.BSP file extension

To open .BSP files on Windows, identify the originating engine/workflow (most commonly Source or GoldSrc). If it came from a Source mod/map compile, it is typically a Source compiled map.

To open a .BSP file, use the game engine/toolchain it was made for—most often Valve Source (compiled maps produced by VBSP) or the older GoldSrc BSP variant. If double-clicking doesn’t work, open it from within the game/modding tools rather than renaming the file extension.

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Last updated: April 29, 2026 · Reviewed by Julian Stricker

Open on your device

Choose your operating system for a dedicated step-by-step opening guide.

How to open .BSP files

Use these platform-specific instructions to open .BSP files safely.

Windows

Identify the originating engine/workflow (most commonly Source or GoldSrc). If it came from a Source mod/map compile, it is typically a Source compiled map.
Open it using the appropriate Valve game/toolchain for that engine (for Source maps, use the Source game or Source SDK tools associated with the map).
If it still won’t open, confirm the file version/variant (Source vs GoldSrc) and try opening it with tools meant for that specific BSP type rather than a generic viewer.

Full Windows guide

Mac

Determine whether the .BSP is a Source or GoldSrc compiled map (they differ and require different compatible tools).
Use the corresponding Valve game/tools on macOS (where available) to load the map; BSPs are typically loaded by the engine rather than “opened” like a document.
If it fails to load, the file may be for a different engine branch/version; verify it matches the game/tool version it was built for.

Full Mac guide

Linux

Check whether the .BSP is a Valve compiled map for Source/GoldSrc and which variant it is.
Open/load the map using the appropriate Valve game/tools on Linux (where available) instead of trying to preview it in a general-purpose app.
If it doesn’t load, the BSP may be corrupted or built for a different engine/version; re-obtain it from the original source or recompile from the original map sources if you have them.

Full Linux guide

iOS

iOS does not commonly support opening Valve .BSP compiled maps directly; transfer the file to a desktop (Windows/macOS/Linux) with the appropriate game/tools to load or inspect it.

Full iOS guide

Android

Android does not commonly support opening Valve .BSP compiled maps directly; transfer the file to a desktop (Windows/macOS/Linux) with the appropriate game/tools to load or inspect it.

Full Android guide

Security notes

Treat .BSP files from unknown sources as untrusted: they are complex binary formats parsed by games/tools, and malformed files can trigger crashes or vulnerabilities in parsers.
Prefer opening untrusted maps in a controlled environment (e.g., a non-admin user account) and avoid mixing unknown BSPs into valuable mod/game installations.
If a BSP arrives together with other files (mods, installers, scripts), be cautious with the bundle; the BSP itself is map data, but the surrounding content may include executable components.

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Can't open this file?

These are the most common causes and fixes when .BSP files fail to open.

Common reasons

The .BSP file won’t open or won’t load in-game
File association error (double-click opens the wrong app)
Corrupted or incomplete download

Fix steps

Confirm whether it is a Source BSP or a GoldSrc (BSP30) file and use tools intended for that specific format.
Try loading it with the exact game/toolchain it was built for (engine/version mismatches are common).

OS-specific troubleshooting

What is a .BSP file?

.BSP (in the Valve context) is a compiled map data format loaded by the engine at runtime. Source BSPs store content in a header/version plus multiple data “lumps” (separate blocks for geometry, visibility, entities, etc.). In Source workflows, VBSP compiles an editable map (commonly .VMF) into a runnable .BSP for the game to load.

Background

In Valve’s Source engine pipeline, a map author edits a source map (commonly a .VMF) and then compiles it into a .BSP using the VBSP tool. The resulting .BSP is the compiled, engine-ready map file that the game can load.

Technically, Source BSP files are structured around a header/version and a set of “lumps,” which store different categories of map data. This design lets the engine and tools locate specific data blocks without scanning the whole file.

There is also a closely related older Valve/Quake-derived variant used by GoldSrc (often referred to as BSP30). While both are called “BSP,” they are not necessarily interchangeable; tools and games generally expect the specific BSP variant for that engine generation.

Common MIME types: model/vnd.valve.source.compiled-map

Common .BSP issues

The .BSP file won’t open or won’t load in-game

This often happens when the BSP is for a different engine branch/version (Source vs GoldSrc), or the game/tools don’t recognize the file’s version/lump layout.

Confirm whether it is a Source BSP or a GoldSrc (BSP30) file and use tools intended for that specific format.
Try loading it with the exact game/toolchain it was built for (engine/version mismatches are common).

File association error (double-click opens the wrong app)

Desktop environments may not know what to do with .BSP and may pick an unrelated program.

Open the map from within the appropriate game/modding tools instead of double-clicking.
If needed, change the file association to the relevant application on your system.

Corrupted or incomplete download

Because BSPs contain many structured “lumps,” truncated files can fail to load or crash tools that expect valid lump offsets/sizes.

Re-download or re-copy the file from the original source and verify the transfer completed.
If you have the original editable map sources, recompile the map (for Source: compile with VBSP as part of the normal compile process).

FAQ

What does .BSP usually mean?

Most commonly, .BSP refers to Valve compiled map files for the Source engine (and a related older GoldSrc variant). These are game levels compiled into a format the engine can load.

Can I convert a .VMF to .BSP by renaming it?

No. In Source workflows, the .BSP is produced by compilation (VBSP compiles an editable map into a BSP). Renaming does not compile or transform the data.

Why does my tool say the BSP version is unsupported?

There are multiple BSP variants and versions (notably Source vs GoldSrc/BSP30). Use tools intended for the correct engine family and, ideally, the specific game/version the BSP targets.

Is there an official MIME type for Source .BSP maps?

Yes. IANA lists the vendor media type model/vnd.valve.source.compiled-map, commonly associated with Source engine compiled BSP maps.

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