.CSP file extension
To open .CSP files on Windows, if you know the file is from CommonSpace: install/open CommonSpace (Sixth Floor Media) and open the .csp file from within the application.
To open a .CSP file, use CommonSpace (by Sixth Floor Media) or another tool that recognizes the MIME type application/vnd.commonspace. If you don’t know where the file came from, first confirm whether it is a CommonSpace file, since “.csp” can also mean other formats (for example, Concept Server Page).
Last updated: April 30, 2026 · Reviewed by Julian Stricker
Open on your device
Choose your operating system for a dedicated step-by-step opening guide.
How to open .CSP files
Use these platform-specific instructions to open .CSP files safely.
Windows
- If you know the file is from CommonSpace: install/open CommonSpace (Sixth Floor Media) and open the .csp file from within the application.
- If you are unsure what it is: right-click the file → Properties, and check what program Windows suggests; if it’s unknown, ask the sender what created it before trying random apps.
Mac
- If it is a CommonSpace file: open it using the CommonSpace application (if available to you) via File → Open.
- If macOS can’t identify it: Control-click → Open With → choose the correct app (do not rename the extension to force an open).
Linux
- Use a MIME-aware file identification tool (or your desktop’s file properties) to see whether it is detected as application/vnd.commonspace; shared-mime-info is commonly used for these associations.
- If it is application/vnd.commonspace: open it with the appropriate CommonSpace-compatible software available in your environment, or transfer it to a system where CommonSpace is installed.
iOS
- iOS typically will not open CommonSpace binary .csp files directly; use the Files app to share/transfer the file to a desktop system with the correct software (or ask the sender to export to a more common format).
Android
- Android typically will not open CommonSpace binary .csp files directly; transfer the file to a desktop system with the appropriate software, or request an export in a standard format from the creator.
Security notes
- Treat .csp files as opaque binary data: only open them if you trust the source and you know the intended application (especially because the extension is ambiguous).
- Avoid changing associations to open a .csp in a text editor or browser if you expected a CommonSpace file; if it is actually a server-page/script-type .csp from a web context, it may contain code or sensitive server-side content.
- Be cautious with “file sniffing” utilities or untrusted third-party converters: malformed binary files can trigger parser bugs; prefer the original creating application (CommonSpace) or well-known identification tools.
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Can't open this file?
These are the most common causes and fixes when .CSP files fail to open.
Common reasons
- The .CSP file opens in the wrong app (or shows as a web/script file)
- No application can open the .CSP file
- File type detection is inconsistent across computers
- The .CSP file seems corrupted or incomplete
Fix steps
- Confirm the file’s origin (ask the sender what application produced it).
- Check whether it matches application/vnd.commonspace (CommonSpace) instead of a web-related CSP format, then set the default app accordingly.
OS-specific troubleshooting
What is a .CSP file?
A CommonSpace .CSP file is a binary data file associated with the IANA-registered media type application/vnd.commonspace, and the registered filename extensions include .csp (and .cst). Operating systems and desktop environments may associate .csp with this MIME type via shared MIME databases, but the extension alone is not a guarantee because .csp is used by multiple, unrelated formats.
Background
.CSP is an extension officially associated (via IANA media type registration) with CommonSpace files, which are described as binary and created by CommonSpace (Sixth Floor Media). In practice, this typically means the file is meant to be opened inside the CommonSpace workflow rather than treated as a generic document.
However, “.csp” is also commonly cited in web contexts as “Concept Server Page,” which is a different meaning and not the same as CommonSpace’s binary data files. This ambiguity is a frequent source of confusion: two files can share the same extension but require completely different software.
On Linux and other freedesktop.org-based desktops, file associations may be handled by the shared-mime-info system (MIME types and filename globs). Tools that identify files by MIME type (rather than just extension) can help you confirm whether a given .csp is actually application/vnd.commonspace.
Common MIME types: application/vnd.commonspace
Further reading
Authoritative resources for more details on the .CSP format.
Common .CSP issues
The .CSP file opens in the wrong app (or shows as a web/script file)
Because .csp is used by multiple, unrelated formats, your system may associate it with the wrong program or treat it like a different “.csp” type (for example, a web/server page format).
- Confirm the file’s origin (ask the sender what application produced it).
- Check whether it matches application/vnd.commonspace (CommonSpace) instead of a web-related CSP format, then set the default app accordingly.
No application can open the .CSP file
If the file is a CommonSpace binary, you generally need CommonSpace (Sixth Floor Media) or a compatible tool; many devices and apps won’t support it.
- Install/use the creating application (CommonSpace) on a desktop system and open the file from within that application.
- If you don’t have access to CommonSpace, request the sender to export or provide the content in a more widely supported format.
File type detection is inconsistent across computers
Different systems may rely on different MIME databases or heuristics; desktop environments commonly use shared-mime-info rules to map extensions to MIME types, but this can vary by installation.
- On Linux desktops, ensure MIME associations are up to date via your distribution’s shared-mime-info updates.
- Use a MIME-aware identification tool to verify the file is application/vnd.commonspace before troubleshooting app associations.
The .CSP file seems corrupted or incomplete
Binary data files are sensitive to truncation or transfer errors; an incomplete download or email gateway modification can make them unreadable.
- Re-download or re-copy the file from the original source (avoid copy/paste through chat systems that may alter files).
- Ask for the file to be re-sent in a lossless way (for example, as a direct attachment or via a trusted file transfer) and try opening again in the creating application.
FAQ
What program opens a .CSP file?
For the IANA-registered CommonSpace format (application/vnd.commonspace), the creating application is CommonSpace by Sixth Floor Media. If your .csp came from a web context, it may instead be a different format (such as Concept Server Page) and would not open in CommonSpace.
How can I tell if my .CSP is a CommonSpace file?
The most reliable method is to confirm the source application (ask the sender) or use MIME-aware identification that recognizes application/vnd.commonspace. The .csp extension alone is not definitive because it is used by multiple formats.
Can I open CommonSpace .CSP files on iPhone/Android?
Typically no—mobile platforms usually do not have common support for CommonSpace binary .csp files. Transfer the file to a desktop system with the correct application, or request an export to a more common format.
Should I rename .CSP to another extension to open it?
No. Renaming does not convert the file and often makes identification harder—especially for ambiguous extensions like .csp. Use the correct application or request an export from the creator.
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