Fixing PDF Rendering Timeout Issues

Chaknith Bin

Updated:June 22, 2025

Unable to Render PDF from HTML
Unable to Render PDF from URL
Error while generating PDF from HTML
Error while generating PDF from URL
Unspecified native exception

These generic error messages indicate that the Chrome rendering engine has encountered a failure.

Applying the code snippet below will produce a "Default.log" log file that can help in determining the cause of the failure.

// Enable logging for all events and set the file path for the log file.
IronPdf.Logging.Logger.LoggingMode = IronPdf.Logging.Logger.LoggingModes.All;
IronPdf.Logging.Logger.LogFilePath = "Default.log";

// Enable logging for all events and set the file path for the log file.
IronPdf.Logging.Logger.LoggingMode = IronPdf.Logging.Logger.LoggingModes.All;
IronPdf.Logging.Logger.LogFilePath = "Default.log";

' Enable logging for all events and set the file path for the log file.
IronPdf.Logging.Logger.LoggingMode = IronPdf.Logging.Logger.LoggingModes.All
IronPdf.Logging.Logger.LogFilePath = "Default.log"

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Render Timeout

Timeout is a feature implemented in IronPDF to prevent applications from deadlock and becoming unresponsive due to long PDF rendering durations. This can help users by managing resources, ensuring that resources such as CPU, memory, and network bandwidth are not tied up with processes that take too long to complete. A timeout error, as described below, will be thrown if the PDF rendering process does not get completed in time.

Timeout after 60s while rendering PDF from HTML
Timeout after 60s while rendering PDF from URL
Timeout while generating PDF from HTML
Timeout while generating PDF from URL
Timeout while rendering PDF from HTML
Timeout while rendering PDF from URL

There are many reasons for long rendering times in IronPDF that could lead to timeout errors, such as rendering large or heavy PDFs, retrieving remote resources/assets for rendering PDFs, or issues during rendering itself. However, overriding the timeout duration can usually remedy the issue.

To override the default setting, users can access the Timeout property in the ChromePdfRenderOptions class and set it to a higher value.

// Set the timeout for rendering to 120 seconds.
RenderingOptions.Timeout = 120; // seconds

// Set the timeout for rendering to 120 seconds.
RenderingOptions.Timeout = 120; // seconds

' Set the timeout for rendering to 120 seconds.
RenderingOptions.Timeout = 120 ' seconds

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Please note

Starting from version 2021.12.4995, IronPDF's default rendering timeout is 60 seconds.

Render Delay

On some occasions, IronPDF may render:

A blank PDF
A PDF with incomplete content
A PDF with missing image assets

This issue might occur because the PDF document was rendered before the call to retrieve the contents or assets from the resource was completed in time.

Applying a render delay to the PDF renderer usually helps in remedying the issue. This will instruct the renderer to delay the PDF rendering for a set duration, so that the contents or assets can be loaded in time before PDF rendering. To do this, simply access the RenderDelay() method in the WaitFor wrapper object, set the desired duration time as the method parameter, and apply it to the renderer as one of the ChromePdfRenderOptions properties.

// Set a render delay of 5000 milliseconds (5 seconds) to ensure content and assets are loaded before rendering.
RenderingOptions.WaitFor.RenderDelay(5000);  // milliseconds

// Set a render delay of 5000 milliseconds (5 seconds) to ensure content and assets are loaded before rendering.
RenderingOptions.WaitFor.RenderDelay(5000);  // milliseconds

' Set a render delay of 5000 milliseconds (5 seconds) to ensure content and assets are loaded before rendering.
RenderingOptions.WaitFor.RenderDelay(5000) ' milliseconds

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Please note

The default RenderDelay duration is 20 ms

Apart from the RenderDelay() method, there are also other methods in the WaitFor wrapper object that can be utilized.

For further information about logs and how to report an error to our engineers for review, please see How to Make an Engineering Support Request for IronPDF.

Chaknith Bin

Chat with engineering team now

Software Engineer

Chaknith works on IronXL and IronBarcode. He has deep expertise in C# and .NET, helping improve the software and support customers. His insights from user interactions contribute to better products, documentation, and overall experience.