Types of DER Files

Principal DER Type

.DER

File Ext:	.der
Type:	DER Certificate File

A DER file is created in the Distinguished Encoding Rules (DER) format. It is used for storing X.509 certificates in public cryptography.

Author:	Mozilla
File Category:	Web Files
Folder:	HKEY_CLASSES_ROOT\.der

Software Programs That Open The DER Certificate File:

Internet Explorer by Microsoft Corporation

Windows

Mac

Mozilla Firefox by Mozilla

Windows

	Mac
	iOS

Android

Linux

Solaris

illumos

Apple Safari by Apple

Windows

	Mac
	iOS

Android

Linux

Solaris

illumos

Apple Keychain Access by Apple

Mac

OS X El Capitan

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DER File Complications

Common Problems Opening DER Files

Internet Explorer Disappeared

When you double-click your DER file, you may see a dialog box from your operating system stating that it "Cannot Open This File Type". When this happens, it is commonly due to Internet Explorer missing in %%os%%. Because your operating system doesn't know what to do with this file, you won't be able to open it by double-clicking.

Tip: If you have another software that you know opens DER files, you can select it by hitting the "Show Apps" button.

Internet Explorer is Out-of-Date

Occasionally, you might have an outdated version of Internet Explorer installed that's incompatible with your DER Certificate File type. Installing the latest version of Internet Explorer from Microsoft Corporation is recommended. This problem is most common when you have an older version of the software application, and your file was created by a newer version that it cannot recognize.

Tip: If you right-click on your DER file, then select "Properties" (Windows) or "Get Info" (Mac), you can obtain hints about what version you need.

Conclusion: The majority of DER file opening issues are due to not having the correct Internet Explorer version installed.

Associated Difficulties Loading DER Files

Although you might already have Internet Explorer or another DER-associated software installed on your computer, you can still encounter problems opening DER Certificate File files. There can be external issues inside of %%os%% that are causing these errors when opening DERs. Problems unrelated to software:

• DER file type Registry entries are wrong
• The DER file description within the Windows Registry was removed
• Incomplete or bad installation of a software application associated with the DER format
• File corruption affecting your DER file
• DER file integrity has been compromised by malware
• DER-related hardware has device drivers that obsolete
• Insufficient system resources to successfully open DER Certificate File files