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@http-equiv : The HTTP Header Equivalent Attribute

The http-equiv attribute provides an HTTP header equivalent for HTML <meta> elements. In web contexts, it instructs browsers to behave as if a specific HTTP header was received. In PDF generation, it is primarily informational and maintains HTML compatibility.

Usage

The http-equiv attribute is used with <meta> elements to:

  • Declare document character encoding (though charset is preferred)
  • Specify content type information
  • Provide HTTP-header-like directives
  • Maintain web-to-PDF conversion compatibility
  • Document intended HTTP behavior
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
</head>

Supported Elements

The http-equiv attribute is supported by the following element:

Element Description
<meta> Metadata element for document properties

Attribute Values

Syntax 

<meta http-equiv="directive" content="value" />

Common Values

Value Content Description PDF Behavior
Content-Type text/html; charset=UTF-8 Declares document MIME type and encoding Informational only
X-UA-Compatible IE=edge Browser compatibility mode Ignored in PDF
refresh 30; url=... Page refresh/redirect Not applicable to PDF
default-style stylesheet-name Preferred stylesheet Not commonly used
Content-Language en-US Document language Informational

Binding Values

The http-equiv and content attributes support data binding:

Static Declaration 

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />

Dynamic Value 

<!-- Model: { charset: "UTF-8", language: "en-US" } -->
<meta http-equiv="Content-Type" content="text/html; charset=" />
<meta http-equiv="Content-Language" content="" />

Notes

Web Behavior vs PDF Behavior

In Web Browsers:

  • http-equiv directives are processed as if they were HTTP headers
  • Affects browser rendering, caching, and behavior
  • Can trigger specific browser modes or actions

In Scryber PDF Generation:

  • http-equiv attributes are informational only
  • No HTTP headers are generated (PDFs are not served via HTTP)
  • Maintains HTML document structure for compatibility
  • Character encoding is handled automatically

Character Encoding

While http-equiv="Content-Type" can specify character encoding, the standalone charset attribute is preferred:

<!-- Old style (still valid) -->
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />

<!-- Modern style (recommended) -->
<meta charset="UTF-8" />

Limited Applicability

Most http-equiv directives are not applicable to PDF generation:

  • refresh: PDFs are static documents
  • X-UA-Compatible: No browser rendering involved
  • Cache control directives: PDFs are files, not served resources

Use Cases in PDF

  1. Documentation: Preserve original HTML meta information
  2. Compatibility: Maintain structure when converting web pages
  3. Standards Compliance: Follow HTML specifications
  4. Metadata: Provide additional document context

Examples

Example 1: Character Encoding Declaration 

<head>
    <title>Document with Encoding</title>

    <!-- Traditional encoding declaration -->
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />

    <!-- Modern equivalent (preferred) -->
    <meta charset="UTF-8" />
</head>

Example 2: Content Type with Language 

<head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <meta http-equiv="Content-Language" content="en-US" />

    <title>English Language Document</title>
</head>

Example 3: Multiple Meta Directives 

<head>
    <title>Complete Metadata Example</title>

    <!-- Character encoding -->
    <meta charset="UTF-8" />

    <!-- HTTP equivalent directives -->
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <meta http-equiv="Content-Language" content="en" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />

    <!-- Standard metadata -->
    <meta name="author" content="John Doe" />
    <meta name="description" content="Sample document" />
</head>

Example 4: Legacy Web Page Conversion 

<!-- Original web page headers -->
<head>
    <title>Legacy Web Page</title>

    <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" />
    <meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7" />
    <meta http-equiv="imagetoolbar" content="no" />

    <!-- When converted to PDF, these are preserved but not processed -->
</head>

Example 5: Multi-Language Document 

<head>
    <title>Bilingual Document</title>

    <meta charset="UTF-8" />
    <meta http-equiv="Content-Language" content="en-US, es-MX" />

    <meta name="description" content="English and Spanish content" />
</head>

Example 6: Data-Bound Encoding 

<!-- Model: { encoding: "UTF-8", contentType: "text/html" } -->

<head>
    <title>Dynamic Metadata</title>

    <meta http-equiv="Content-Type"
          content="; charset=" />
</head>

Example 7: Complete Document Headers 

<head>
    <title>Professional Report</title>

    <!-- Character encoding -->
    <meta charset="UTF-8" />

    <!-- HTTP equivalents (informational in PDF) -->
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <meta http-equiv="Content-Language" content="en-US" />

    <!-- Standard metadata -->
    <meta name="author" content="Corporate Team" />
    <meta name="description" content="Annual corporate report" />
    <meta name="keywords" content="report, finance, annual" />

    <!-- Open Graph metadata -->
    <meta property="og:title" content="Annual Report 2024" />
    <meta property="og:type" content="document" />
</head>

Example 8: Browser Compatibility Headers (Preserved) 

<head>
    <title>Cross-Browser Document</title>

    <!-- These are preserved when converting HTML to PDF -->
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta http-equiv="cleartype" content="on" />

    <meta charset="UTF-8" />
</head>

Example 9: Content Security Policy (Informational) 

<head>
    <title>Secure Document</title>

    <!-- CSP directive (not enforced in PDF, but preserved) -->
    <meta http-equiv="Content-Security-Policy"
          content="default-src 'self'; script-src 'none';" />

    <meta charset="UTF-8" />
</head>

Example 10: Conditional Encoding 

<!-- Model: { useUnicode: true } -->

<head>
    <title>Conditional Encoding Document</title>

    <meta http-equiv="Content-Type"
          content="text/html; charset=" />
</head>

Example 11: International Character Set 

<head>
    <title>国际文档</title> <!-- International Document -->

    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <meta http-equiv="Content-Language" content="zh-CN" />

    <meta name="description" content="Chinese language document" />
</head>

Example 12: Technical Documentation 

<head>
    <title>API Documentation</title>

    <meta charset="UTF-8" />
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <meta http-equiv="Content-Language" content="en" />

    <meta name="author" content="Development Team" />
    <meta name="description" content="Complete API reference documentation" />
</head>

Example 13: Archive Document 

<head>
    <title>Historical Archive Document</title>

    <!-- Preserve original encoding declaration -->
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <meta http-equiv="Content-Language" content="en-GB" />

    <!-- Document archive metadata -->
    <meta name="archive-date" content="2024-01-15" />
    <meta name="original-url" content="https://example.com/original" />
</head>

Example 14: Form Document 

<head>
    <title>Application Form</title>

    <meta charset="UTF-8" />
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />

    <meta name="author" content="HR Department" />
    <meta name="description" content="Employee application form" />
</head>
<body>
    <form id="applicationForm">
        <!-- Form content -->
    </form>
</body>

Example 15: Web-to-PDF with All Meta Tags 

<head>
    <title>Complete Web Page - Converted to PDF</title>

    <!-- Character encoding -->
    <meta charset="UTF-8" />
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />

    <!-- Browser compatibility -->
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />

    <!-- Language -->
    <meta http-equiv="Content-Language" content="en-US" />

    <!-- Standard metadata -->
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta name="author" content="Web Development Team" />
    <meta name="description" content="Complete web page example" />
    <meta name="keywords" content="web, HTML, PDF" />

    <!-- Open Graph -->
    <meta property="og:title" content="Complete Web Page" />
    <meta property="og:type" content="website" />
    <meta property="og:description" content="Example of complete web page metadata" />
</head>

See Also