C3PROJ File

What are C3PROJ files and how to open them

Are you having problems opening a C3PROJ 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 C3PROJ files.

What is a C3PROJ file?

A .C3PROJ file is a Construct 3 Project file.

Construct 3 project files store all the data needed to build a game, app or interactive media in Construct 3. Created by the Construct 3 editor, these files capture metadata such as the project name, author, version, website, display settings (viewport dimensions, fullscreen mode, letterboxing, etc.), and startup configuration like the first layout and whether a loader layout is used. They also include all in-project content: layouts, event sheets, object types, families, timelines, flowcharts, scripts (JavaScript or TypeScript), 3D models, palettes, resources like sounds, music, videos, fonts, icons, and general files.

These projects are produced either as single-file archives (extension .c3p) or as folder-based projects. In the folder-based form, the main project file named project.c3proj is stored at the root and works like an index, referring to subfolders that contain the various content files. Construct reads this main file to locate resources and ignore any files not referenced. In single-file mode, the folder structure is zipped and renamed with a .c3p extension.

The main project file is in JSON format. It lists all resource types and folder structure as arranged in the Project Bar in Construct 3. Resource files are also individual JSON files (or other standard formats like PNG for images, WebM for audio, WOFF for fonts), stored under subfolders matching their categories (layouts, eventSheets, scripts, etc.). Some UI state files (uistate.json) are present which affect only the editor interface and not the running project.

Internal identification is possible via byte signatures: files often begin at offset 0 with the ASCII string like "{ projectFormatVersion":1, "savedWithRelease":", and contain field names such as SAVEDWITHRELEASE, OBJECTTYPES, EVENTSHEETS, FAMILIES, LAYOUTS, FIRSTLAYOUT, VIEWPORTWIDTH, VIEWPORTHEIGHT, AUTHORWEBSITE, DESCRIPTION, USEDADDONS, among others.

How to open C3PROJ files

Important: Different programs may use files with the C3PROJ file extension for different purposes, so unless you are sure which format your C3PROJ file is, you may need to try a few different programs.

We have not yet verified any programs for Windows that work with this specific file format. If you know one, please use the 'Suggest a program' link below. Thanks!

Last updated: August 25, 2026

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