How to Identify a File Type Without or With the Wrong Extension

Sometimes, you may encounter files that either lack an extension or have an incorrect one. Identifying the type of such files is useful, especially if you need to process the data effectively. Below are several methods to help you determine the file type even when there’s no extension.

1. Using the file Command in UNIX-Based Systems

If you're using Linux, macOS, or another UNIX-based operating system, the file command is a helpful tool for identifying file types. This command analyzes a file’s contents to reveal its type.

file filename

The output will show the file type based on its actual contents rather than its extension.

2. Using PowerShell in Windows

Windows users can use PowerShell to determine the file type. Open PowerShell and run the following command:

Get-FileHash -Algorithm SHA256 filename | Format-List

This command calculates the file’s hash, which can sometimes provide insight into the file structure. However, for more detailed results, a specialized tool may be more effective.

3. Checking with a Text Editor

Some text editors, like Notepad++ or Visual Studio Code, may provide clues about a file’s type when opened. For instance, if the file contains readable headers or data characteristic of specific formats (such as PDF or JPEG), you might be able to visually identify the type.

4. Using Online Services

Several online tools, such as CheckFileType, allow you to upload a file and identify its type. These services analyze the file’s data and provide information about its format.

5. Specialized Software and Utilities

For deeper analysis, you can use tools like TrID. TrID analyzes the "signatures" of files to determine their types and supports a large number of formats. This tool is free to use.

6. Opening in a HEX Editor

HEX editors, like HxD, display the file’s byte and hexadecimal values. Many files have distinctive signature bytes in the first few lines that indicate their type (e.g., FF D8 FF for JPEG files).