This site will have limited functionality while we undergo maintenance to improve your experience. If an article doesn't solve your issue and you want to ask a question, we have our support community waiting to help you at @FirefoxSupport on Twitter and/r/firefox on Reddit.

Avatar for Username

Buscar en Ayuda

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

Este tema ha sido archivado. Haz una nueva pregunta si necesitas ayuda.

Firefox not starting

  • 2 respuestas
  • 1 tiene este problema
  • 2 visitas
  • Última respuesta de FredMcD

1cakethecake1
1cakethecake1
more options

Whenever i try to open firefox it shows a window briefly before closing immediately i've tried: reinstalling deleting all files related to firefox and reinstalling allowing through firewall checking for iseguard64.exe starting in safemode starting the profile manager through run and cmd

Whenever i try to open firefox it shows a window briefly before closing immediately i've tried: reinstalling deleting all files related to firefox and reinstalling allowing through firewall checking for iseguard64.exe starting in safemode starting the profile manager through run and cmd

Todas las respuestas (2)

FredMcD
FredMcD
more options

This could be caused by several issues.


Some problems occur when your Internet security program was set to trust the previous version of Firefox, but no longer recognizes your updated version as trusted. Now how to fix the problem: To allow Firefox to connect to the Internet again;

  • Make sure your Internet security software is up-to-date (i.e. you are running the latest version).
  • Remove Firefox from your program's list of trusted or recognized programs. For detailed instructions, see

Configure firewalls so that Firefox can access the Internet. {web link}

FredMcD
FredMcD
more options

You can check for issues caused by a corrupted or incomplete Visual C++ installation that is missing runtime components (Redistributable Packages) required by Firefox, especially VCRUNTIME140_1.dll.

Install both 32-bit and 64-bit "Visual Studio 2015, 2017 and 2019" downloads, (x86: vc_redist.x86.exe and x64: vc_redist.x64.exe) from https://support.microsoft.com/help/2977003/the-latest-supported-visual-c-downloads