Images are a hidden gateway to search traffic. The once text-centric search landscape is rapidly expanding to include image search, shopping carts, AI summaries, and visual answers. Search engines and AI don't "see" images. Instead, they read ALT tags. ALT tags are the starting point of image SEO and a text interface that simultaneously influences accessibility, trustworthiness, and citation potential.

What is an ALT tag?

Alternative Text (ALT) tags are text that describes an image when the image doesn't load or when a screen reader is used. Search engines use ALT tags to understand the meaning and context of an image and use them to determine image search results and page topics. In other words, ALT tags are not a "caption" for an image, but rather a description of its meaning.

Key Principles of Good ALT Tags

First, accurately describe the image. Describe exactly what you see, but capture only the essential points within the context of the page.

Second, use natural sentences. Avoid listing keywords and write sentences that are understandable to a human reader.

Third, avoid duplication. Even for the same image, the ALT value may vary depending on the page context.

Fourth, eliminate unnecessary expressions. Using single words like "image," "photo," or "picture" is meaningless.

How should keywords be included?

ALT tags aren't intended as a keyword slot. They should only be included if the image naturally illustrates the keyword. For example, for product photos, focus on the product name and key attributes, while contextual images should focus on the action or scene. Keywords are intended as a result, not a goal.

Example of writing ALT tags according to situation

• Product Image: Men's business backpack in black leather.
• Service Screen Capture: Screen showing page performance in the admin dashboard.
• Infographic: A step-by-step diagram illustrating the search engine crawling and indexing process.
• Decorative images: If there is no meaning to convey, treat it as an empty ALT ("").

The Relationship Between ALT Tags and Accessibility

ALT tags are a key element of web accessibility, even before SEO. By converting visual information into text, they make content more accessible to a wider audience. Sites that consider accessibility are also perceived by search engines as "responsible information providers," which builds trust over the long term.

Impact on companies and brands

Images on a corporate website convey brand messages, product information, and service flow. If ALT tags are empty or inaccurate, this information will be lost to search engines and AI. Conversely, well-designed ALT tags simultaneously increase image search traffic, AI citations, and SERP feature exposure.

Checklist for practical use

• Mandatory ALT input when uploading images
• Distinguishing between decorative and informational images
• Contextual ALT check when using the same image repeatedly
• Regularly check for missing ALT images in your CMS
• Auto-generated ALT must be reviewed

Insight Summary

ALT tags are invisible, but they provide the clearest description to search engines and AI. Simply creating a good image isn't enough. It must be accompanied by text that conveys the image's meaning. Image SEO isn't a matter of design, but of interpretation. The moment you properly create ALT tags, your image becomes a search asset, not just decoration.