Website Image Optimization: Speed and SEO

Boost website speed, SEO rankings, and user experience. Learn how to optimize image properties for better performance and user engagement.

In this article, we’ll cover:

✔️ Why image optimization is crucial
✔️ Best practices for optimizing images (file types, naming, alt text, compression, and more)
✔️ Plugins & tools to automate image optimization
✔️ How to check your website’s updated performance

By the end, you’ll have a fully optimized image strategy to boost your website’s speed and SEO. Let’s dive in!

Why Image Optimization Matters for Website Speed and SEO

Increase User Engagement and Lead Conversion

A delay of even 1 second can lower conversion rates by 7% and increase bounce rates—the percentage of visitors who leave the site after viewing only one page. Optimized images reduce file sizes, making pages load faster for a better user experience.

Effective Search Engine Indexing

Google cannot “see” images, so it indexes them based on filenames, alt text, and metadata. Optimizing image names and attributes is essential for search visibility and SEO rankings.

1. Naming Images for SEO and Page Ranking

Google relies on filenames and alt text to understand images and factor their value into SEO rankings.

Best Practices for Naming Images

Use descriptive, keyword-rich filenames
❌ : IMG12345.jpg
✅ : fluffy-cat-coloring-page.webp
✅ : fluffy-cat-tea-butterfly-coloring-page.webp

Use hyphens, NOT spaces or underscores

✅ : fluffy-cat-tea-butterfly-coloring-page.webp
❌ : fluffy_cat_tea_butterfly_coloring_page.webp
❌ : fluffy cat tea butterfly coloring page.webp

Google treats hyphens (-) as word separators, but spaces and underscores (_) cause issues in indexing.

Use lowercase letters

✅ : fluffy-cat-tea-butterfly-coloring-page.webp
❌ : Fluffy-Cat-tea-butterfly-COLORING-Page.webp
For best SEO and indexing, always use lowercase letters in filenames. Some web servers treat uppercase and lowercase filenames as different files, leading to:

• Duplicate content issues
• Broken links
• Inconsistent SEO strength across versions

2. Optimizing Alt Text for SEO and Accessibility

Alt text improves SEO and accessibility by:
✔️ Helping search engines understand image content
✔️ Assisting visually impaired users via screen readers
✔️ Enhancing Google rankings for relevant search results

Best Practices for Alt Text

Be descriptive but concise
❌ : image of a cat
✅ : Black and white coloring page of a fluffy cat sitting near a tea cup with butterflies flying around.

Include target keywords naturally (avoid keyword stuffing)
❌ : cat, fluffy cat, tea, butterflies, coloring book, cat art, printable coloring page

Length: Keep it under 125 characters for better readability.

Adding Alt Text

To ensure alt text is properly added, it is recommended that you manually add it through your website’s content management system (CMS).

1️⃣ Go to your CMS Media Library (e.g., WordPress Media Library, Shopify Files, Wix Media Manager, Squarespace Image Library).
2️⃣ Click on the image.
3️⃣ Locate the “Alt Text” field.
4️⃣ Enter the desired alt text.
5️⃣ Save changes.

Updating Alt Text of Images Already Placed in Posts and Pages

When you update an image’s alt text in the WordPress Media Library, it does not automatically update on pages or posts where the image has already been placed.

1️⃣ Manually edit the image alt text within each post or page.
2️⃣ Click the image within each post or page and add the new alt text in the post editor.
3️⃣ Save changes.

3. Choosing the Right Image Size

Large images significantly reduce website speed. Start by resizing large images to fit their intended purpose. Whether it is for a banner or a thumbnail, users will only see a set number of pixels based on the monitor and the content container space.

How Pixels Relate to Image Dimensions on a Computer Screen

1️⃣ Pixel Dimensions = Image Size (Width x Height) on a computer monitor

• Standard monitors display images at 1:1 pixel mapping (each pixel in the image matches a screen pixel).
• A 1920 × 1080 px image will completely fill a Full HD (1080p) monitor.
• A 3840 × 2160 px image will fit perfectly on a 4K monitor.
• A 5000 × 5000 px image is larger than most screens, meaning it will be scaled down to fit.
  • Example: If a monitor’s resolution is 1920 × 1080 px, an image larger than 1920 px wide will be resized to fit the screen.
• A 500 × 500 px image will only take up a small portion of the same screen.

2️⃣ Resizing Images to Fit the Display Container

• Images rarely take up the entire screen of a website; instead, the display container (the space where the image is set) dictates the pixel dimensions needed. Images should be sized to match their display container on the webpage. Uploading an image larger than its container slows down page speed without improving quality.
• Check the actual container space for images using your page builder.
  • Example: If a website will display an image within a 600 × 600 px space, but the uploaded image is 4000 × 4000 px, the extra pixels won’t be noticeable—the image will be resized to fit and the large file size will slow load times.
  • Tip: Use Google Lighthouse DevTool in Snapshot Mode. This will generate a list of your image size compared to it’s container size.

Typical Image Parameters

4. Choosing the Right Image Format

Recommended Approach:

• Use PNG for logos to preserve transparency.
• Use WebP for photos, blog images, and thumbnails.
• Use SVG for icons and vector-based graphics.

5. Compress, Convert, & Resize Images for Speed

Free Tools for Image Compression

• TinyPNG for compression of images (WordPress plugin available).
• FreeConvert for converting image files to WebP.
• ImageResizer for reducing pixel size of images.

Automate Image Compression in WordPress

1️⃣ Install the TinyPNG plugin → Automatically compresses new images.
2️⃣ Use Enable Media Replace → Swap old images for optimized versions easily.

Easy Image Conversion, Compression, and Replacement

• Convert images to WebP in bulk for free at FreeConvert.com
• Compress WebP images at TinyPNG.com.
  • Automatically compress uploaded images using the TinyPNG WordPress Plugin
• Automatically replace all instances of an image on your website with its optimized version using the Enable Media Replace WordPress Plugin. This plugin will automatically transfer all links to the new image as well.

6. Check Your Website’s Image Optimization & Speed

Free Tools to Analyze Your Website Performance

• Google Lighthouse DevTool
• Google PageSpeed Insights
  • Free mobile and desktop experience testing.
  • 🎯 Aim for a Google PageSpeed score of 90+ for optimal performance.
• GTmetrix (Free destop experience testing, paid membership required for mobile testing).

Run Website Performance Audits using Incognito Mode

When checking your website’s performance, browser extensions, cached data, and personalized settings can affect results. To get a true reading of how your site performs for new users, run tests in Incognito Mode. By running audits using Incognito Mode, you get clean, unbiased results, allowing for more accurate adjustments to speed and performance.

Steps to test in Incognito Mode:

1. Open a new Incognito window.
   • Google Chrome: Press Ctrl + Shift + N (Windows) or Cmd + Shift + N (Mac).
2. Navigate to the Google Lighthouse DevTool, Google PageSpeed Insights, or GTmetrix.
3. Enter your website URL and run the test.
4. Compare results from a few runs since the results are not static.

Why this helps:

• Ensures accurate page load speeds by bypassing cached assets.
• Removes interference from extensions and ad blockers that might impact rendering.
• Simulates a first-time visitor experience, giving you insight into how new users perceive your site.

Final Thoughts: Best Practices Summary

✔️ Use PNG for logos, WebP for everything else
✔️ Resize images for their display container before uploading
✔️ Compress images using tools like TinyPNG
✔️ Use SEO-friendly filenames and alt text
✔️ Analyze website performance

By following these steps, your website will load faster, rank higher, and convert better. 🚀

This article is for informational and entertainment purposes only and does not constitute professional advice. Please consult a qualified professional for your specific needs. Swirly Sky Ventures LLC assumes no responsibility or liability for any actions taken based on the information provided in this article. For more details, please review our Terms of Use.

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