Initial render is slow

If your first HTML-to-PDF render with IronPDF is slow, we may be looking at the following underlying issues:

Initiation Checks

IronPDF will check to ensure that CEF browser DLLs required to execute are available.


  • IronPdf.Slim is the base package for our Chrome-identical rendering engine. Using this package alone may allow the most flexibility but will require more time to initiate as the required files are retrieved from the NuGet CDN.

CEF browser application start-up time

The initial render may take 2-3 seconds to execute. This is normal start-up time that is similar to the time it takes for Chrome to open on a desktop environment.


  • Use IronPdf.Installation.Initialize earlier in your application to initialize IronPDF rendering engines immediately, to avoid start-up time on your first render when called.
  • Before Installation.Initialize was introducted, another option was to pre-render a dummy PDF during application start-up (prior to the planned render). This will allow any additional files required for the planned PDF render to already be loaded and waiting.  Please remember this start-up overhead only affects the first render job after your application is restarted.
  • If initialization is taking more than 5 seconds, the server or PC may be under-provisioned. We would recommend using a more powerful server or Azure Web app plan (B1 is the minimum).