BLB File

What are BLB files and how to open them

Are you having problems opening a BLB 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 BLB files.

What is a BLB file?

BLB files have multiple uses, and ACT! Database Blob is one of them. Read more about the other uses further down the page.

ACT! Database Blob

ACT! Software (originally by Symantec) uses a file called the ACT! Binary Large Object Database as part of its data storage system. It stores items that don't fit into fixed-length tables - things like attachments, notes, email addresses, user names, drop-down list values, recurring-activity info, and settings. The main parts of the ACT! database refer out to this blob store rather than embedding all that data directly in tables.

The blob database is created and maintained by ACT! version 3.0 (and later). It works alongside other ACT! database files: tables in FoxPro format store core contact, activity, group, history, and relational data. When a user adds a note, attaches a file, or uses a drop-down list item, that variable-size data goes into the blob database. ACT! tables then store links or references pointing into that blob file so the program can fetch the correct content.

ACT! blob files begin with a specific ASCII signature at the very start: at file offset zero the bytes are "!@##@!Symantec--ACT!-3.0" followed by null bytes padding.

How to open BLB files

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

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

Last updated: August 24, 2026

All known file formats using extension .BLB

While ACT! Database Blob is a popular type of BLB-file, we know of 3 different uses of the .BLB file extension. Different software may use files with the same extension for different types of data.

Blob Sculptor For Windows Model

We know that one BLB format is Blob Sculptor For Windows Model. We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

Blorb Interactive Fiction Package

Blorb Interactive Fiction Package files bundle together an interactive fiction story (such as a Z-machine or Glulx executable) and its associated media resources (images, sounds, music, metadata) into a single archive, so that all parts needed to play the game can be shipped as one file. It was created by Andrew Plotkin for games using interpreters that support the Blorb format.

Games are produced (or "released") as Blorb files by IF authoring systems like Inform, or via tools like perlBlorb or BlorbTool, which read individual resource files plus optional story file and metadata, then wrap them into the Blorb standard. Interpreters supporting Blorb can read back those resources by resource number - displaying images, playing sounds, reading metadata - so the player sees cover art, narrative, sound effects etc., without needing separate files.

Internally the package is an IFF‐style ("Interchange File Format") container with top-level "FORM" chunk type "IFRS". The first chunk must be a resource index ("RIdx") listing each contained resource's ID, type and offset. Within the file are multiple chunks carrying resources in formats such as PNG or JPEG images, AIFF or Ogg Vorbis sound, MOD music, or the executable story file itself.

Technical signature: starts with ASCII "FORM" at offset 0, followed by bytes that encode the overall IFF length, then at offset 8 the ASCII string "IFRSRIdx" (denoting the IFRS FORM type followed immediately by the RIdx chunk)

Various apps that use files with this extension

These apps are known to open certain types of BLB files. Remember, different programs may use BLB 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 BLB file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.