File Extension Database

Open CER File

CER extension files are security files provided and generated by a certification authority.

These files help the browser to verify if a website is secure and accessible without risk, verifying its authenticity.

These CER security certificates are typically installed on a web server.

If a user enters a URL to a website hosted on the same server, the browser checks the validity of the website by checking the attached certificate.

The public certificate included in the CER file maps a public key to a specific identity using a digital signature, which verifies the website.

Different encryption algorithms, such as Base 64 and DER, can be used to encrypt the contents of a CER certificate.

When browsing a validated website, the corresponding CER certificate can be viewed by clicking the padlock icon located on the browser page (usually located on the edge).

It is available for SSL-encrypted websites and can be easily detected by the "https://" prefix in the URL.

By double-clicking on said lock, it is possible to see the information contained in the CER file, at least in Edge, Firefox and Safari.

Software to open and work with a CER file

Typical CER application file locations:

%SystemRoot%\system32\rundll32.exe cryptext.dll
C:\Windows\system32\rundll32.exe cryptext.dll,CryptExtOpenCER %1

Typical CER mime types:

CryptExtOpenCER %1
application/x-x509-ca-cert

Frequently associated Windows objects:

CERFile

How Can I Open CER File on Windows

We researched and learned that the best way to open CER file is to find a CER file in question in Windows OS File Explorer and double click on it to launch the corresponding application.
If a CER file is not opened in an application and you instead get a "Windows can't open a file" error message you should try looking for an application which can open the file in question.
If you know the application which can open CER file then run it and see if there is a File->Open main menu option in the application.
If you don't know the application which function as CER file opener then try to search online for "CER viewer", "application to open CER file" or "open CER file" queries in the search engine you like.
Install the application you found and check if it can open CER file

How Can I Open CER File on Mac OS

We recommend to find a CER file in question in Mac OS Finder and double click on it to launch the corresponding application.
If a CER file is not opened in a Mac OS application and you instead get a "There is no application set to open the file" error message you can click on "Search App Store" in the error dialog and Mac OS will show you applications compatible with CER file.
If you know the Mac OS application which can work as CER file opener you can choose the "Choose Application..." option in the error box to associate the file extension and open CER file in it.
If you don't know the application which can open CER file then try to search for "CER viewer", "application to open CER file" or "read CER file" queries in the online search engine you like.
Install the application you found and check if it can read CER file

How Can I Open CER File on Android

If you downloaded a CER file on Android device you can open it by following steps below:

In the Android apps list on your Android device find "My Files" or "File manager" app and tap to start it.
Tap on "Downloads" folder inside the app.
You should see your downloaded CER file in that folder.
Tap on the file. If Android device supports opening the file you downloaded it will open in the corresponding app.
If file does not open you can look for the corresponding app that can open the file by searching Android App Store for the "CER".
If you cannot open the file with the apps from Android App Store it is possible that the file could only be opened on desktop platforms such as Windows or Mac OS. Try searching for "CER viewer", "CER file reader" online and see if any desktop applications can open it.
It is also possible that the file you downloaded is outdated and is no longer supported.

How to Open CER File on iPhone or iPad

To open CER File on iOS device follow steps below:

We advies to open Files app on your iPhone or iPad device. You can find it by swiping down on the home screen and typing "Files" in the search bar.
Tap on the Downloads folder on the Files app home screen.
You will see all files that you recently downloaded. Tap on the CER file to view it.
If you have the right app that can open it it will automatically launch and open your file.
If you don't have the app which can open it you need to serch Apple app store for "CER". This way you can find apps which can open CER files.
If this doesn't help it is possible that your file could be opened only by the desktop application. To find an app which can open it on desktop look for "CER viewer" or "CER file" online in your favorite search engine.

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