ERROR_MRM_FILEPATH_TOO_LONG - 15121 (0x3B11)
Filepath too long.
Updated: Feb 21, 2026
Technical Meaning
The error code ERROR_MRM_FILEPATH_TOO_LONG indicates that a file path provided to an API function exceeds the maximum allowable length. This is a specific technical mechanism designed to prevent system instability and ensure proper operation of file system operations.
Error Details
This error typically occurs when attempting to access or manipulate a file or directory whose path length surpasses the limit enforced by the Windows operating system. The maximum path length allowed in Windows, including drive letter, backslashes, and null characters, is 32,767 characters. However, certain operations may have stricter limits.
Usage Context
This error can be encountered during various file system operations such as creating files or directories, opening existing ones, or performing any operation that requires a path string. It is particularly relevant for applications that handle long filenames or paths, including those involving network shares and symbolic links.
Developer Interpretation
Developers should ensure that the paths used in their applications do not exceed the maximum allowed length to avoid encountering this error. This can be achieved by using shorter names where possible, breaking down long paths into multiple operations, or utilizing alternative methods such as UNC paths for networked resources.
Related Errors
These errors may occur in similar contexts and can provide additional context when troubleshooting path-related issues.
FAQ
Q: What is the maximum allowed path length in Windows?
A: The maximum path length, including drive letter, backslashes, and null characters, is 32,767 characters. However, certain operations may have stricter limits.
Q: Can this error occur on all file system operations?
A: This error typically occurs during operations that require a path string, such as creating or opening files/directories. It does not apply to all file system operations.
Summary
The ERROR_MRM_FILEPATH_TOO_LONG (15121) indicates that the provided file path exceeds the maximum allowable length in Windows. Developers should ensure their applications handle paths within these limits to avoid encountering this error and maintain system stability.