives users relevant information about your page and can drive better targeted traffic to your site. In each of these structured data types, the image attribute is a required field to be eligible for a badge and rich result in Google Images.
By providing structured data, you are helping Google understand the images on your pages. Follow Google’s General Structured Data Guidelines and use the Rich Results Test tool to check if your page supports rich results.
How Image Optimization Affects Page Speed and Core Web Vitals
A good LCP score is 2.5 seconds or less. Websites meeting Core Web Vitals benchmarks see lower bounce rates and higher rankings. Improving LCP can boost conversions by up to 12% for every second saved.
Converting images to WebP or AVIF delivers 25 to 50% savings in page weight. In 2024, roughly 30% of images served use WebP, and fewer than 5% use AVIF — meaning the majority of websites have not yet captured the full performance benefit of modern image formats.
As of May 2024, only 62.1% of websites pass the LCP assessment, leaving room to outpace the competition by meeting the “Good” threshold.
Best Free Tools to Optimize Images for SEO
Several tools are widely used and recommended for image optimization:
Squoosh — Google’s open-source web app for converting and compressing images to WebP and AVIF formats, with a visual quality comparison tool built in.
TinyPNG / TinyJPG — Specializes in compressing PNG and JPEG files, achieving file size reductions of up to 70% while preserving transparency in PNGs. Supports batch processing and offers API access for automation.
Google PageSpeed Insights — Provides mobile and desktop Core Web Vitals scores along with specific recommendations for image and page optimization.
WordPress Plugins — For WordPress sites, plugins like ShortPixel, Imagify, or Smush automatically compress and convert images to optimal formats.
CDNs with Automatic Optimization — Content delivery networks like Cloudflare or Cloudinary offer automatic image optimization and delivery.
Common Image SEO Mistakes to Avoid
Using CSS background images for important content. Google does not index CSS images. Use standard HTML image elements — Google can find images in the src attribute of the <img> element.
Loading images via JavaScript without fallbacks. Execution of on-page JavaScript and rendering often happens later than the first wave of indexing. If lazy loading is set up with an event listener rather than with IntersectionObserver, the JavaScript may never be triggered during Googlebot’s page render.
Using stock photos for featured images. Search engines like Google rank unique images more highly than stock photos found on multiple sites.
Keyword-stuffing file names or alt text. Avoid keyword stuffing in alt text as it results in a negative user experience and your content may be perceived as spam.
Not setting image dimensions. Always specify explicit width and height attributes on every image to prevent Cumulative Layout Shift, which is a confirmed Core Web Vitals ranking signal.
Frequently Asked Questions About Image SEO
What image format is best for SEO in 2026? WebP and AVIF are the 2026 standard. AVIF delivers 50% smaller files than JPEG at equivalent quality, and WebP provides 25 to 35% savings with near-universal browser support.Use the <picture> element to serve AVIF with a WebP fallback and JPEG as the final fallback for older browsers.
What is alt text and why does it matter for SEO? Alt text is text that describes an image and improves accessibility for people who cannot see images on web pages, including users who use screen readers or have low-bandwidth connections. Google uses alt text along with computer vision algorithms and the contents of the page to understand the subject matter of the image.
Should I lazy load all images? No. Lazy loading should only be applied to images below the fold — images that are not immediately visible when a page first loads. Lazy-loading the LCP image is one of the most common performance anti-patterns and should be explicitly avoided. Use fetchpriority=”high” on your hero or LCP image instead.
Do image file names affect SEO? Yes. According to Google Images Best Practices, descriptive, keyword-rich file names are vital for improving your site’s ranking in search engines. They provide search engines with context and improve the chances of your images appearing in image search results.
What is an image sitemap and do I need one? You can provide the URL of images Google might not have otherwise discovered by submitting an image sitemap.It is particularly important for large eCommerce sites or any website where images are loaded dynamically and may not be easily discovered by crawlers through standard HTML links alone.








