List of Important SEO Tags | Types, Roles, and How to Write Them Explained Together

"Tags are important for SEO" is often said, but there are many types of tags, each with a different role and way of writing. Many people may be unable to get started, unsure of which tags to focus on or how to write them to lead to SEO effects. This article organizes the important tags for SEO in a list and explains the type, role, and writing points of each one together.

What Are "Tags" in SEO?

In SEO, tags are HTML descriptions that correctly convey a web page's content and structure to search engines and browsers. Tags are broadly divided into "meta-information tags (such as title and meta description)" that convey how the page appears in search results and its settings, and "content tags (such as h tags and a tags)" that show the structure and meaning of the body text.

What is important is that tags themselves do not directly raise rankings. Tags are "clues" for search engines to correctly understand a page and display it appropriately in search results. Setting them correctly supports the evaluation of the entire site through paths such as promoting crawler understanding, improving click-through rate, and preventing duplication.

Tags Related to How You Appear in Search Results

title Tag

The title tag is the title part displayed prominently in search results and one of the most important tags for SEO. It conveys page content to both search engines and users. The writing points are to place the target keyword as close to the beginning (left side) as possible and keep it to about 30–35 full-width characters. If it is too long, the end is omitted in search results, and Google becomes more likely to rewrite the title. Set a unique title for each page.

meta description Tag

The meta description is the explanatory text (snippet) displayed below the title in search results. It has no direct impact on rankings, but an attractive sentence can be expected to improve the click-through rate (CTR). Summarize the page content in about 100–120 characters and match it to the search intent. Rather than reusing it across all pages, it is important to set a unique description for each page. Note that Google sometimes automatically generates a snippet from the body text according to the search query.

Tags Related to Page Structure and Body Text

h Tags (Headings: h1–h6)

h tags are heading tags corresponding to a book's table of contents or chapter structure, ranging from h1 to h6, with smaller numbers representing larger headings. h1 indicates the page's main subject, with one per page as the basic rule. By naturally including search keywords in headings and keeping the hierarchical order of h2 → h3 → h4, the page's logical structure is more easily conveyed to Google. Avoid stuffing keywords, as it is counterproductive.

a Tag (Link)

The a tag is used to link to another page or URL. It is both a means of movement for users and a route for crawlers to traverse between pages. The point is to use words for the link text (anchor text) that make the linked content clear. Rather than a link that just says "here," using an expression that concisely indicates the content makes the link destination clearer to both users and search engines.

img / alt Attribute (Alternative Text for Images)

For the img tag that displays an image, set text describing the image's content with the alt attribute. Because search engines cannot directly understand the image itself, alt is an important clue that conveys the image's content, and it is also useful from the perspective of image search and accessibility. Describe the image's content concisely and avoid forced keyword stuffing.

strong Tag (Emphasis)

The strong tag is used to make text bold and emphasize its importance. Emphasizing important keywords can be expected to convey the importance of those words to Google. However, overusing it makes it hard to judge what is truly important, so a guideline of a few places per section is appropriate. If you simply want bold-looking text, use CSS, and limit strong to the points you most want to emphasize.

Tags That Control Search Engine Behavior

canonical Tag (URL Normalization)

The canonical tag tells search engines "this is the canonical URL you should evaluate" when there are multiple pages with similar content. It prevents the dispersion of evaluation when duplication arises from http vs. https, with/without www, URL parameter differences, similar pages auto-generated by a CMS, and so on. As a basic rule, setting each page's own URL as canonical helps prevent unexpected duplicate content.

meta robots / viewport, etc.

meta robots is a tag that instructs crawler behavior, such as not indexing a specific page (noindex). viewport is a specification for optimizing smartphone display; if unset, it is judged as a deficiency in mobile support and evaluation may indirectly drop. At minimum, it is recommended to set title, description, canonical, and viewport.

Tags That Are Unnecessary or Low Priority

The "meta keywords" tag, once a staple of SEO, is no longer used by major search engines such as Google and Bing for ranking judgment. Setting it does not cause a penalty, but no SEO effect can be expected, and there is even the downside of exposing your target keywords to competitors. New setup is unnecessary; spend that time raising the quality of your content.

Tags' Growing Importance in the AI Search Era

In recent years, AI search and summarization by generative AI have spread, and the importance of tags as machine-readable signals has, if anything, increased. In particular, title and meta description are said to be referenced as judgment material when AI summarizes or cites page content. Furthermore, by maintaining them together with OGP (tags that arrange the display when shared on social media) and structured data, information is more easily conveyed correctly to both search engines and AI.

Summary

The important tags for SEO can be organized into title and meta description, which determine how you appear in search results; h tags, a tags, alt, and strong, which convey page structure; and canonical, robots, and viewport, which control search engine behavior. None of them raise rankings on their own; they function as the foundation for search engines to correctly understand a page.

First, on your site's main pages, start by checking whether the target keyword is appropriately included in the title and h tags, and whether meta description and canonical are set correctly. Correctly arranging the basic tags is the first step in SEO that makes the most of your content's quality.