What is YTSingleInstance.dll?

The genuine YTSingleInstance.dll file is a software component of Yahoo! Toolbar Single Instance for Mail by Yahoo!.
YTSingleInstance.dll is a DLL (dynamic link library) file that stores data, code and resources needed by the program to function properly. This process is a BHO (browser helper object), a plugin designed to add functionality to Microsoft's Internet Explorer. The Yahoo! Toolbar was originally intended as a simple pop-up blocker but has evolved into a whole application that provides shortcuts to various websites, offers bookmarking tools and a search feature powered by Yahoo! Inc. is an American company that is famous for its website, search engine, and many services it offers including Yahoo! Mail and Yahoo! News. Yahoo! has over 700 million visits per month, making it one of the most popular websites based in the US. Yahoo! was founded by David Filo and Jerry Yang in 1994. It is headquartered in Sunnyvale, California.

YTSingleInstance stands for Yahoo! Toolbar Single Instance for Mail

YTSingleInstance.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 Yahoo! Single Instance.

Click to Run a Free Scan for YTSingleInstance.dll related errors

YTSingleInstance.dll file information

The process known as Yahoo! Single Instance for Mail belongs to software Yahoo! Single Instance for Mail or Yahoo! Toolbar or Heroes of Might and Magic IV or Sony on Yahoo! Essentials or Boris Graffiti or Adobe Photoshop Lightroom by Yahoo! (

Description: YTSingleInstance.dll is not essential for the Windows OS and causes relatively few problems. YTSingleInstance.dll is located in a subfolder of "C:\Program Files" or sometimes in a subfolder of the user's "Documents" folder or in a subfolder of the user's profile folder. Known file sizes on Windows 10/8/7/XP are 160,496 bytes (42% of all occurrences), 163,128 bytes and 9 more variants. 
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 FDAD4DA1-61A2-4FD8-9C17-86F7AC245081. YTSingleInstance.dll is a Verisign signed file. The program is not visible. The YTSingleInstance.dll file is able to monitor web browsers. It is digitally signed. There is no detailed description of this service. The YTSingleInstance.dll file is not a Windows core file. Therefore the technical security rating is 48% dangerous, however you should also read the user reviews.

Uninstalling this variant: If you have any problems with YTSingleInstance.dll, you may also completely remove Yahoo! Toolbar or Sony on Yahoo! Essentials (Control Panel ⇒ Uninstall a Program).

Recommended: Identify YTSingleInstance.dll related errors

Important: Some malware camouflages itself as YTSingleInstance.dll, particularly when located in the C:\Windows or C:\Windows\System32 folder. Therefore, you should check the YTSingleInstance.dll process on your PC to see if it is a threat. If Yahoo! Single Instance 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

I Scanned this file with 40 diffrent anti virus programs on an online site called VirusTotal Free Online Virus And Malware Scan and it found no viruses or malware so i think its safe to say this file is A-OK!
It's a BHO. (Browser Helper object). It starts everytime you open the internet browser and is not dangerous unless it is a disguised malware program.
  Montekristo   (further information)

Summary: Average user rating of YTSingleInstance.dll: based on 2 votes with 2 user comments. 2 users think YTSingleInstance.dll is essential for Windows or an installed application.

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Best practices for resolving YTSingleInstance issues

The following programs have also been shown useful for a deeper analysis: ASecurity Task Manager examines the active YTSingleInstance process on your computer and clearly tells you what it is doing. Malwarebytes' well-known Banti-malware tool tells you if the YTSingleInstance.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 1cleanmgr and 2sfc /scannow, 3uninstalling programs that you no longer need, checking for Autostart programs (using 4msconfig) and enabling Windows' 5Automatic 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 6resmon 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 7DISM.exe /Online /Cleanup-image /Restorehealth command. This allows you to repair the operating system without losing data.

Other processes

YTSingleInstance.dll [all]