The placement of <script> tags in HTML markup depends on your specific needs, modern best practices now favor using the async and defer attributes to allow scripts to load without blocking page rendering. While traditionally placed at the bottom of the <body> element, the optimal approach varies based on script importance and dependencies.

Traditional Script Placement

Historically, developers placed <script> tags at the bottom of the <body> element before the closing </body> tag. This approach became popular for several reasons:

Why bottom of body was preferred: Script tags inside the head element will be loaded and interpreted before any HTML is rendered, this blocks HTML/CSS rendering. Script tags at the bottom of the body tag will not block HTML/CSS and since you can only play around with the DOM after it’s been built.

However, this traditional approach has significant limitations:

Delayed Loading: The browser cannot start downloading scripts until the very end of HTML parsing
Sequential Loading: Scripts load one after another rather than in parallel
Render Blocking: While better than head placement, it still delays script execution until DOM parsing completes

According to the Stack Overflow discussion, this “old approach to solve this problem was to put <script> tags at the bottom of your <body>, because this ensures the parser isn’t blocked until the very end.”

Modern Script Loading Strategies

The modern approach leverages the async and defer attributes to optimize script loading without sacrificing functionality:

Async Attribute

html

<script src="analytics.js" async></script>

Downloads the script without blocking HTML parsing
Executes as soon as the download completes (out of order)
Best for independent scripts that don’t depend on other scripts
According to MDN documentation, “It is best to use async when the scripts in the page run independently from each other and depend on no other script on the page”

Defer Attribute

html

<script src="jquery.js" defer></script>
<script src="app.js" defer></script>

Downloads the script without blocking HTML parsing
Executes in the order they appear in the document after DOM parsing is complete
Best for scripts that depend on each other or need access to the complete DOM
As JavaScript.info explains, “the browser is instructed to download the script in the background while it continues to parse the HTML document”

Attribute Precedence

If both async and defer are specified, async takes precedence on modern browsers, while older browsers that support defer but not async will fallback to defer.

jQuery-Specific Recommendations

For jQuery specifically, modern practices have evolved:

Traditional jQuery Placement

html

<!-- Old approach - bottom of body -->
<script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
<script src="your-app.js"></script>
</body>

Modern jQuery Placement with Defer

html

<!-- Modern approach - head with defer -->
<head>
  <script src="https://code.jquery.com/jquery-3.6.0.min.js" defer></script>
  <script src="your-app.js" defer></script>
</head>

According to expert advice, “library script such as the jQuery library” can be placed in the head section, especially when using defer to prevent blocking.

Critical Scripts in Head

For scripts that are critical to page contents and should be loaded first such as analytics, API, or authentication-type of scripts, “it is recommended to place them in the head section of the HTML page” with async or defer.

Performance Implications

Script placement significantly impacts page performance:

Head Placement (Without Async/Defer)

Pros: Scripts load early
Cons: Blocks HTML/CSS rendering completely
Use Case: Only for very small, critical scripts

Body Bottom Placement (Traditional)

Pros: Doesn’t block rendering
Cons: Delays script loading and execution
Use Case: Legacy sites or when async/defer aren’t supported

Head with Async/Defer

Pros: Early download without blocking rendering
Cons: Requires understanding execution order
Use Case: Modern websites with proper dependency management

As noted in the research, “Place <script> tags in <head> with async or defer to start fetching early, or at the end of <body> for scripts without these attributes.”

Practical Implementation Guide

Step-by-Step Best Practice Implementation

Identify Script Dependencies
- Critical scripts (analytics, authentication)
- Library dependencies (jQuery, frameworks)
- Application logic
- Third-party integrations

Choose Loading Strategy

html

<!-- Critical independent scripts -->
<script src="critical-script.js" async></script>

<!-- Scripts that depend on others -->
<script src="jquery.js" defer></script>
<script src="app.js" defer></script>

Place Based on Strategy

html

<head>
  <!-- Critical scripts with async -->
  <script src="analytics.js" async></script>
  
  <!-- Deferred scripts -->
  <script src="jquery.js" defer></script>
</head>

<body>
  <!-- Page content -->
  
  <!-- Non-critical scripts without async/defer -->
  <script src="legacy-script.js"></script>
</body>

Performance Optimization Tips

Use fetchpriority="high" for critical scripts
Minimize inline scripts in head
Consider module scripts for modern applications
Use CDN hosting for better caching

When to Use Each Approach

Scenario	Recommended Placement	Rationale
Critical analytics	Head with `async`	Early loading, independent execution
jQuery + dependent scripts	Head with `defer`	Maintains execution order, early download
Third-party trackers	Bottom of `body`	Legacy compatibility, non-critical
Legacy applications	Bottom of `body`	Maximum browser compatibility
Modern SPAs	Head with `defer` or `async`	Optimized loading, better performance

According to web development experts, “Scripts that enhance functionality but are not essential for the initial page rendering can be placed at the bottom, just before the closing </body> tag.”

Common Mistakes to Avoid

Mixing Blocking and Non-Blocking Scripts
- Don’t place some scripts in head without async/defer and others in body
- This creates unpredictable loading patterns
Ignoring Script Dependencies
- Using async on scripts that depend on each other
- Not considering execution order with defer
Overusing Inline Scripts
- Large inline scripts in head block rendering
- Move to external files with proper loading attributes
Forgetting Browser Compatibility
- Not testing async/defer behavior in older browsers
- Not providing fallbacks for critical functionality

As Reddit developers note, “Good practice is to take it into the head and use async or defer. For older browsers it’s common to put it after the body tag.”

Conclusion

The optimal placement of <script> tags in HTML has evolved significantly with modern web development practices. Here are the key takeaways:

Modern Best Practice: Use async and defer attributes to place scripts in the <head> without blocking rendering
jQuery Placement: Can go in head with defer attribute for early loading while maintaining execution order
Critical Scripts: Place in head with async for independent, early-loading functionality
Legacy Scripts: Bottom of body remains acceptable for non-critical scripts without loading attributes
Performance Focus: Prioritize early download with non-blocking attributes over traditional placement

The right approach depends on your specific needs, but modern web development favors intelligent script loading strategies over simple placement rules. By understanding the performance implications and using appropriate loading attributes, you can optimize both page load times and functionality.

Sources

Does the

Contents

Traditional Script Placement

Modern Script Loading Strategies

Async Attribute

Defer Attribute

Attribute Precedence

jQuery-Specific Recommendations

Traditional jQuery Placement

Modern jQuery Placement with Defer

Critical Scripts in Head

Performance Implications

Head Placement (Without Async/Defer)

Body Bottom Placement (Traditional)

Head with Async/Defer

Practical Implementation Guide

Step-by-Step Best Practice Implementation

Performance Optimization Tips

When to Use Each Approach

Common Mistakes to Avoid

Conclusion

Sources

Script Tag Placement: Head vs Body Performance Guide