Opening DER Files

The DER file type is primarily associated with OpenSSL.

DER	File extension: DER
	File type:	public key certificate

What is a DER file

DER files mostly belong to OpenSSL by OpenSSL. A DER file is a public key certificate used to authenticate data transferred over HyperText Transfer Protocol Secure (HTTPS). Its contents are saved as binary data using Distinguished Encoding Rules (DER) which produce unique digitally signed X.509 certificates for binding a public and private key. Cryptography tools such as OpenSSL can generate a DER certificate. Internet clients like download managers and web browsers (e.g. Chrome and Edge) support DER certificates. Distinguished Encoding Rules is also used in CER, PEM, and DER certificates.

How to open DER files

You need a suitable software like OpenSSL to open a DER 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 DER file correctly, try to right-click or long-press the file. Then click "Open with" and choose an application. You can also display a DER file directly in the browser:. Just drag the file onto this browser window and drop it.

Online DER Text Viewer

Choose your .der file to analyze

or drag and drop it here

Online File Viewer

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DER file format:

The file format determines how the data is stored in the file. Each file format has a unique extension and almost always a unique signature. For example, Microsoft Word documents have the extension .docx and the signature (usually the first 3 characters in this file) PK. However, different programs can use the same file extension, and file extensions can be assigned incorrectly. If there are problems opening a file, you must first determine the file format used. Our evaluation of the DER files looks like this:

The DER extension is very commonly used. This DER file itself is among the most popular common file types and mainly uses a defined DER format. The two most common formats are as follows:

• 80% of all DER files are DER encoded X509 Certificate files, which are using 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 content consists of illegible binary data, which can only be read and interpreted by the associated programs. Most of these files are 290 bytes to 1 KB in size. The file type was developed only in the last few years. These files are attributed to cert, public, private, deployment, upload, certificate, cacert and root.
• 4% of all DER files save the data in certificate file format. They consist of unreadable binary data. The files are on average 160 bytes in size and range from 160 bytes to 240 bytes. A common filename is file.der or public.der.

All other DER files (16%) have no uniform format. They are often associated with pubkey, sign, server, fbeb, yggdrasil or session. If you want to find out what your DER file contains, drag and drop it onto this page.