How to Migrate from wkhtmltopdf to IronPDF in C#

How the SSRF Attack Works

The Server-Side Request Forgery vulnerability allows attackers to access internal services, steal credentials, scan your internal network, and exfiltrate sensitive data through crafted HTML:

<iframe src="http://169.254.169.254/latest/meta-data/iam/security-credentials/"></iframe>
<img src="http://internal-database:5432/admin"/>

<iframe src="http://169.254.169.254/latest/meta-data/iam/security-credentials/"></iframe>
<img src="http://internal-database:5432/admin"/>

When wkhtmltopdf renders this HTML, it fetches these URLs from your server's network context, bypassing firewalls and security controls.

Affected Wrapper Libraries

All .NET wrappers for wkhtmltopdf inherit these vulnerabilities:

If you use any of these libraries, you are vulnerable to CVE-2022-35583.

Step 1: Remove wkhtmltopdf Packages and Binaries

Remove all wkhtmltopdf wrapper packages:

# Remove wkhtmltopdf wrapper (whichever you're using)
dotnet remove package WkHtmlToPdf-DotNet
dotnet remove package DinkToPdf
dotnet remove package TuesPechkin
dotnet remove package Rotativa
dotnet remove package Rotativa.AspNetCore
dotnet remove package NReco.PdfGenerator

# Remove wkhtmltopdf binary from your deployment
# Delete wkhtmltopdf.exe, wkhtmltox.dll, etc.

# Remove wkhtmltopdf wrapper (whichever you're using)
dotnet remove package WkHtmlToPdf-DotNet
dotnet remove package DinkToPdf
dotnet remove package TuesPechkin
dotnet remove package Rotativa
dotnet remove package Rotativa.AspNetCore
dotnet remove package NReco.PdfGenerator

# Remove wkhtmltopdf binary from your deployment
# Delete wkhtmltopdf.exe, wkhtmltox.dll, etc.

Step 2: Install IronPDF

# Add IronPDF (secure, modern alternative)
dotnet add package IronPdf

# Add IronPDF (secure, modern alternative)
dotnet add package IronPdf

Step 3: Update Namespaces

Replace wkhtmltopdf namespaces with the IronPdf namespace:

// Before (wkhtmltopdf)
using WkHtmlToPdfDotNet;
using WkHtmlToPdfDotNet.Contracts;

// After (IronPDF)
using IronPdf;

// Before (wkhtmltopdf)
using WkHtmlToPdfDotNet;
using WkHtmlToPdfDotNet.Contracts;

// After (IronPDF)
using IronPdf;

Step 4: Initialize License

Add license initialization at application startup:

IronPdf.License.LicenseKey = "YOUR-LICENSE-KEY";

IronPdf.License.LicenseKey = "YOUR-LICENSE-KEY";

Converting HTML to PDF

The most fundamental operation reveals the complexity difference between these .NET PDF approaches.

wkhtmltopdf Approach:

// NuGet: Install-Package WkHtmlToPdf-DotNet
using WkHtmlToPdfDotNet;
using WkHtmlToPdfDotNet.Contracts;
using System.IO;

class Program
{
    static void Main()
    {
        var converter = new SynchronizedConverter(new PdfTools());
        var doc = new HtmlToPdfDocument()
        {
            GlobalSettings = {
                ColorMode = ColorMode.Color,
                Orientation = Orientation.Portrait,
                PaperSize = PaperKind.A4
            },
            Objects = {
                new ObjectSettings()
                {
                    HtmlContent = "<h1>Hello World</h1><p>This is a PDF from HTML.</p>"
                }
            }
        };
        byte[] pdf = converter.Convert(doc);
        File.WriteAllBytes("output.pdf", pdf);
    }
}

// NuGet: Install-Package WkHtmlToPdf-DotNet
using WkHtmlToPdfDotNet;
using WkHtmlToPdfDotNet.Contracts;
using System.IO;

class Program
{
    static void Main()
    {
        var converter = new SynchronizedConverter(new PdfTools());
        var doc = new HtmlToPdfDocument()
        {
            GlobalSettings = {
                ColorMode = ColorMode.Color,
                Orientation = Orientation.Portrait,
                PaperSize = PaperKind.A4
            },
            Objects = {
                new ObjectSettings()
                {
                    HtmlContent = "<h1>Hello World</h1><p>This is a PDF from HTML.</p>"
                }
            }
        };
        byte[] pdf = converter.Convert(doc);
        File.WriteAllBytes("output.pdf", pdf);
    }
}

IronPDF Approach:

// NuGet: Install-Package IronPdf
using IronPdf;
using System;

class Program
{
    static void Main()
    {
        var renderer = new ChromePdfRenderer();
        var pdf = renderer.RenderHtmlAsPdf("<h1>Hello World</h1><p>This is a PDF from HTML.</p>");
        pdf.SaveAs("output.pdf");
    }
}

// NuGet: Install-Package IronPdf
using IronPdf;
using System;

class Program
{
    static void Main()
    {
        var renderer = new ChromePdfRenderer();
        var pdf = renderer.RenderHtmlAsPdf("<h1>Hello World</h1><p>This is a PDF from HTML.</p>");
        pdf.SaveAs("output.pdf");
    }
}

wkhtmltopdf requires creating a SynchronizedConverter with PdfTools, constructing an HtmlToPdfDocument with GlobalSettings and Objects, setting properties like ColorMode, Orientation, and PaperSize, calling converter.Convert() to get raw bytes, and manually writing to a file with File.WriteAllBytes().

IronPDF eliminates this ceremony entirely—create a ChromePdfRenderer, call RenderHtmlAsPdf(), and use the built-in SaveAs() method.

For advanced HTML-to-PDF scenarios, see the HTML to PDF conversion guide.

Converting URLs to PDF

URL-to-PDF conversion shows similar complexity patterns.

wkhtmltopdf Approach:

// NuGet: Install-Package WkHtmlToPdf-DotNet
using WkHtmlToPdfDotNet;
using WkHtmlToPdfDotNet.Contracts;
using System.IO;

class Program
{
    static void Main()
    {
        var converter = new SynchronizedConverter(new PdfTools());
        var doc = new HtmlToPdfDocument()
        {
            GlobalSettings = {
                ColorMode = ColorMode.Color,
                Orientation = Orientation.Portrait,
                PaperSize = PaperKind.A4
            },
            Objects = {
                new ObjectSettings()
                {
                    Page = "https://www.example.com"
                }
            }
        };
        byte[] pdf = converter.Convert(doc);
        File.WriteAllBytes("webpage.pdf", pdf);
    }
}

// NuGet: Install-Package WkHtmlToPdf-DotNet
using WkHtmlToPdfDotNet;
using WkHtmlToPdfDotNet.Contracts;
using System.IO;

class Program
{
    static void Main()
    {
        var converter = new SynchronizedConverter(new PdfTools());
        var doc = new HtmlToPdfDocument()
        {
            GlobalSettings = {
                ColorMode = ColorMode.Color,
                Orientation = Orientation.Portrait,
                PaperSize = PaperKind.A4
            },
            Objects = {
                new ObjectSettings()
                {
                    Page = "https://www.example.com"
                }
            }
        };
        byte[] pdf = converter.Convert(doc);
        File.WriteAllBytes("webpage.pdf", pdf);
    }
}

IronPDF Approach:

// NuGet: Install-Package IronPdf
using IronPdf;
using System;

class Program
{
    static void Main()
    {
        var renderer = new ChromePdfRenderer();
        var pdf = renderer.RenderUrlAsPdf("https://www.example.com");
        pdf.SaveAs("webpage.pdf");
    }
}

// NuGet: Install-Package IronPdf
using IronPdf;
using System;

class Program
{
    static void Main()
    {
        var renderer = new ChromePdfRenderer();
        var pdf = renderer.RenderUrlAsPdf("https://www.example.com");
        pdf.SaveAs("webpage.pdf");
    }
}

wkhtmltopdf uses the Page property in ObjectSettings to specify a URL, requiring the same document construction pattern. IronPDF provides a dedicated RenderUrlAsPdf() method that clearly expresses intent.

Explore the URL to PDF documentation for authentication and custom header options.

Custom Settings: HTML Files with Page Configuration

Configuring orientation, margins, and paper size requires different approaches.

wkhtmltopdf Approach:

// NuGet: Install-Package WkHtmlToPdf-DotNet
using WkHtmlToPdfDotNet;
using WkHtmlToPdfDotNet.Contracts;
using System.IO;

class Program
{
    static void Main()
    {
        var converter = new SynchronizedConverter(new PdfTools());
        var doc = new HtmlToPdfDocument()
        {
            GlobalSettings = {
                ColorMode = ColorMode.Color,
                Orientation = Orientation.Landscape,
                PaperSize = PaperKind.A4,
                Margins = new MarginSettings() { Top = 10, Bottom = 10, Left = 10, Right = 10 }
            },
            Objects = {
                new ObjectSettings()
                {
                    Page = "input.html",
                    WebSettings = { DefaultEncoding = "utf-8" }
                }
            }
        };
        byte[] pdf = converter.Convert(doc);
        File.WriteAllBytes("custom-output.pdf", pdf);
    }
}

// NuGet: Install-Package WkHtmlToPdf-DotNet
using WkHtmlToPdfDotNet;
using WkHtmlToPdfDotNet.Contracts;
using System.IO;

class Program
{
    static void Main()
    {
        var converter = new SynchronizedConverter(new PdfTools());
        var doc = new HtmlToPdfDocument()
        {
            GlobalSettings = {
                ColorMode = ColorMode.Color,
                Orientation = Orientation.Landscape,
                PaperSize = PaperKind.A4,
                Margins = new MarginSettings() { Top = 10, Bottom = 10, Left = 10, Right = 10 }
            },
            Objects = {
                new ObjectSettings()
                {
                    Page = "input.html",
                    WebSettings = { DefaultEncoding = "utf-8" }
                }
            }
        };
        byte[] pdf = converter.Convert(doc);
        File.WriteAllBytes("custom-output.pdf", pdf);
    }
}

IronPDF Approach:

// NuGet: Install-Package IronPdf
using IronPdf;
using IronPdf.Rendering;
using System;

class Program
{
    static void Main()
    {
        var renderer = new ChromePdfRenderer();
        renderer.RenderingOptions.PaperOrientation = PdfPaperOrientation.Landscape;
        renderer.RenderingOptions.MarginTop = 10;
        renderer.RenderingOptions.MarginBottom = 10;
        renderer.RenderingOptions.MarginLeft = 10;
        renderer.RenderingOptions.MarginRight = 10;
        renderer.RenderingOptions.PaperSize = PdfPaperSize.A4;

        var pdf = renderer.RenderHtmlFileAsPdf("input.html");
        pdf.SaveAs("custom-output.pdf");
    }
}

// NuGet: Install-Package IronPdf
using IronPdf;
using IronPdf.Rendering;
using System;

class Program
{
    static void Main()
    {
        var renderer = new ChromePdfRenderer();
        renderer.RenderingOptions.PaperOrientation = PdfPaperOrientation.Landscape;
        renderer.RenderingOptions.MarginTop = 10;
        renderer.RenderingOptions.MarginBottom = 10;
        renderer.RenderingOptions.MarginLeft = 10;
        renderer.RenderingOptions.MarginRight = 10;
        renderer.RenderingOptions.PaperSize = PdfPaperSize.A4;

        var pdf = renderer.RenderHtmlFileAsPdf("input.html");
        pdf.SaveAs("custom-output.pdf");
    }
}

wkhtmltopdf nests settings inside GlobalSettings and Objects, with MarginSettings as a separate object. IronPDF provides direct RenderingOptions properties with clear names like PaperOrientation, MarginTop, and PaperSize.

CLI to IronPDF Mapping

C# Wrapper API Mapping

Placeholder Syntax Migration

Issue 1: Header/Footer Placeholder Syntax

wkhtmltopdf: Uses square bracket syntax like [page] and [toPage].

Solution: Update to IronPDF's curly brace placeholders:

// Before (wkhtmltopdf)
FooterSettings = { Left = "Page [page] of [toPage]" }

// After (IronPDF)
renderer.RenderingOptions.HtmlFooter = new HtmlHeaderFooter
{
    HtmlFragment = "<div style='text-align:left;'>Page {page} of {total-pages}</div>",
    MaxHeight = 25
};

// Before (wkhtmltopdf)
FooterSettings = { Left = "Page [page] of [toPage]" }

// After (IronPDF)
renderer.RenderingOptions.HtmlFooter = new HtmlHeaderFooter
{
    HtmlFragment = "<div style='text-align:left;'>Page {page} of {total-pages}</div>",
    MaxHeight = 25
};

Issue 2: JavaScript Delay Configuration

wkhtmltopdf: Uses JavascriptDelay property with limited reliability.

Solution: IronPDF provides multiple options:

renderer.RenderingOptions.EnableJavaScript = true;

// Option 1: Fixed delay
renderer.RenderingOptions.WaitFor.RenderDelay(500);

// Option 2: Wait for specific element (more reliable)
renderer.RenderingOptions.WaitFor.HtmlElementById("content-loaded");

// Option 3: Wait for JavaScript condition
renderer.RenderingOptions.WaitFor.JavaScript("window.renderComplete === true");

renderer.RenderingOptions.EnableJavaScript = true;

// Option 1: Fixed delay
renderer.RenderingOptions.WaitFor.RenderDelay(500);

// Option 2: Wait for specific element (more reliable)
renderer.RenderingOptions.WaitFor.HtmlElementById("content-loaded");

// Option 3: Wait for JavaScript condition
renderer.RenderingOptions.WaitFor.JavaScript("window.renderComplete === true");

Issue 3: Modern CSS Not Rendering

Symptom: CSS Grid and Flexbox layouts render incorrectly in wkhtmltopdf.

Solution: IronPDF's Chromium engine handles modern CSS correctly:

// This CSS now works with IronPDF
var html = @"
<style>
    .grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; }
    .flex { display: flex; justify-content: space-between; align-items: center; }
</style>
<div class='grid'>
    <div>Column 1</div>
    <div>Column 2</div>
    <div>Column 3</div>
</div>";

var pdf = renderer.RenderHtmlAsPdf(html);

// This CSS now works with IronPDF
var html = @"
<style>
    .grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; }
    .flex { display: flex; justify-content: space-between; align-items: center; }
</style>
<div class='grid'>
    <div>Column 1</div>
    <div>Column 2</div>
    <div>Column 3</div>
</div>";

var pdf = renderer.RenderHtmlAsPdf(html);

Issue 4: Synchronous vs Asynchronous Rendering

wkhtmltopdf: Wrappers are synchronous and block threads.

Solution: IronPDF supports async rendering:

public async Task<byte[]> GeneratePdfAsync(string html)
{
    var renderer = new ChromePdfRenderer();
    var pdf = await renderer.RenderHtmlAsPdfAsync(html);
    return pdf.BinaryData;
}

public async Task<byte[]> GeneratePdfAsync(string html)
{
    var renderer = new ChromePdfRenderer();
    var pdf = await renderer.RenderHtmlAsPdfAsync(html);
    return pdf.BinaryData;
}

Pre-Migration Tasks

Audit your codebase to identify all wkhtmltopdf usage:

# Find all wkhtmltopdf references
grep -r "WkHtmlToPdfDotNet\|DinkToPdf\|TuesPechkin\|Rotativa" --include="*.cs" .
grep -r "wkhtmltopdf" --include="*.yml" --include="*.yaml" --include="Dockerfile" .

# Find all wkhtmltopdf references
grep -r "WkHtmlToPdfDotNet\|DinkToPdf\|TuesPechkin\|Rotativa" --include="*.cs" .
grep -r "wkhtmltopdf" --include="*.yml" --include="*.yaml" --include="Dockerfile" .

Locate and document wkhtmltopdf binary files for removal. Document current settings (paper size, margins, headers/footers).

Code Update Tasks

1. Remove all wkhtmltopdf wrapper NuGet packages
2. Remove wkhtmltopdf binaries (wkhtmltopdf.exe, wkhtmltox.dll)
3. Install IronPdf NuGet package
4. Update namespace imports from WkHtmlToPdfDotNet to IronPdf
5. Replace SynchronizedConverter with ChromePdfRenderer
6. Convert HtmlToPdfDocument patterns to direct rendering methods
7. Update GlobalSettings configurations to RenderingOptions
8. Convert margin configurations from MarginSettings to individual properties
9. Update placeholder syntax ([page] → {page}, [toPage] → {total-pages})
10. Add IronPDF license initialization at startup

Post-Migration Testing

After migration, verify these aspects:

• Visual comparison of PDF output (should improve with modern CSS support)
• Verify modern CSS rendering (CSS Grid and Flexbox now work)
• Test JavaScript-heavy pages
• Security scan to confirm no wkhtmltopdf binaries remain
• Load test for performance comparison

Security Verification

# Scan for any remaining wkhtmltopdf artifacts
find /var/www/ -name "*wkhtmlto*" 2>/dev/null
find /usr/local/bin/ -name "*wkhtmlto*" 2>/dev/null
docker images | grep wkhtmltopdf

# Check if any process is still using it
ps aux | grep wkhtmltopdf

# Scan for any remaining wkhtmltopdf artifacts
find /var/www/ -name "*wkhtmlto*" 2>/dev/null
find /usr/local/bin/ -name "*wkhtmlto*" 2>/dev/null
docker images | grep wkhtmltopdf

# Check if any process is still using it
ps aux | grep wkhtmltopdf