Image SEO: Alt Text, File Names, Compression & Format Guide

Images can drive significant traffic through Google Image Search, but only if they are properly optimized for search engines. Here is what actually matters.

Descriptive File Names

Search engines read file names. "IMG_4523.jpg" tells Google nothing. "blue-ceramic-coffee-mug-on-wooden-table.webp" tells it exactly what the image shows.

File Name Best Practices

• ●Use descriptive, keyword-rich names
• ●Separate words with hyphens (not underscores)
• ●Keep names concise but informative
• ●Include the primary keyword naturally
• ●Use lowercase letters only

Alt Text

Alt text serves two purposes: accessibility (screen readers read it to visually impaired users) and SEO (search engines use it to understand image content).

Writing Good Alt Text

• ●Describe what the image actually shows
• ●Include relevant keywords naturally — do not stuff them
• ●Keep it under 125 characters
• ●Do not start with "image of" or "picture of" — screen readers already announce it as an image
• ●Be specific: "Golden retriever puppy playing in autumn leaves" not "dog"

When to Leave Alt Text Empty

Decorative images that add no informational content (background patterns, dividers) should have empty alt text: alt="". This tells screen readers to skip them.

Image Compression for SEO

Page speed is a direct ranking factor. Uncompressed images are the most common cause of slow pages.

Target File Sizes

• ●Hero images: under 200 KB
• ●Content images: under 100 KB
• ●Thumbnails: under 30 KB

Use ImgGPT's compressor with WebP output to hit these targets consistently.

Modern Image Formats

Google recommends WebP and AVIF for web images. Pages that use modern formats score higher on PageSpeed Insights, which correlates with better rankings.

Convert your images to WebP with ImgGPT's converter. For maximum compatibility, serve WebP with a JPG fallback using the picture element.

Image Sitemaps

If images are important to your site (e-commerce, photography, stock photos), add them to your sitemap. This helps Google discover and index images that might be loaded dynamically or embedded in JavaScript.

Structured Data

For product images, recipe images, and other specific types, schema.org structured data helps Google understand context. Add image properties to your existing schema markup.

Google Image Search Optimization

To appear in Google Image Search results:

• ●Use descriptive file names and alt text
• ●Ensure images are on publicly accessible pages
• ●Use high-quality images (blurry or tiny images are filtered out)
• ●Place images near relevant text content
• ●Use proper image sitemaps
• ●Ensure fast page load times

The SEO Image Workflow

For every image you publish:

• ●Rename with descriptive, hyphenated keywords
• ●Resize to display dimensions
• ●Compress to target file size
• ●Convert to WebP
• ●Write descriptive alt text
• ●Place near relevant content

This workflow takes seconds per image and makes a measurable difference in search visibility.