Convert HTML to PDF in C# - Complete .NET Developer Guide

How to Convert HTML String to PDF

The most fundamental operation is HTML string to PDF. This method is perfect for dynamically generated HTML content. The RenderHtmlAsPdf method fully supports HTML5, CSS3, JavaScript, and images when you convert HTML to PDF directly.

using IronPdf;

// Create the Chrome renderer
var renderer = new ChromePdfRenderer();

// Convert HTML string to PDF
var pdf = renderer.RenderHtmlAsPdf("<h1>Hello IronPdf</h1>");

// Save the PDF
pdf.SaveAs("output.pdf");

using IronPdf;

// Create the Chrome renderer
var renderer = new ChromePdfRenderer();

// Convert HTML string to PDF
var pdf = renderer.RenderHtmlAsPdf("<h1>Hello IronPdf</h1>");

// Save the PDF
pdf.SaveAs("output.pdf");

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When your HTML string references local assets like images or stylesheets, use the BaseUrlPath parameter to properly convert HTML content with all resources:

using IronPdf;

var renderer = new ChromePdfRenderer();

// Convert HTML content with local image and CSS references
string html = @"
    <link rel='stylesheet' href='styles.css'>
    <img src='logo.png' alt='Company Logo'>
    <h1>Company Report</h1>
    <p>Annual report content...</p>";

// Set base path for resolving relative URLs in HTML to PDF conversion
var pdf = renderer.RenderHtmlAsPdf(html, @"C:\MyProject\Assets\");
pdf.SaveAs("report.pdf");

using IronPdf;

var renderer = new ChromePdfRenderer();

// Convert HTML content with local image and CSS references
string html = @"
    <link rel='stylesheet' href='styles.css'>
    <img src='logo.png' alt='Company Logo'>
    <h1>Company Report</h1>
    <p>Annual report content...</p>";

// Set base path for resolving relative URLs in HTML to PDF conversion
var pdf = renderer.RenderHtmlAsPdf(html, @"C:\MyProject\Assets\");
pdf.SaveAs("report.pdf");

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RELATED HOW-TO ARTICLE: How to Convert HTML String to PDF in C#

How to Export Existing URL to PDF

Rendering entire web pages to PDFs with C# enables teams to separate PDF design and back-end rendering work. This approach lets you convert any specified URL directly to PDF format.

Print vs Screen CSS

You can configure IronPDF to render using either CSS media type.

using IronPdf;
using IronPdf.Rendering;

// Initialize HTML to PDF converter
var renderer = new ChromePdfRenderer();

// Configure CSS media type for rendering specified URLs
renderer.RenderingOptions.CssMediaType = PdfCssMediaType.Print;

// Screen media type shows the entire web page as displayed on screen

using IronPdf;
using IronPdf.Rendering;

// Initialize HTML to PDF converter
var renderer = new ChromePdfRenderer();

// Configure CSS media type for rendering specified URLs
renderer.RenderingOptions.CssMediaType = PdfCssMediaType.Print;

// Screen media type shows the entire web page as displayed on screen

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JavaScript Support

IronPDF fully supports JavaScript, jQuery, and even AJAX when you convert HTML to PDF. For dynamic HTML content, you can configure IronPDF to wait for JavaScript completion before rendering web pages into PDF. This is perfect for single-page applications and dynamic websites.

using IronPdf;

// Configure JavaScript rendering for dynamic HTML content to PDF
var renderer = new ChromePdfRenderer();

// Enable JavaScript execution during PDF generation
renderer.RenderingOptions.EnableJavaScript = true;

// WaitFor.RenderDelay pauses before capturing the HTML
renderer.RenderingOptions.WaitFor.RenderDelay = 500; // milliseconds

using IronPdf;

// Configure JavaScript rendering for dynamic HTML content to PDF
var renderer = new ChromePdfRenderer();

// Enable JavaScript execution during PDF generation
renderer.RenderingOptions.EnableJavaScript = true;

// WaitFor.RenderDelay pauses before capturing the HTML
renderer.RenderingOptions.WaitFor.RenderDelay = 500; // milliseconds

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JavaScript execution can also be shown when rendering an advanced d3.js chord chart from a web page to PDF format:

using IronPdf;

// Create renderer for JavaScript-heavy HTML
var renderer = new ChromePdfRenderer();

// Convert d3.js visualization web page to PDF
var pdf = renderer.RenderUrlAsPdf("https://bl.ocks.org/mbostock/4062006");

// Save the interactive chart as static PDF
pdf.SaveAs("chart.pdf");

using IronPdf;

// Create renderer for JavaScript-heavy HTML
var renderer = new ChromePdfRenderer();

// Convert d3.js visualization web page to PDF
var pdf = renderer.RenderUrlAsPdf("https://bl.ocks.org/mbostock/4062006");

// Save the interactive chart as static PDF
pdf.SaveAs("chart.pdf");

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Responsive CSS

As responsive web pages are designed to be viewed in a browser, and IronPDF does not open a real browser window in your server's OS, responsive HTML elements may render at their smallest size. PdfCssMediaType.Print is recommended to navigate this issue when rendering entire web pages.

// Configure for optimal responsive design handling in HTML to PDF

renderer.RenderingOptions.CssMediaType = IronPdf.Rendering.PdfCssMediaType.Print;

// Configure for optimal responsive design handling in HTML to PDF

renderer.RenderingOptions.CssMediaType = IronPdf.Rendering.PdfCssMediaType.Print;

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RELATED HOW-TO ARTICLE: How to Render URL to PDF

How to Convert HTML File to PDF

Converting local HTML files to PDF preserves all relative assets including CSS, images, and JavaScript, as if opened using the file:// protocol. This HTML to PDF method is best for converting templates or pre-designed HTML pages to PDF documents.

using IronPdf;

// Initialize ChromePdfRenderer for HTML file conversion
var renderer = new ChromePdfRenderer();

// Convert HTML file to PDF documents
// Preserves all relative paths and linked resources in HTML
var pdf = renderer.RenderHtmlFileAsPdf("Assets/TestInvoice1.html");

// Save the HTML file as PDF 
pdf.SaveAs("Invoice.pdf");

// All CSS, JavaScript, and images load correctly in the generated PDF

using IronPdf;

// Initialize ChromePdfRenderer for HTML file conversion
var renderer = new ChromePdfRenderer();

// Convert HTML file to PDF documents
// Preserves all relative paths and linked resources in HTML
var pdf = renderer.RenderHtmlFileAsPdf("Assets/TestInvoice1.html");

// Save the HTML file as PDF 
pdf.SaveAs("Invoice.pdf");

// All CSS, JavaScript, and images load correctly in the generated PDF

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RELATED HOW-TO ARTICLE: Render HTML File to PDF

How to Generate HTML Template for Batch PDF Creation

Basic Batch PDF Creation

Batch PDF creation is essential for generating multiple personalized PDF documents efficiently. For basic scenarios, the String.Format method in C# works best for simple PDF manipulation.

// Simple HTML templating with String.Format
string htmlTemplate = String.Format("<h1>Hello {0}!</h1>", "World");

// Results in HTML content: <h1>Hello World!</h1>

// Simple HTML templating with String.Format
string htmlTemplate = String.Format("<h1>Hello {0}!</h1>", "World");

// Results in HTML content: <h1>Hello World!</h1>

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For longer templates when you need to generate PDF documents, use placeholder replacement in your HTML content: using IronPdf;

// Define reusable HTML template for PDF files
var htmlTemplate = "<p>Dear [[NAME]],</p><p>Thank you for your order.</p>";

// Customer names for batch PDF conversion processing
var names = new[] { "John", "James", "Jenny" };

// Create personalized PDF documents for each customer
var renderer = new ChromePdfRenderer();

foreach (var name in names)
{
    // Replace placeholder with actual data in HTML string
    var htmlInstance = htmlTemplate.Replace("[[NAME]]", name);

    // Generate personalized PDF document from HTML content
    var pdf = renderer.RenderHtmlAsPdf(htmlInstance);

    // Save with customer-specific filename as PDF files
    pdf.SaveAs($"{name}-invoice.pdf");
}

// Define reusable HTML template for PDF files
var htmlTemplate = "<p>Dear [[NAME]],</p><p>Thank you for your order.</p>";

// Customer names for batch PDF conversion processing
var names = new[] { "John", "James", "Jenny" };

// Create personalized PDF documents for each customer
var renderer = new ChromePdfRenderer();

foreach (var name in names)
{
    // Replace placeholder with actual data in HTML string
    var htmlInstance = htmlTemplate.Replace("[[NAME]]", name);

    // Generate personalized PDF document from HTML content
    var pdf = renderer.RenderHtmlAsPdf(htmlInstance);

    // Save with customer-specific filename as PDF files
    pdf.SaveAs($"{name}-invoice.pdf");
}

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HTML to PDF Templating with Handlebars.NET

For complex templates with loops and conditionals when you convert HTML to PDF, use advanced templating with Handlebars.NET to generate PDF documents with dynamic HTML content.

# First, install Handlebars.NET for HTML to PDF templating
PM > Install-Package Handlebars.NET

# First, install Handlebars.NET for HTML to PDF templating
PM > Install-Package Handlebars.NET

using HandlebarsDotNet;
using IronPdf;

// Define Handlebars template with placeholders for HTML content
var source = 
    @"<div class=""entry"">
        <h1>{{title}}</h1>
        <div class=""body"">
            {{body}}
        </div>
    </div>";

// Compile template for reuse in PDF conversion
var template = Handlebars.Compile(source);

// Create data object (can be database records) for HTML to PDF directly
var data = new { 
    title = "Monthly Report", 
    body = "Sales increased by 15% this month." 
};

// Merge template with data to create HTML content
var htmlResult = template(data);

// Convert templated HTML to PDF using the PDF converter
var renderer = new ChromePdfRenderer();
var pdf = renderer.RenderHtmlAsPdf(htmlResult);

pdf.SaveAs("monthly-report.pdf");

using HandlebarsDotNet;
using IronPdf;

// Define Handlebars template with placeholders for HTML content
var source = 
    @"<div class=""entry"">
        <h1>{{title}}</h1>
        <div class=""body"">
            {{body}}
        </div>
    </div>";

// Compile template for reuse in PDF conversion
var template = Handlebars.Compile(source);

// Create data object (can be database records) for HTML to PDF directly
var data = new { 
    title = "Monthly Report", 
    body = "Sales increased by 15% this month." 
};

// Merge template with data to create HTML content
var htmlResult = template(data);

// Convert templated HTML to PDF using the PDF converter
var renderer = new ChromePdfRenderer();
var pdf = renderer.RenderHtmlAsPdf(htmlResult);

pdf.SaveAs("monthly-report.pdf");

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RELATED HOW-TO ARTICLE: Learn more about Handlebars.NET on GitHub

<!DOCTYPE html>
<html>
  <head>
    <style type="text/css" media="print">
      .page {
        page-break-after: always;
        page-break-inside: avoid;
      }
    </style>
  </head>
  <body>
    <div class="page">
      <h1>Page 1 Content</h1>
    </div>
    <div class="page">
      <h1>Page 2 Content</h1>
    </div>
    <div class="page">
      <h1>Page 3 Content</h1>
    </div>
  </body>
</html>

<!DOCTYPE html>
<html>
  <head>
    <style type="text/css" media="print">
      .page {
        page-break-after: always;
        page-break-inside: avoid;
      }
    </style>
  </head>
  <body>
    <div class="page">
      <h1>Page 1 Content</h1>
    </div>
    <div class="page">
      <h1>Page 2 Content</h1>
    </div>
    <div class="page">
      <h1>Page 3 Content</h1>
    </div>
  </body>
</html>

How to Generate PDF Using Async Method

IronPDF delivers enterprise-grade performance with full async and multithreading support for your HTML to PDF conversion requirements when you need to generate PDF files at scale.

using IronPdf;
using System.Threading.Tasks;

// Async method for non-blocking PDF generation from HTML content
public async Task<byte[]> GeneratePdfAsync(string html)
{
    var renderer = new ChromePdfRenderer();

    // Async HTML to PDF conversion preserves thread pool
    var pdf = await renderer.RenderHtmlAsPdfAsync(html);

    // Return PDF files as byte array for web responses
    return pdf.BinaryData;
}

// Concurrent batch PDF generation for multiple HTML strings
public async Task GenerateMultiplePdfsAsync(List<string> htmlTemplates)
{
    var renderer = new ChromePdfRenderer();

    // Create parallel conversion tasks to generate PDF documents
    var tasks = htmlTemplates.Select(html => 
        renderer.RenderHtmlAsPdfAsync(html)
    );

    // Await all PDF conversions simultaneously
    var pdfs = await Task.WhenAll(tasks);

    // Save generated PDF files from HTML content
    for (int i = 0; i < pdfs.Length; i++)
    {
        pdfs[i].SaveAs($"document-{i}.pdf");
    }
}

using IronPdf;
using System.Threading.Tasks;

// Async method for non-blocking PDF generation from HTML content
public async Task<byte[]> GeneratePdfAsync(string html)
{
    var renderer = new ChromePdfRenderer();

    // Async HTML to PDF conversion preserves thread pool
    var pdf = await renderer.RenderHtmlAsPdfAsync(html);

    // Return PDF files as byte array for web responses
    return pdf.BinaryData;
}

// Concurrent batch PDF generation for multiple HTML strings
public async Task GenerateMultiplePdfsAsync(List<string> htmlTemplates)
{
    var renderer = new ChromePdfRenderer();

    // Create parallel conversion tasks to generate PDF documents
    var tasks = htmlTemplates.Select(html => 
        renderer.RenderHtmlAsPdfAsync(html)
    );

    // Await all PDF conversions simultaneously
    var pdfs = await Task.WhenAll(tasks);

    // Save generated PDF files from HTML content
    for (int i = 0; i < pdfs.Length; i++)
    {
        pdfs[i].SaveAs($"document-{i}.pdf");
    }
}

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• Use 64-bit systems for optimal PDF generation performance.
• Ensure adequate server resources when you generate PDF documents (avoid underpowered free tiers)
• Allow sufficient RenderDelay for complex JavaScript in HTML content.
• Reuse ChromePdfRenderer instances when possible.
• Leverage v2025.9.4 memory fixes for batch/async ops to reduce resource usage; test for reduced file sizes with repeated custom headers/footers.

RELATED HOW-TO ARTICLE: How to Generate PDFs with Async and Multithreading

How to Add Advanced Security Features

How to Add Password Protect for PDF Files in .NET

Secure sensitive generated PDF documents with passwords and permissions when you convert HTML content to protected PDF format.

using IronPdf;
var renderer = new ChromePdfRenderer();

// Convert HTML to PDF with security
var pdf = renderer.RenderHtmlAsPdf("<h1>Confidential Report</h1>");

// Configure security settings for PDF files
pdf.SecuritySettings.UserPassword = "user123";     // Password to open PDF documents
pdf.SecuritySettings.OwnerPassword = "owner456";   // Password to modify PDF files

// Set granular permissions for PDF format
pdf.SecuritySettings.AllowUserCopyPasteContent = false;
pdf.SecuritySettings.AllowUserAnnotations = false;
pdf.SecuritySettings.AllowUserPrinting = PrintPermissions.LowQualityPrint;

// Apply strong encryption to PDF documents
pdf.SecuritySettings.EncryptionAlgorithm = PdfEncryptionAlgorithm.AES256;
pdf.SaveAs("secure-document.pdf");

using IronPdf;
var renderer = new ChromePdfRenderer();

// Convert HTML to PDF with security
var pdf = renderer.RenderHtmlAsPdf("<h1>Confidential Report</h1>");

// Configure security settings for PDF files
pdf.SecuritySettings.UserPassword = "user123";     // Password to open PDF documents
pdf.SecuritySettings.OwnerPassword = "owner456";   // Password to modify PDF files

// Set granular permissions for PDF format
pdf.SecuritySettings.AllowUserCopyPasteContent = false;
pdf.SecuritySettings.AllowUserAnnotations = false;
pdf.SecuritySettings.AllowUserPrinting = PrintPermissions.LowQualityPrint;

// Apply strong encryption to PDF documents
pdf.SecuritySettings.EncryptionAlgorithm = PdfEncryptionAlgorithm.AES256;
pdf.SaveAs("secure-document.pdf");

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How to Add Digital Signatures to PDF Files

Add cryptographic signatures to ensure PDF document authenticity when you generate PDF files from HTML content.

using IronPdf;
using IronPdf.Signing;

var renderer = new ChromePdfRenderer();

// Generate PDF from HTML page
var pdf = renderer.RenderHtmlAsPdf("<h1>Contract Agreement</h1>");

// Create digital signature with certificate for PDF files
var signature = new PdfSignature("certificate.pfx", "password")
{
    SigningContact = "legal@company.com",
    SigningLocation = "New York, NY",
    SigningReason = "Contract Approval",
    SignerName = "Authorized Signer"  // New property in v2025.8.8 for enhanced signature details
};

// Apply signature to PDF documents
pdf.Sign(signature);
pdf.SaveAs("signed-contract.pdf");

using IronPdf;
using IronPdf.Signing;

var renderer = new ChromePdfRenderer();

// Generate PDF from HTML page
var pdf = renderer.RenderHtmlAsPdf("<h1>Contract Agreement</h1>");

// Create digital signature with certificate for PDF files
var signature = new PdfSignature("certificate.pfx", "password")
{
    SigningContact = "legal@company.com",
    SigningLocation = "New York, NY",
    SigningReason = "Contract Approval",
    SignerName = "Authorized Signer"  // New property in v2025.8.8 for enhanced signature details
};

// Apply signature to PDF documents
pdf.Sign(signature);
pdf.SaveAs("signed-contract.pdf");

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RELATED HOW-TO ARTICLE: Digitally Signing PDF Documents with C#

Quick Decision Matrix: IronPDF versus Other .NET PDF Converters

Please note: Solutions like PDFSharp and iTextSharp lack native HTML to PDF conversion capabilities and were excluded from this comparison. QuestPDF requires a code-first approach with no HTML support. Developers using these libraries must rely on third-party tools for HTML rendering.

RELATED COMPARISONS:

• Compare IronPDF and Syncfusion
• Compare IronPDF and Aspose

Detailed Comparison: IronPDF versus Other .NET PDF Converters

Real-life HTML to PDF Conversion Comparison: Rendering Reddit's Homepage

To evaluate the output PDF quality, we tested these libraries with Reddit's homepage containing dynamic web content, modern CSS, and JavaScript HTML elements. This page serves as an ideal test case for output PDF generation.

https://www.reddit.com/

IronPDF

IronPDF delivers pixel-perfect results, preserving all dynamic web content, modern web fonts styling, and interactive elements exactly as displayed in Chrome, all in just a few lines of code.

Syncfusion

Syncfusion rendered PDF with most sections and styling missing, especially dynamic content. Initially blocked by Reddit's security. Achieving better results requires extensive command-line tuning, yet output remains incomplete.

Aspose.PDF

Aspose.PDF required manual HTML download first (no direct URL support). After conversion, output lacked proper formatting and missed nearly all content sections, making it unsuitable for modern web with dynamic content.

wkhtmltopdf

wkhtmltopdf completed quickly but produced a plain, static page missing critical content like live updates, dynamic elements, and interactive sections. This demonstrates wkhtmltopdf's incompatibility with modern, JavaScript-driven websites.

Conclusion on Performance and Output PDF Quality

For .NET developers needing a reliable HTML to PDF converter, IronPDF stands out with minimal code, easy-to-use APIs, and frequent product enhancements.

In a real-world test on web content, it delivered the fastest, most accurate results while Syncfusion lagged behind, Aspose required extra steps, and wkhtmltopdf missed modern styling. IronPDF offers the best balance of speed, accuracy, and simplicity for today’s HTML to PDF conversion workflows.

Please note: Aspose, SyncFusion, and wkhtmltopdf are trademarks of their respective owners. This site is not affiliated with or endorsed by them. All names, logos, and brands belong to their owners, and comparisons are based on publicly available information at the time of writing.

Summary

This guide covered everything needed to convert HTML to PDF in .NET: from basic string conversion to advanced features like async processing, digital signatures, and batch generation. We demonstrated three conversion methods, essential configurations, advanced features and security settings, and compared IronPDF with other libraries through real-world testing of dynamic document generation.

While competitors struggled with modern websites or required complex workarounds, IronPDF delivered flawless results with minimal code and powerful rendering engine.

Ready to streamline your PDF workflow and experience versatile PDF generation in just a few lines of code? Install IronPDF through NuGet Package Manager (or select Manage NuGet Package in Visual Studio) and convert your first HTML to PDF today.

Start your free 30-day trial for production testing without watermarks. Flexible licensing starts at $799 with transparent team pricing that scales with your needs.

View IronPDF Licensing

Quick Fixes on Common Errors

• Slow first render? Normal. Chrome initializes in 2–3s, then speeds up.
• Cloud issues? Use at least Azure B1 or equivalent resources.
• Missing assets? Set base paths or embed as base64.
• Missing elements? Add RenderDelay for JavaScript execution.
• Memory in rendering? Update to v2025.9.4 for fixes in HTML to PDF, stamps, and headers/footers.
• Form field issues (e.g., long textareas, checkboxes)? Fixed in v2025.7.17; ensure unique names for checkboxes.
• Custom header/footer clipping or special characters corrupted? Resolved in v2025.8.8; test word-wrapping and metadata.

Get Help From The Engineers Who Built IronPDF, 24/7

• Comprehensive troubleshooting guide
• Performance optimization strategies
• Engineering support requests
• Quick troubleshooting checklist