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");

IRON VB CONVERTER ERROR developers@ironsoftware.com

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");

IRON VB CONVERTER ERROR developers@ironsoftware.com

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

IRON VB CONVERTER ERROR developers@ironsoftware.com

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

IRON VB CONVERTER ERROR developers@ironsoftware.com

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");

IRON VB CONVERTER ERROR developers@ironsoftware.com

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;

IRON VB CONVERTER ERROR developers@ironsoftware.com

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

IRON VB CONVERTER ERROR developers@ironsoftware.com

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");
}

IRON VB CONVERTER ERROR developers@ironsoftware.com

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");

IRON VB CONVERTER ERROR developers@ironsoftware.com

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");
    }
}

IRON VB CONVERTER ERROR developers@ironsoftware.com

• 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");

IRON VB CONVERTER ERROR developers@ironsoftware.com

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");

IRON VB CONVERTER ERROR developers@ironsoftware.com

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

Quick Decision Matrix: IronPDF versus Other .NET PDF Converters

请注意： 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

真实环境下的 HTML 转 PDF 比较：渲染 Reddit 主页

为了评估输出 PDF 的质量，我们测试了包含动态网络内容、现代 CSS 和 JavaScript HTML 元素的 Reddit 主页。 该页面是生成输出 PDF 的理想测试案例。

https://www.reddit.com/

IronPDF

IronPDF 提供像素级精确的结果，保留所有动态网页内容、现代的网页字体样式和交互元素，完全按照 Chrome 中显示，只需要几行代码。

Syncfusion

Syncfusion 渲染的 PDF 大多数内容和样式都缺失，特别是动态内容。 最初被 Reddit 的安全措施阻挡。 要达到更好的结果需要大量命令行调试，然而输出仍然是不完整的。

Aspose.PDF

Aspose.PDF 首先需要手动下载 HTML（不支持直接 URL）。 转换后，输出缺乏适当的格式，几乎所有内容部分都缺失，使其不适合处理包含动态内容的现代网页。

wkhtmltopdf

wkhtmltopdf 完成速度较快但生成了一个平凡、静态的页面，缺少关键内容如实时更新、动态元素和交互部分。 这展示了 wkhtmltopdf 不适用于现代的、JavaScript 驱动的网站。

性能和输出 PDF 质量的结论

对于需要可靠的 HTML 转 PDF 转换器的 .NET 开发者来说，IronPDF 以最少的代码量、易于使用的 API 和频繁的产品增强而脱颖而出。

在涉及 Web 内容的真实世界测试中，它提供了最快速、最精确的结果，而 Syncfusion 表现落后，Aspose 需要额外步骤，而 wkhtmltopdf 缺失现代样式。 IronPDF 为现代 HTML 转 PDF 转换工作流提供了速度、精确性和简便性的最佳平衡。

请注意： Aspose、SyncFusion 和 wkhtmltopdf 是其各自所有者的商标。 本网站与它们无关且未得到它们的认可。 所有名称、徽标和品牌属于其所有者，并且比较基于撰写时公开可用的信息。

摘要

本指南涵盖了在 .NET 中将 HTML 转换为 PDF 所需的一切：从基本字符串转换到异步处理、数字签名和批量生成等高级功能。 我们展示了三种转换方法、基本配置、高级功能和安全设置，并通过动态文档生成的实际测试比较了 IronPDF 和其他库的表现。

而竞争对手在现代网站上表现不佳或者需要复杂的解决办法，IronPDF 的强大渲染引擎以最少的代码量提供了完美的结果。

准备好简化您的 PDF 工作流并在几行代码内体验多功能的 PDF 生成吗？ 通过 NuGet 包管理器（或选择在 Visual Studio 中管理 NuGet 包）安装 IronPDF 并立即将您的第一个 HTML 转换为 PDF。

启动您的 30 天免费试用进行无水印的生产测试。 灵活的许可方案从 $799 开始，提供透明的团队定价以满足您的需求。

查看 IronPDF 授权信息

快速解决常见错误

• 首次渲染慢？ 正常。 Chrome 在 2–3 秒内初始化，然后加速。
• 云问题？ 至少使用 Azure B1 或同等资源。
• 资产丢失？ 设置基本路径或嵌入为 base64。
• 元素丢失？ 为 JavaScript 执行添加 RenderDelay。
• 渲染时的内存问题？ 更新到 v2025.9.4 以解决 HTML 转 PDF、戳记和页眉/页脚问题。
• 表单字段问题（如长文本区、复选框）？ 在 v2025.7.17 中已修复； 确保复选框具有唯一名称。
• 自定义页眉/页脚裁剪或特殊字符损坏？ 在 v2025.8.8 中已解决； 测试自动换行和元数据。

从 IronPDF 的工程师团队获得帮助，全天候提供服务

• 综合排查指南
• 性能优化策略
• 工程支持请求
• 快速排查清单