Licenses

The open-source work inside FileConcat.

FileConcat is open source under the MIT license. The readers that open PDFs, Office files and archives in your browser are built from other projects, and their licenses travel with them. Every library and its full license text is listed in third-party-notices.txt. This page covers what that list cannot.

7-Zip, for 7z, RAR, bz2 and xz.

Archives other than ZIP and TAR are opened by 7-Zip 24.09 by Igor Pavlov, compiled to WebAssembly by the 7z-wasm project. 7-Zip is licensed under the GNU Lesser General Public License, version 2.1 or later. A few of its files are under BSD licenses, and its RAR decoder also carries the unRAR license restriction below.

The source code for the exact build we ship, served from this site: 7z2409-src.tar.xz (7-Zip 24.09, sha256 49c05169...6133a) and 7z-wasm-1.2.0-build.tar.gz, the patch and build scripts that turn it into WebAssembly. The same files are upstream at ip7z/7zip 24.09 and use-strict/7z-wasm v1.2.0. We made no changes of our own.

7-Zip runs as its own file, 7zz.wasm, separate from FileConcat's code. You may replace it with a build of your own: build 7z-wasm from the source above and run FileConcat from its repository with your file in place of the one in the 7z-wasm package.

The decompression engine for RAR archives was developed using source code of unRAR program. All copyrights to original unRAR code are owned by Alexander Roshal. The unRAR sources cannot be used to re-create the RAR compression algorithm, which is proprietary. Distribution of modified unRAR sources in separate form or as a part of other software is permitted, provided that it is clearly stated in the documentation and source comments that the code may not be used to develop a RAR (WinRAR) compatible archiver.

The PDF reader.

PDFs are read by LiteParse from LlamaIndex (Apache 2.0), which is built on PDFium. It includes resvg and usvg 0.44.0 under the Mozilla Public License 2.0, unmodified; their source is at linebender/resvg v0.44.0.

This software is based in part on the work of the Independent JPEG Group.

Everything else.

Office files are read by anydoc from Firecrawl (MIT), and the rest of the app uses npm packages under permissive licenses. All of them, with their license texts, are in the notices file, which is rebuilt from the shipped code on every release.

Read the full notices

Last updated October 5, 2026