On-Page SEO Checklist: A Developer's Guide

Published on: by Dr. Talib

Search Engine Optimization (SEO) isn't just for marketers. As developers, the code we write forms the technical foundation of a website's search performance. By following a few best practices, we can ensure our pages are perfectly structured for Google and other search engines to understand. Here is a practical checklist of on-page SEO factors every developer should know.

1. The Title Tag (`<title>`)

The Goal: This is the single most important on-page SEO factor. It becomes the clickable headline in search results.

The Checklist:

  • Is it unique for every page?
  • Does it accurately describe the page's content?
  • Is it between 50-60 characters long?
  • Does it include the primary keyword you want the page to rank for, preferably near the beginning?
<!-- Excellent -->
<title>CSS Flexbox: A Beginner's Guide | HTML Viewer</title>

<!-- Weak -->
<title>Guide</title>

2. The Meta Description (`<meta name="description">`)

The Goal: While not a direct ranking factor, the meta description is your sales pitch in the search results. A compelling description encourages users to click on your link over a competitor's.

The Checklist:

  • Is it unique for every page?
  • Is it a compelling summary (an "ad") for the page's content?
  • Is it between 150-160 characters long?
  • Does it include a call to action or your target keyword naturally?
<meta name="description" content="Learn the fundamentals of CSS Flexbox with clear, interactive examples you can test in our live editor. Master modern layouts today.">

3. Heading Structure (`<h1>`, `<h2>`, etc.)

The Goal: Headings create a logical hierarchy for your content, which is useful for both users and search engines. Think of them as the outline for your page.

The Checklist:

  • Is there exactly one <h1> tag on the page, representing the main title?
  • Do the subheadings (<h2>, <h3>) follow a logical order without skipping levels (e.g., don't jump from an <h2> to an <h4>)?
  • Do headings naturally include relevant keywords and subtopics?

Test your structure: Use the HTML Viewer to build a simple document structure. It's easy to see how a clean hierarchy with `h1` through `h3` is more readable than one with random heading levels.

4. Image SEO (`alt` text)

The Goal: Search engines can't "see" images. The `alt` attribute provides the textual context they need to understand and index your images, which can drive traffic from image search.

The Checklist:

  • Does every meaningful image have a descriptive `alt` attribute?
  • Does the `alt` text accurately describe the image content?
  • Are purely decorative images given an empty alt attribute (alt="") so they are ignored by assistive tech?
<img src="debugging-diagram.png" alt="Diagram showing the CSS Box Model with content, padding, border, and margin.">

5. Site Performance and Mobile-Friendliness

The Goal: Google prioritizes sites that offer a good user experience. This means your site must be fast and work well on mobile devices.

The Checklist:

  • Have you included the viewport meta tag (<meta name="viewport" ...>)?
  • Are you using responsive design techniques (like Media Queries) so the layout adapts to small screens?
  • Are your images optimized and compressed to reduce load times?
  • Does your site pass Google's PageSpeed Insights test?

SEO is a Feature, Not an Afterthought

By treating these on-page factors as a core part of your development process, you ensure that every page you build has a strong technical foundation for search engine success. Clean, semantic, and performant code is the best SEO you can write.