How To Optimize Images In HTML For SEO

Images play a powerful role in website engagement, design, and content value—but they are also the #1 reason behind slow page speed, poor LCP scores, and weak Google rankings.
If your images are not properly optimized, your website will struggle to achieve strong SEO performance, no matter how good your content is.

In this complete guide, you will learn how to optimize images in HTML for SEO, using modern formats like WebP, compression techniques, lazy loading, responsive images, and proper HTML attributes to significantly boost Core Web Vitals.

This is a fully updated 2025 guide, written in a human-friendly tone, and integrates advanced image optimization strategies that Google prefers today.

Why Image Optimization in HTML is important for SEO

Images impact almost every major Google ranking factor:

Page Speed & Core Web Vitals Improvement

Heavy JPG/PNG images slow down the Largest Contentful Paint (LCP).
Google ranks faster pages higher because fast loading = better user experience.

Better Indexing & Discovery

Optimized images help Google understand your content through:

File names
Alt text
Structured HTML
Responsive image attributes

Higher Rankings in Google Images

Image SEO helps you appear in:

Google Images
Visual Search
SERP Featured Images

Lower Bounce Rate

Fast-loading visuals keep users on your site longer.

12 Steps Image Optimization in HTML

Step 1 — Use the Right Image Format

Best Format for SEO in 2025: WebP

WebP provides:

30–50% smaller file sizes
Faster loading
Higher quality
Better LCP performance

Example:

Format	File Size	Speed	SEO Impact
PNG	Large	Slow	Poor
JPEG	Medium	Good	Good
WebP	Smallest	Fastest	Best

Always upload WebP as your primary format, with JPG as fallback.

Step 2 — Compress Your Images Before Uploading

Uncompressed images kill page speed.

Recommended Compression:

JPG: 70–80% quality
WebP: 70% quality
PNG: Use only when transparency is required

Tools:

Squoosh
TinyPNG
Compressor.io
Photoshop Export for Web

This step alone can cut image file sizes by 60–80%.

Step 3 — Resize Images to the Proper Dimensions

Never upload a 5000px image if your blog shows it at 1200px.

Ideal Sizes:

Blog featured image: 1200px width
In-post image: 800–1000px
Thumbnails: 300–500px

This prevents mobile users from downloading unnecessarily large files.

Step 4 — Use SEO-Friendly File Names

Google reads file names like keywords.

Wrong:
IMG_00342.jpg

Correct:
optimize-images-html-for-seo.webp

Your file name should describe the image clearly and naturally.

Step 5 — Optimize Alt Text Properly

Alt text improves:

SEO
Accessibility
Google Image visibility

Example:

<img src=”optimized-image.webp” alt=”How to optimize images in HTML for SEO” />

Do NOT keyword-stuff alt text.

Learn more about alt usage: What Is an Anchor Tag in HTML

Step 6 — Add Width & Height Attributes (Prevents CLS)

Cumulative Layout Shift (CLS) happens when content jumps while loading.

Fix this by adding fixed dimensions:

<img src=”image.webp” width=”1200″ height=”600″ alt=”Image SEO example”>

This stabilizes layout and improves Core Web Vitals.

Step 7 — Use Lazy Loading for Images Below the Fold

Lazy loading tells the browser to load images only when users scroll near them.

<img src=”blog-image.webp” loading=”lazy” alt=”Lazy loading image example”>

Do NOT lazy-load hero images—they affect LCP.

Know more: Lazy Loading Images Guide

Step 8 — Use the Picture Tag for Modern SEO & Browser Compatibility

Serve WebP first, with JPEG fallback for older browsers:

<picture>

<source srcset=”image.webp” type=”image/webp”>

<source srcset=”image.jpg” type=”image/jpeg”>

<img src=”image.jpg” alt=”HTML image optimization example” width=”1200″ height=”600″>

</picture>

This improves:

Performance
Browser compatibility
Image SEO

Step 9 — Add Responsive Images with srcset & sizes

Mobile users should not download desktop-size images.

<img

src=”image-800.jpg”

srcset=”

image-400.jpg 400w,

image-800.jpg 800w,

image-1200.jpg 1200w”

sizes=”(max-width: 600px) 100vw, 800px”

alt=”Responsive image example”

>

This is one of Google’s strongest image SEO recommendations.

Step 10 — Preload Your LCP Image

Preloading boosts LCP and helps your page load significantly faster.

<link rel=”preload” as=”image” href=”hero.webp” fetchpriority=”high”>

Use only on your main above-the-fold image.

Step 11 — Prevent Render-Blocking Issues from Images

Unoptimized image delivery delays rendering.

Fix rendering issues using this guide:Eliminate Render-Blocking Resources in WordPress

Step 12 — Interlink Important Image SEO Articles

Internal links help Google understand context better.

Recommended articles (add inside the blog naturally):

Why Page Speed Matters
Anchor Tags for SEO
Lazy Loading
Render Blocking Resources
How to Insert an Image in HTML

Especially this one: How to Insert an Image in HTML

Final Checklist Before Publishing

Convert images to WebP
Compress & resize before uploading
Use descriptive file names
Write clean alt text
Add width and height
Enable lazy loading (below fold)
Use picture + srcset
Preload hero image
Audit with PageSpeed Insights

Following this checklist ensures:

Faster LCP
Lower CLS
Better indexing
Higher rankings
Stronger user experience

Image Optimization Is Now Essential for Ranking on Google

Image optimization is no longer optional—it is a major ranking factor that directly impacts your Core Web Vitals, discoverability, and user experience.
By applying the HTML techniques, compression methods, and SEO practices mentioned in this guide, your website becomes significantly faster, more accessible, and more competitive on Google.

If you follow these steps consistently, you’ll see improvements in:

Page speed
Search visibility
Engagement
Conversions
Overall SEO performance

Your images won’t just look beautiful—they’ll work for your rankings.