What is companioncore.dll?

The genuine companioncore.dll file is a software component of Windows Live Messenger Companion by Microsoft.
"companioncore.dll" is a Windows Internet Explorer browser helper object for Microsoft's Companion within Windows Live and Messenger. It monitors your website visits and detects when you visit a website that friends have shared content on in Microsoft Live. It then shows you their content while allowing you to interact and comment on it within Windows Live. Microsoft not only provides leading operating system software, but also develops many applications and products worldwide, since 1975.

Companioncore.dll is a browser extension for Internet Explorer. This add-on enables several additional functions for Internet Explorer. You can disable it through the Extras menu (key combination Alt + X) under Manage Add-ons. The following paragraph provides more information about Windows Live Messenger Companion Core.

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Companioncore.dll file information

The process known as Windows Live Messenger Companion Core belongs to software Windows Live Messenger Companion or Windows Live Essentials or Windows Live Messenger Companion Core by Microsoft (

Description: Companioncore.dll is not essential for the Windows OS and causes relatively few problems. Companioncore.dll is located in a subfolder of "C:\Program Files" or sometimes in a subfolder of the user's profile folder. Known file sizes on Windows 10/8/7/XP are 393,600 bytes (99% of all occurrences), 380,800 bytes, 299,880 bytes or 387,952 bytes. 
This .dll file is a Browser Helper Object (BHO) that runs automatically every time you start your web browser. BHOs are not stopped by personal firewalls, because they are identified by the firewall as part of the browser itself. BHOs are often used by adware and spyware. IDs used by this BHO include 9FDDE16B-836F-4806-AB1F-1455CBEFF289. The program has no visible window. It is able to monitor web browsers. The file is digitally signed. There is no detailed description of this service. Companioncore.dll is not a Windows system file. You can uninstall this program in the Control Panel. Companioncore.dll is able to record keyboard and mouse inputs. Therefore the technical security rating is 50% dangerous, however you should also read the user reviews.

Uninstalling this variant: In case of any problems with companioncore.dll, you can do the following:

Recommended: Identify companioncore.dll related errors

Important: Some malware camouflages itself as companioncore.dll, particularly when located in the C:\Windows or C:\Windows\System32 folder. Therefore, you should check the companioncore.dll process on your PC to see if it is a threat. If Windows Live Messenger Companion Core has changed your browser's search engine and start page, you can recover your browser's default settings as follows:

Reset default browser settings for Internet-Explorer ▾
  1. In Internet Explorer, press the key combination Alt + X to open the Tools menu.
  2. Click Internet options.
  3. Click the Advanced tab.
  4. Click the Reset... button.
  5. Enable the Delete personal settings option.
This will reset your Internet Explorer to its default settings. Your browser will start with the familiar start page and search engine—without popups, ads, cookies, but all browser add-ons are deleted too [1]. Make cleaning up your browser and your computer simpler and safer with Security Task Manager.


User Comments

part of Windows Live Messenger
  meehee   (further information)
Gets louded with Windows Live Programs
Windows Live Messenger Companion Core - Windows Live Messenger Companion is an add-in for Windows Internet Explorer that detects when a user is on a website that one of their friends has shared content from and surfaces that update so that the user can instantly view what their friends have shared and leave a comment to the shared content on Windows Live. The service utilizes Windows Live ID and integrates tightly with Windows Live Messenger to obtain the user's contact list and their shared contents.
  JPD   (further information)

Summary: Average user rating of companioncore.dll: based on 4 votes with 3 user comments. 4 users think companioncore.dll is essential for Windows or an installed application.

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Best practices for resolving companioncore issues

The following programs have also been shown useful for a deeper analysis: Security Task Manager examines the active companioncore process on your computer and clearly tells you what it is doing. Malwarebytes' well-known anti-malware tool tells you if the companioncore.dll on your computer displays annoying ads, slowing it down. This type of unwanted adware program is not considered by some antivirus software to be a virus and is therefore not marked for cleanup.

A clean and tidy computer is the key requirement for avoiding PC trouble. This means running a scan for malware, cleaning your hard drive using cleanmgr and sfc /scannow, uninstalling programs that you no longer need, checking for Autostart programs (using msconfig) and enabling Windows' Automatic Update. Always remember to perform periodic backups, or at least to set restore points.

Should you experience an actual problem, try to recall the last thing you did, or the last thing you installed before the problem appeared for the first time. Use the resmon command to identify the processes that are causing your problem. Even for serious problems, rather than reinstalling Windows, you are better off repairing of your installation or, for Windows 8 and later versions, executing the DISM.exe /Online /Cleanup-image /Restorehealth command. This allows you to repair the operating system without losing data.

Other processes

companioncore.dll [all]