Click the "Select File" button above, and choose your CER file.
You’ll see a preview, if available.
Click the "Convert file to..." button to extract text information.
Convert CER to another file type
To convert CER Certificates to another format, you need OpenSSL or other Web software.
Convert a file to CER
To convert other file formats to the "X.509 Security Certificate" file type, you need software like OpenSSL or a similar tool.
About CER files
A .CER file is a standard digital security certificate based on the X.509 standard. System administrators use these files to verify the identity of web servers and establish secure SSL/TLS connections. Native operating systems like Windows can open these files directly, while server environments manage them using utilities like OpenSSL or Microsoft Certificate Services. The primary disadvantage of the .CER format is its ambiguous encoding. A .CER file can be either binary encoded (DER) or Base64 encoded (PEM). This creates major compatibility issues. For example, Windows servers often generate binary .CER files, which fail immediately when uploaded to Linux-based Apache or Nginx servers expecting a text-based PEM structure. Furthermore, .CER files strictly contain public keys - you cannot use them to secure a server without pairing them with the matching private key. To fix encoding errors for web servers, convert your .CER file to a PEM or CRT format. If you need to import the certificate into Windows IIS with its private key, you must combine it into a PFX or P12 archive. Drop your file here to view and convert it securely right in your browser without installing command-line tools.
Convert.Guru analyzes your CER file, detects the exact format, and lets you read the text inside.
If you want to convert CER file to PEM, PFX, CRT, P12, JKS, HTML, HTM, CSS, JS, PHP, ASP or ASPX, you can use OpenSSL or similar software from the "Internet Security Certificate" category. In the File menu, look for Save As… or Export….
To convert RSS, CSS, CGI, SITEMAP, PL, WEBMANIFEST, JSON, JS, XML, HTML, ICO or HTM files to CER, try OpenSSL or another comparable tool in the "Internet Security Certificate" category.
The CER Converter Story
The history of Convert.Guru began over 25 years ago in California with Tom Simondi’s file-format database. A former contributor to Space Shuttle development and a software pioneer of the 1980s, Simondi established a trusted resource for file type analysis that was even referenced by Microsoft Windows XP. Today, we use modern technology to process and convert thousands of file formats while continually improving our CER converter.