CLK File

What are CLK files and how to open them

Are you having problems opening a CLK 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 CLK files.

What is a CLK file?

CLK files have multiple uses, and ClickFORMS data is one of them. Read more about the other uses further down the page.

ClickFORMS data

These CLK files contain the appraisal reports created in ClickForm, a Point and Click appraisal software. These appraisals usually are reports done on real-estate properties for insurance or taxation purposes.

How to open CLK files

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

Programs that open ClickFORMS data files

Last updated: August 31, 2026

All known file formats using extension .CLK

While ClickFORMS data is a popular type of CLK-file, we know of 4 different uses of the .CLK file extension. Different software may use files with the same extension for different types of data.

Cloak Encrypted Data

Cloak Encrypted Data files store content that has been securely encrypted by the Cloak tool, so that sensitive information can be protected when agents, automated tools or other parties have access to the file system. The format is used when Cloak's agent encrypts an ordinary file (for example a text document) into a shareable encrypted package, while ensuring that only authorized humans (or processes) can decrypt it and revealing a signed receipt of the action.

Encryption is carried out locally on the writing machine using software keys under Cloak's governance framework. The plaintext never leaves the machine at the moment of encryption. The resulting file contains ciphertext plus enough metadata for Cloak to later decrypt for humans who have the appropriate identity or rights and to verify that the encryption operation was properly recorded via a digital receipt.

Section "Vault binary format" in the implementation details reveals the internal layout of these encrypted files. They begin with the ASCII magic value CLK in the first three bytes, followed by a version byte (currently 0x01). After that come a 12-byte initialization vector or nonce, then a 16-byte AES-256-GCM authentication tag, and finally the ciphertext.

While we have not verified the apps ourselves yet, our users have suggested ten different CLK openers which you will find listed below.

Corel R.A.V.E. Animation

These CLK files contain the animated logos and navigation controls created in Corel R.A.V.E, an animation software. You can create frame-by-frame animations, tweened animations, and step transition animations.

CLK opener for Windows

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

WatchGuard Cloaked File

WatchGuard cloaked files are special attachments created by WatchGuard security products (such as Fireware's Gateway AntiVirus or Data Loss Prevention) to secure or quarantine email attachments that violate policy. The cloaking process renames the forbidden attachment so that it ends with an extra extension ".clk" and replaces the usual content with metadata and cryptic content. These files are intended to prevent unauthorized access until they are reviewed or unlocked through a trusted utility.

These files are produced automatically in email security workflows: when WatchGuard's Gateway AntiVirus or DLP detects a suspicious attachment in an email, it does not send that attachment in its original form. Instead, the attachment is stored in a cloaked form and renamed to have the ".clk" extension appended to the original name. The WatchGuard System Manager software supplies a program (unlock.exe) that takes the cloaked file and restores the original attachment when permitted, making it possible to open it with the appropriate application.

Internally, cloaked files begin with a clear ASCII header: "This file has been cloaked. The original message may be retrieved by" at file start (offset zero). After this header, the rest of the file contains encrypted or obfuscated content replacing the original attachment.

Various apps that use files with this extension

These apps are known to open certain types of CLK files. Remember, different programs may use CLK files for different purposes, so you may need to try out a few of them to be able to open your specific file.

Help us help others

File.org helps thousands of users every day, and we would love to hear from you if you have additional information about CLK file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.