BLL File

What are BLL files and how to open them

Are you having problems opening a BLL 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 BLL files.

What is a BLL file?

A .BLL file is a Borland Language Library file.

The Borland Language Library format is used by Borland C++ under OS/2 to store international locale data that supports the C run-time's setlocale API. It holds data that describe how to format numbers, dates, times, currency; how to sort text; how to classify characters by alphabetic, numeric, upper/lower, etc. The "locale library" file contains code-page and cultural convention data needed when a program requests a locale other than the default "C" locale.

This library data is produced by the Borland C++ build or installer for OS/2 version 1.5, and is loaded at run time by the setlocale function. If setlocale is passed a non-default locale, the runtime searches for the file named LOCALE.BLL using several fallback locations: the application's executable directory, the current working directory, and directories listed in the LOCALEPATH environment variable. If LOCALE.BLL is not found, the locale change fails, leaving the previous locale unchanged.

Byte-signature information: the file begins with the ASCII string "LOCALE.BLL" at offset 0 (i.e. the first bytes are 0x4C 4F 43 41 4C 45 2E 42 4C 4C), which helps identify this locale library file uniquely.

How to open BLL files

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

While we have not verified the app ourselves yet, our users have suggested a single BLL opener which you will find listed below.

Last updated: August 24, 2026

Various apps that use files with this extension

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

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