Instructions for Building the Zotero Client assume a POSIX-compliant system capable of handling symbolic links. These instructions will work out-of-the box on most Linux and macOS systems, but Windows requires a few extra steps.

1. Install Node.JS (a 64-bit release of Node 16 LTS recommended) and Cygwin. During Cygwin setup, in the “Select Packages” step, select the following additional packages to install: “git”, “p7zip”, “python27”, “python3”, “wget”, “zip” and “unzip”.
2. Run Cygwin Terminal as Administrator (right click → Run as Administrator). Run the following commands in that Cygwin terminal, in a single session.
3. Force Cygwin to use native windows symlinks:

   export CYGWIN="winsymlinks:nativestrict"

4. Clone the Zotero source code, Zotero XPI build scripts, and standalone client build scripts. Zotero source code is cloned but not checked out (i.e. no actual files are created):

   git clone --config core.symlinks=true --no-checkout https://github.com/zotero/zotero zotero-client
   git clone --recursive https://github.com/zotero/zotero-build
   git clone --recursive https://github.com/zotero/zotero-standalone-build

5. Change to the source code repo, check out required files, and install Node.js modules:

   cd zotero-client
   git checkout HEAD package.json package-lock.json
   npm install

6. Check out the remaining files, creating valid symbolic links:

   git checkout -f HEAD
   git submodule update --init --recursive

   Note: If you are seeing here errors of the form “error: unable to create symlink […]: Operation not permitted” then you are not running Cygwin as an administrator (see step 2 above).

7. Fetch “rcedit” (in zotero-standalone-build) which is an additional build dependency on Windows:

    (cd ../zotero-standalone-build && ./scripts/fetch_rcedit)

8. Now continue with instructions on Building the Zotero Client, beginning with step 3.

This error is caused by the Cygwin shell misinterpreting Windows line endings in the Node executable. Rerun the Cygwin installer, add the “dos2unix” package, then run:

dos2unix "$(which npm)" "$(which npx)"