How to Optimize Images for SEO: A Practical 2026 Checklist

By ToolNexus Team

Most advice on how to optimize images for seo opens with alt text. That is the wrong end. Alt text is worth doing and it will not fix a page carrying eleven megabytes of photographs. This checklist runs in the order that actually moves the numbers, heaviest lever first.

Quick Answer at a Glance

Six steps, in this order. Doing them out of order wastes effort, because each one changes what the next one has to work with.

Step 1: Resize Before Anything Else

This is where nearly all the weight lives and it is the step people skip.A photograph straight off a phone is often 4000 pixels wide. Displayed in a column 800 pixels wide, the browser downloads all four thousand and throws three quarters of them away on arrival. Resizing to the width you actually display removes roughly nine tenths of the data before any other step touches the file.Serve at double the display width if you support high resolution screens. That means 1600 pixels for an 800 pixel column. Beyond that you are paying for pixels nobody will ever see.

Step 2: Pick the Format

Photographs to WEBP with a JPG fallback. Graphics, screenshots and anything with text to WEBP or PNG. Logos and icons to SVG.Google measures lossy WEBP at 25 to 34 percent smaller than an equivalent JPEG. This step alone removes about a third of what remains after resizing. The full reasoning for each format sits in best image format for web. The specific graphics decision is in webp vs png.

Step 3: Compress What Is Left

Now compression has something sensible to work on rather than a 4000 pixel original.Run files through the tool that will compress jpeg and PNG images. Moderate settings are almost always right. The mechanics of why are in lossy vs lossless compression.Targets worth aiming at. Hero banners under 200 KB. Article images under 100 KB. Product photographs under 150 KB. Thumbnails under 30 KB. Anything on a page above 1 MB is costing you mobile visitors.

Step 4: Name the File Like a Human

IMG_20260902_143755.jpg tells a search engine nothing. blue-ceramic-mug-handmade.jpg tells it quite a lot.

Use hyphens rather than underscores, keep it short, describe what is actually in the picture. This is a small signal rather than a large one. It costs nothing at upload time and is tedious to fix later across a whole site.

Step 5: Write Alt Text That Earns Its Place

Alt text exists for people using screen readers. Search engines read it as a description of the image, which is why it helps. That order matters when you write it.Describe the image as you would to somebody on the phone. Blue ceramic mug with a curved handle on a wooden table. Not mug buy mugs cheap mugs online. Keyword stuffed alt text reads badly to a screen reader user and is easily detected as manipulation.Decorative images that carry no information should have an empty alt attribute rather than a description. Screen readers then skip them instead of announcing something meaningless.

Step 6: Lazy Load Below the Fold

Lazy loading tells the browser to fetch an image only when the reader scrolls near it, which removes off-screen images from the initial page load entirely.One rule protects you from the common mistake. Never lazy load the image at the top of the page. That image is usually what Google measures as your largest contentful paint. Delaying it makes the score worse rather than better. Lazy load everything below the fold and load the top image eagerly.

What Actually Gets Measured

Google’s Core Web Vitals assess loading, interactivity and visual stability. Images touch two of the three directly.Largest contentful paint is usually a picture. Its weight and its loading behavior set that score. Cumulative layout shift is caused by images without declared width and height, because the browser cannot reserve space and the text jumps when the picture arrives. Setting those two attributes on every image is a one line fix with a measurable result.

The Order Matters More Than the List

Compressing before resizing wastes most of the saving, because you spend effort squeezing pixels you were about to delete. Writing alt text on a page that takes nine seconds to load is polishing something nobody waits to see.Work down the impact column. On most sites steps one to three deliver ninety percent of the result and take an afternoon. Steps four to six are worth doing and belong after the heavy lifting.

A Real Case

A recipe blog had thirty photographs on a popular post, all uploaded straight from a camera. The page weighed 41 MB. Resizing to 1200 pixels and converting to WEBP brought it under 3 MB. No compression settings were touched and nothing looked different. The two steps took about forty minutes.

A Note for iPhone Photographers

Photographs from a recent iPhone arrive as HEIC, which most content systems still handle badly. Convert them before uploading rather than afterwards. The methods are in how to convert heic to jpg.

About the Author

The ToolNexus Team builds free browser based file tools. The site started with a small group of developers who thought professional grade utilities should not carry a professional grade price tag. It now runs ten tools covering images, PDFs, video and code.

FAQs About how to optimize images for seo

Start at the Top of the List

Resize, convert, compress. Those three take an afternoon and deliver most of the result. Names, alt text and lazy loading come after, once the page is no longer heavy. Every tool you need for the first three is free on ToolNexus with no account.