CRL File

What are CRL files and how to open them

Are you having problems opening a CRL file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your CRL files.

What is a CRL file?

CRL files have multiple uses, and Calamus Ruler List is one of them. Read more about the other uses further down the page.

Calamus Ruler List

A .crl file, also known as a Calamus Ruler List file, is a text document used by the professional desktop publishing software Calamus for the Atari ST platform. It contains information about the rulers and grids used in a Calamus document, such as the unit of measurement, size and position of rulers, and visibility settings.

The .crl file stores the settings for rulers and grids so that users can save them for reuse in different documents. With these settings, rulers can measure and align elements in a document to ensure accuracy, while grids act as references for positioning elements.

Calamus is an older software that is no longer widely used, so it's important to note that .crl files may not be compatible with modern desktop publishing programs.

How to open CRL files

Important: Different programs may use files with the CRL file extension for different purposes, so unless you are sure which format your CRL file is, you may need to try a few different programs.

We have not yet verified any programs for Windows that work with this specific file format. If you know one, please use the 'Suggest a program' link below. Thanks!

Last updated: August 5, 2026

All known file formats using extension .CRL

While Calamus Ruler List is a popular type of CRL-file, we know of 2 different uses of the .CRL file extension. Different software may use files with the same extension for different types of data.

Certificate Revocation List

A Certificate Revocation List (CRL) file is used in public key infrastructure (PKI) systems to record certificates that have been revoked before their scheduled expiration and must no longer be trusted. The issuing Certificate Authority (CA) generates this list and signs it digitally; software that checks certificate validity downloads a CRL and compares certificate serial numbers to those listed. The CRL ensures that even certificates that were valid when issued can be declared unsafe later if, for example, the private key was compromised.

CRL files typically follow the X.509 v2 standard and are encoded using ASN.1 notation. They include fields for the version, signature algorithm, issuer name, the date and time the list was last updated, the date when the next CRL will be issued, and a sequence of entries each consisting of a revoked certificate's serial number, date of revocation, and optionally extensions. The CA's signature covers most of this data and validates the list's integrity. RFC 5280 defines this structure in detail.

CRL files are commonly encoded in either DER (binary) or PEM (Base64 with header/footer) form. In PEM format, they begin with "-----BEGIN X509 CRL-----" and end with "-----END X509 CRL-----", wrapping the DER-encoded data. OpenSSL is a typical tool used to create, read, convert, or verify .CRL files, supporting both DER and PEM formats.

CRL opener for Windows

We have identified one CRL opener that is compatible with this specific type of CRL file.

Help us help others

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