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Image Optimization Guide: Boost LCP and Core Web Vitals

6 min read

January 23, 2026

image optimization, core web vitals lcp, reduce image size

Images are responsible for 60-80% of the average webpage's payload. If your site is loading slowly, unoptimized images are likely the culprit.

This guide explains how to optimize images to improve your Largest Contentful Paint (LCP) score—a critical Google ranking factor—without sacrificing visual quality.

Why Image Size Matters for SEO#

Google's Core Web Vitals update made speed a direct ranking factor. The most important metric is:

LCP (Largest Contentful Paint): How long it takes for the main content (usually a hero image) to load.

The Benchmark: Google requires an LCP of under 2.5 seconds for a "Good" score. Large, uncompressed images can easily take 3-4 seconds to load on mobile networks, killing your rankings.

JPG vs PNG vs WebP: Using the Right Format#

Choosing the right file format is the first step in optimization.

Format	Best Use Case	Pros	Cons
JPG	Photos, complex gradients	Smallest file size	Lossy (artifacts)
PNG	Screenshots, transparency	Lossless quality	Huge file sizes
WebP	Modern web standard	Mixed pros of JPG/PNG, 30% smaller	Legacy browser support (rare)
SVG	Icons, logos	Infinite scaling, tiny size	Vectors only

Lossy vs Lossless Compression#

Lossless Compression reduces file size by removing metadata (EXIF data) and optimizing encoding. Quality remains 100% identical.

Lossy Compression (what we use in our Image Compressor) intelligently removes data perceived as "noise" by the human eye. You can typically reduce a file by 70-80% with zero visible difference.

Responsive Sizing#

Never serve a 4000px wide image to a mobile phone. Resize your images to the maximum display width needed.

Desktop Hero: Max 1920px width
Blog Content: Max 800-1200px width
Thumbnails: Max 400px width

Use our Image Resizer to generate multiple versions of your assets.

Frequently Asked Questions

Does WebP improve SEO?▼

Indirectly, yes. WebP files are smaller than JPGs, loading faster. Faster load times improve your Core Web Vitals score, which typically improves search rankings.

What is the ideal file size for a web image?▼

Aim for under 100KB for large hero images, and under 30KB for smaller content images. Anything over 200KB should be compressed immediately.

Do I need alt text for every image?▼

Yes! Alt text is critical for accessibility (screen readers) and helps search engines understand the content of your images for Google Images search.

Optimize Your Images Now

Reduce file sizes by up to 80% instantly. Secure, client-side compression that never uploads your photos to a server.

Compress Images Free

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