Opening a CER File

The CER file type is primarily associated with OpenSSL.

CER	File extension: CER
	File type:	public key certificate

What is a CER file?

CER files mostly belong to OpenSSL by OpenSSL. A CER file is an X.509 public key certificate which Internet browsers use to verify the source and authenticity of a web page. This certificate is securely saved on a website and shared with clients requesting a resource from the website. OpenSSL can be used to generate a CER certificate. Chrome, Firefox, Edge, and other modern web browsers support CER certificates. Another type of CER file is an error message generated by Lahey Fortran compiler when an error occurs during program compilation.

How can I open a CER file?

You need a suitable software like OpenSSL to open a CER file. Without proper software you will receive a Windows message "How do you want to open this file?" or "Windows cannot open this file" or a similar Mac/iPhone/Android alert. If you cannot open your CER file correctly, try to right-click or long-press the file. Then click "Open with" and choose an application. You can also display a CER file directly in the browser:. Just drag the file onto this browser window and drop it.

Online CER File Viewer

Choose your .cer file to view

or drag and drop it here

Online File Viewer

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How to extract texts from CER files or capture a screenshot to PDF, JPG, DOCX, TXT, ...

You can extract texts from CER file or capture a preview screenshot using our online CER file viewer:

Just click the "Choose your .cer file to view" button on this page.
After your file is opened in browser,
click "Save as..." in the menu.
Then choose the file format (e.g. JPG, PDF, DOCX, TXT, ...) you want.
Download the converted file.

Programs that open and convert CER files:

OpenSSL by OpenSSL
See the previous paragraphs to learn more about the main application. CER files are often referred to as OpenSSL web (source)s because this type of file is primarily created or used by this software.
Cerius2 (chemical data) by Accelrys
Cerius2 is a discontinued modeling and simulation environment for scientific operations. This program was compatible with UNIX-based platforms. It saved chemical data in a CER file coded in MSI Cerius II format. This file format is classified as Data.
Chrome (public key certificate) by Google
Chrome is an Internet browser based on Chromium. It uses a CER file containing a public key certificate to authenticate a website. This file format is classified as Web (source).
Creatacard (certificate project) by Broderbund
Creatacard is a discontinued greeting card design and publishing software for Windows desktop. It saves a certificate project in a CER file. This file format is classified as Page Layout.
Edge (public key certificate) by Microsoft
Edge is a Chromium-based web browser bundled with Windows operating system. It can read a website's public key certificate saved in a CER file. This file format is classified as Web (source).
Firefox (public key certificate) by Mozilla
Firefox is a cross-platform web browser with a large collection of add-ons. It can read a CER file containing a website's public key certificate. This file format is classified as Web (source).
Lahey Fortran (compilation error message) by Lahey
Lahey Fortran is an integrated development environment featuring a compiler for Fortran programming language. It saves a compilation error message in a CER file. This file format is classified as Simple text file.
Print Artist (certificate document) by Sierra
Print Artist is a discontinued desktop publishing application with thousands of templates and graphical objects for creating documents. It saves a certificate in a CER file. This file format is classified as Page Layout.

CER file format:

Why is it important to know the file format? This is the only way to find out which program to use to open the file. The first characters in a file identify the file format, for example, HTML files start with the bytes <html>. If the file extension does not match the file format, double-clicking on the file will cause an error upon opening. Exact knowledge of the format is therefore important in order to solve problems occurring in files. In the following you will find our evaluation of the CER files:

The CER file extension is quite widespread and covers different formats for different programs. But the following two file formats are common:

65% of all CER files are based on the popular certificate file format. A digital certificate is a unique, digitally signed document which authoritatively identifies the identity of an individual or organization. Using public key cryptography, its authenticity can be verified to ensure that the software or website you are using is legitimate. The contents of these files cannot be read by a human; only a computer program can interpret the data. The file size is in the range of 750 bytes to 1 KB. The file type is relatively new. These files are attributed to cert, certificate, root, exchange, microsoft, certnew, signing and server.
25% of all CER files are associated with Internet Security Certificate files, which internally utilize the well-known KEY format. A public or private key is used in Public-key cryptography to digitally sign or verify documents, software or websites, or to authentice a user. These files are plain text, which means they can be viewed with any text editor such as Windows Editor, Nano for Linux, and TextEdit for macOS. The files are often between 1 KB and 2 KB in size. Certain words are almost always found in the files, such as ----BEGIN CERTIFICATE----. These files can be linked to publickey, base, bundle, rootca, star, cacert, device, public and prod.

All other CER files (10%) have no consistent format, often, for example, DOC and MII. Often described as issuing, sign, global, apple, digi, signature, digital, azure or token. If you want to find out what your CER file contains, drag and drop it onto this page.

Technical Data for CER File Extension

File classification:

Web (source)

Related files:

crt, pem, der, cert, p7b, p12, pfx, key, sgn, jks, req, csr, txt, pkcs8, cacerts, appxsym, cre, p7c, car, certificate

Related links:

Certificate filename extensions

Mime type:

application/pkix-cert, application/x-x509-ca-cert

The following listing is compiled from the database produced by the 'Associate This!' program, selected data from the main FILExt database and file extension information submitted by users.

ProgramID: CERFile, FileType: Security Certificate, AppName: Crypto Shell Extensions
EXEFile: cryptext.dll

ProgramID: certificatefile, FileType: Internet Security Certificate, AppName: Internet Control Panel

ProgramID: CERFile
EXEFile: %SystemRoot%\system32\rundll32.exe cryptext.dll,CryptExtOpenCER %1

ProgramID: CERFile
EXEFile: rundll32.exe cryptext.dll,CryptExtOpenCER %1

ProgramID: PMWCertificateType
EXEFile: %ProgramFiles%\The Print Shop 20\tps.exe %1

ProgramID: PMWCertificateType
EXEFile: %ProgramFiles%\BRODER~1\PROFES~1\pppbl.exe %1

ProgramID: PMWCertificateType
EXEFile: %ProgramFiles%\BRODER~1\AGCREA~1\agccard.exe %1

ProgramID: CERFile
EXEFile: rundll32.exe %SystemRoot%\ServicePackFiles\i386\cryptext.dll,CryptExtOpenCER %1

ProgramID: PMWCertificateType
EXEFile: %ProgramFiles%\PrintMaster 16\pm.exe %1

ProgramID: PMWCertificateType
EXEFile: %ProgramFiles%\The Print Shop 21\tps.exe %1

ProgramID: PMWCertificateType
EXEFile: %ProgramFiles%\BRODER~1\PRINTM~1\pmw.exe %1

ProgramID: PMWCertificateType
EXEFile: %ProgramFiles%\Scrapbook Designer\scrapbook.exe %1

ProgramID: PMWCertificateType
EXEFile: %ProgramFiles%\PrintMaster Platinum 17\PMW.exe

Show all 13 listings To Top

a cer public key certificate is a special file format by OpenSSL and should only be edited and saved with the appropriate software.

How to solve problems with CER files

Associate the CER file extension with the correct application.
Update your software that should actually open public key certificates. Because only the current version supports the latest CER file format. Search, therefore, e.g. on the OpenSSL manufacturer website after an available OpenSSL update.
To make sure that your CER file is not corrupted or virus-infected, get the file again and scan it with Google's virustotal.com.
Click here to open your .CER file online - secure, fast, and no downloads needed.