What Is a DYLIB File?

Mach-O Dynamic Library Files Explained

What to Know

  • A DYLIB file is a Mach-O dynamic library file you can open with Xcode.
  • Analogous to Windows DLLs, DYLIBs are used in macOS.

This article explains what a DYLIB file is and how to open one.

What Is a DYLIB File?

A file with the DYLIB file extension is a Mach-O (Mach Object) dynamic library file that an application references during runtime to perform certain functions on an as-needed basis. The format has replaced the older A.OUT file format.

Mach-O is a file format that's used for various types of files including object code, shared libraries, core dumps, and executable files, so they might contain general data that multiple applications reuse over time.

DYLIB files are normally seen saved with other Mach-O files like .BUNDLE and .O files, or even alongside files that are without a file extension. The libz.dylib file is a common DYLIB file that's the dynamic library for the zlib compression library.

DYLIB files in macOS High Sierra

How to Open a DYLIB File

DYLIB files generally don't need to be opened because of the nature of how they're used.

However, you should be able to open one with Apple's Xcode, either through a menu or by just dragging the file directly into the program. If you can't drag it, it's possible you may need to first make a Frameworks folder in your project that you can put the DYLIB file info.

Most DYLIB files are probably dynamic library files, but if you suspect that yours isn't and that it's instead used by a different program for a different purpose, try opening the file in a free text editor. If your specific file isn't a dynamic library file, then being able to see the contents of the file as a text document may shed some light on the type of format the file is in, which may help you determine what program should be used to open that particular file.

How to Convert a DYLIB File

While there are many free file converters that exist for the sole purpose of converting one file format to another in order to use the file in a different program or for a different purpose, there isn't any reason to use one on a DYLIB file.

There are lots of file types that shouldn't be converted to any other format because doing so wouldn't be beneficial. In this case, having the file in a different format would change its file extension, which would make any applications dependent on it to be without the DYLIB's functionality.

A true format conversion would also change the contents of the file, which, again, would disrupt any application that needs it.

Still Can't Open It?

If your file doesn't open with Xcode and a text editor was unhelpful, you might not be dealing with this file format at all. This can happen by mistake if you've misread the file extension and confused another file for one that uses the DYLIB file extension.

DYC is one example of a file extension that might at first glance appear to be related to DYLIB files. These are actually driver files used by some Xerox printers, so you can't open one with the programs mentioned above.

Similar is the LIB file extension used for library files by some software. If that's what you have, you'll need a different program on your computer before you can open/edit it.

More Information on DYLIB Files

Although they're similar to DLL files in the Windows operating system, DYLIB files are only used on, and therefore usually only seen on, operating systems that are based on the Mach kernel, like macOS and iOS.

Apple's Documentation Archive has a lot more information on dynamic library programming, including how libraries are loaded when an app starts up, how dynamic libraries differ from static libraries, and guidelines and examples on creating dynamic libraries.

  • Where do DYLIB files go on a Mac?

    The standard locations for dynamic libraries are ~/lib, /usr/local/lib, and /usr/lib. Alternatively, you can place a DYLIB file at a nonstandard location in your file system provided you add that location to one of these environment variables:


  • How do you replace a DYLIB file?

    First, you must find a source to download the replacement file. Next, delete the original file in the application package. Finally, paste the downloaded file with the same name to the location of the deleted original file.

  • How serious is DYLIB hijacking?

    DYLIB hijacking is an attack that attempts to load dynamic libraries from unsecured locations to gain control of a process. You can use a utility to scan your system for susceptible or hijacked applications. For example, you can download Dylib Hijack Scanner to scan for vulnerabilities.

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