OSB File

What are OSB files and how to open them

Are you having problems opening an OSB 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 OSB files.

What is an OSB file?

OSB files have multiple uses, and OpenStreetMap Binary Map Data is one of them. Read more about the other uses further down the page.

OpenStreetMap Binary Map Data

OpenStreetMap Binary Map Data files are a compact and efficient way for the editor Merkaartor to store OpenStreetMap vector map data in binary form instead of plain XML. They are designed for situations where users need faster loading, display, and editing of map regions without the overhead of human-readable text. Merkaartor creates them when you download map regions via its "World OSB Manager" feature, converting geographic features like nodes (points), ways (lines), and relations into binary structures for offline use and editing.

Inside a .OSB file is a complete picture of one or more map regions with all associated feature tags, geometries, and spatial metadata. These files are used internally by Merkaartor both to cache data you've downloaded from OpenStreetMap servers and to enable quicker re-rendering and interaction than if Merkaartor had to parse XML every time. Users typically work with .OSB files by opening them in Merkaartor for editing, viewing, or overlaying onto background imagery. Merkaartor does not use .OSB files the same way as the standard OpenStreetMap XML or PBF formats; it stores them in a proprietary binary layout intended specifically for its offline region management.

A technical signature begins the file with the ASCII string OSB at byte offset zero. Versioning is built in (e.g. via a 16-bit version number after the "OSB" header), followed by tables indexing tag keys and values, feature records for nodes, ways, and relations, and region/tile table-of-contents sections that enable Merkaartor to locate particular features efficiently.

How to open OSB files

We have identified one OSB opener that is compatible with this specific type of OSB file.

Programs that open OpenStreetMap Binary Map Data files

Last updated: August 10, 2026

All known file formats using extension .OSB

While OpenStreetMap Binary Map Data is a popular type of OSB-file, we know of 2 different uses of the .OSB file extension. Different software may use files with the same extension for different types of data.

Osu! Beatmap Storyboard Data

We know that one OSB format is Osu! Beatmap Storyboard Data. We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

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

Various apps that use files with this extension

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