Click the "Select File" button above, and choose your CER file.
You'll see a preview.
Click the "Convert file to..." button to save your file in the format you want.
Convert CER to another file type
The converter easily converts your CER file to various formats - free and online. No Excel or extra software needed.
Convert a file to CER
The converter also works in reverse, so you can convert other System formats to CER with high quality output.
About CER files
A .CER file is a digital security certificate used to authenticate the identity of a website or organization, crucial for establishing encrypted SSL/TLS connections. These files adhere to the X.509 standard and contain a public key, but they are notorious for causing friction due to encoding ambiguity. A .CER file can be encoded as binary (DER) or text (Base64 PEM), yet the extension remains the same. This often results in compatibility errors when moving certificates between operating systems; for instance, Microsoft IIS defaults to .CER, while Linux servers running Apache or Nginx typically require CRT or PEM extensions to function correctly. Additionally, .CER files rarely contain the private key, which can lead to stalled server migrations if users don't realize they need to pair it with a separate key file or convert it to a PFX container. To fix these issues, users often need to convert .CER files: use PEM/CRT for Linux-based web hosting and text editors, DER for Java keystores, or PFX for backing up the certificate chain with its private key.
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 "Digital 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 "Digital 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.