.CWW file extension
To open .CWW files on Windows, determine the source: if it’s from a crossword/puzzle context, install and open it with Crossword Weaver; if it’s from a wood/structural engineering workflow, open it within the relevant WoodWorks application (e.g., Sizer or Shearwalls).
To open a .CWW file, use the app that created it: Crossword Weaver (for crossword puzzles) or WoodWorks software (for WoodWorks binary databases). If you are unsure which type you have, check where it came from (puzzle vs. engineering/wood design workflow) and try the relevant desktop program—mobile OSes typically won’t open it directly.
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 .CWW files
Use these platform-specific instructions to open .CWW files safely.
Windows
- Determine the source: if it’s from a crossword/puzzle context, install and open it with Crossword Weaver; if it’s from a wood/structural engineering workflow, open it within the relevant WoodWorks application (e.g., Sizer or Shearwalls).
- In File Explorer, right-click the .CWW file → Open with → Choose another app, then select the appropriate program.
- If the file is a WoodWorks database, use the WoodWorks product’s database features/workflow (per WoodWorks help) rather than trying to import it into unrelated software.
Mac
- If you don’t have the creating application on macOS, plan to open the .CWW file on a Windows PC where Crossword Weaver or the relevant WoodWorks application is installed.
- If you do have a compatible desktop app available, Control-click the file → Open With → select the correct program.
Linux
- .CWW is typically opened with its creating desktop application; if you don’t have a native Linux version of the relevant software, transfer the file to a Windows machine with Crossword Weaver or the appropriate WoodWorks application.
- Avoid trying random converters—first confirm whether it is a Crossword Weaver puzzle file or a WoodWorks binary database.
iOS
- iOS generally won’t open .CWW natively; if the file came from Crossword Weaver or WoodWorks, transfer it to a desktop system with the corresponding software to view/use it.
Android
- Android typically has no standard app support for .CWW; if it’s a Crossword Weaver or WoodWorks file, move it to a desktop computer with the appropriate program to open it.
Security notes
- .CWW files are typically binary data; they are not meant to contain macros like office documents, but a malicious or malformed file can still exploit bugs in the program that parses it—only open files from sources you trust.
- Treat unexpected .CWW email attachments with caution, especially if you were not expecting a crossword puzzle or WoodWorks database file; confirm with the sender what software created it.
- Avoid renaming unknown files to .CWW (or renaming .CWW to another extension) to “make it open”—this can lead you to open the file with the wrong parser and increase the chance of errors or security issues.
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Can't open this file?
These are the most common causes and fixes when .CWW files fail to open.
Common reasons
- The .CWW file won’t open (wrong program)
- Windows asks “How do you want to open this file?”
- File appears corrupted or incomplete
- Trying to edit a WoodWorks .CWW database directly
Fix steps
- Check where the file came from: Crossword Weaver puzzle vs. WoodWorks database (Sizer/Shearwalls workflow).
- Open it using the matching application (Crossword Weaver for puzzle files; the relevant WoodWorks software for database files).
OS-specific troubleshooting
What is a .CWW file?
.CWW can refer to at least two unrelated formats: (1) a Crossword Weaver puzzle file used by Variety Games Inc.’s Crossword Weaver, and (2) a WoodWorks binary database file used by WoodWorks applications (e.g., Sizer and Shearwalls) as part of their material/component database system. Because it is a binary format in both uses, it is generally not meant to be edited in a text editor.
Background
In consumer and hobby contexts, .CWW is associated with Crossword Weaver, a crossword creation/playing tool from Variety Games Inc. In that case, the file typically represents a crossword puzzle project or puzzle data saved by the program.
In professional structural/wood design workflows, WoodWorks documentation describes .cww as a binary WoodWorks database format used by WoodWorks applications (including the WoodWorks Sizer and Shearwalls products) alongside other related database extensions. These databases support the applications’ internal material/component data needs rather than being a document intended for general interchange.
The extension is also registered as an IANA media type (application/prs.cww). While a registered media type can help systems label the file, it does not guarantee broad OS-level support—practically, the creating application is still the key to opening it.
Common MIME types: application/prs.cww
Further reading
Authoritative resources for more details on the .CWW format.
Common .CWW issues
The .CWW file won’t open (wrong program)
The .CWW extension is used by different, unrelated formats. If you open it in the wrong application (or an OS-default app), it may fail or show as corrupted.
- Check where the file came from: Crossword Weaver puzzle vs. WoodWorks database (Sizer/Shearwalls workflow).
- Open it using the matching application (Crossword Weaver for puzzle files; the relevant WoodWorks software for database files).
Windows asks “How do you want to open this file?”
No application is currently associated with .CWW on your system, or the required software is not installed.
- Install the correct software for your .CWW type (Crossword Weaver or the applicable WoodWorks program).
- Use Right-click → Open with to pick the installed program and optionally set it as the default.
File appears corrupted or incomplete
Binary data files can fail to open if truncated during download/copy, or if created by a newer/older version that isn’t compatible with your installed software.
- Re-copy or re-download the file from the original source (avoid email clients or cloud sync conflicts if possible).
- Try opening it with the same product and version family that created it (e.g., the corresponding WoodWorks application, or Crossword Weaver).
Trying to edit a WoodWorks .CWW database directly
WoodWorks documentation describes .cww as a binary database format, which is not intended for manual editing and may be locked to the application’s database management process.
- Use the WoodWorks application’s supported database workflow (per WoodWorks help) rather than editing the file in a text or hex editor.
- If you need to change materials/components, make the changes through the WoodWorks software features designed for database management.
FAQ
What program opens .CWW files?
Most commonly, either Crossword Weaver (for crossword puzzle files) or WoodWorks software (for WoodWorks binary database files used by products like Sizer and Shearwalls). The correct program depends on where the file came from.
Is .CWW the same thing everywhere?
No. The same .CWW extension is used for different file types (at least Crossword Weaver puzzles and WoodWorks binary databases). You must match the file to the creating application.
Can I convert a .CWW file by renaming the extension?
No. Renaming only changes the filename, not the underlying format. Use the original program’s export/save-as features if you need another format.
Is there an official MIME type for .CWW?
Yes. IANA lists a registered media type: application/prs.cww. This helps with identification but does not guarantee that your OS has a built-in viewer.
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