Lesson 16
Image Filenames & Alt Text: Simple Rules
What you’ll learn
By the end of this lesson, you’ll understand:
Why image filenames and alt text matter
How to write alt text properly
What to avoid when describing images
Why images matter for SEO
Images help:
- Support written content
- Improve readability
- Provide context
Search engines can’t “see” images in the way humans do, so they rely on textual clues to understand what an image represents.
That’s where filenames and alt text come in.
Image filenames: keep them simple
Before uploading an image, give it a clear, descriptive filename.
For example:
❌ IMG_2847.jpg
✅ on-page-seo-headings-example.jpg
Good filenames:
- Use real words
- Separate words with hyphens
- Reflect what the image actually shows
You don’t need to over-optimise — clarity is enough.
What alt text is for
Alt text:
- Describes the image for screen readers
- Provides context if the image fails to load
- Helps search engines understand the image’s role
Alt text is primarily about accessibility, with SEO as a secondary benefit.
How to write good alt text
Good alt text:
- Describes what’s in the image
- Is concise and specific
- Fits naturally in a sentence
For example:
“Example of an H2 heading used to structure a blog post”
If the image is decorative and adds no meaning, alt text can be left empty.
What to avoid
Avoid:
- Keyword stuffing
- Describing what’s already obvious in surrounding text
- Writing alt text for purely decorative images
- Using the same alt text for multiple images
Alt text should help someone understand the image — nothing more.
A helpful test
Ask:
“If I couldn’t see this image, what would I need to know?”
That’s your alt text.