diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 499685e38..0c11e626e 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -566,3 +566,28 @@ jobs:
       - name: test
         run: |
           make test
+
+  amalgam:
+    strategy:
+      matrix:
+        # TODO(bnoordhuis) test on windows
+        config:
+          - { os: ubuntu-latest }
+          - { os: macos-latest }
+    runs-on: ${{ matrix.config.os }}
+    steps:
+      - uses: actions/checkout@v4
+      - name: build
+        run: |
+          make
+      - name: create amalgamation
+        run: |
+          build/qjs amalgam.js $RUNNER_TEMP/quickjs-amalgam.c
+      - name: build amalgamation
+        run: |
+          cc -Wall -I. -o $RUNNER_TEMP/run-test262.o -c run-test262.c
+          cc -Wall -I/ -DQJS_BUILD_LIBC -o $RUNNER_TEMP/quickjs-amalgam.o -c $RUNNER_TEMP/quickjs-amalgam.c
+          cc -o $RUNNER_TEMP/run-test262 $RUNNER_TEMP/run-test262.o $RUNNER_TEMP/quickjs-amalgam.o -lm
+      - name: test
+        run: |
+          make test RUN262=$RUNNER_TEMP/run-test262
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 4028c1d44..8c60216f1 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -50,11 +50,20 @@ jobs:
           cd build
           cmake -DCMAKE_OSX_ARCHITECTURES="x86_64;arm64" ..
           make -j$(getconf _NPROCESSORS_ONLN)
+          (cd .. && build/qjs amalgam.js build/quickjs-amalgam.c)
+          cp ../quickjs.h .
+          zip -9 quickjs-amalgam.zip quickjs-amalgam.c quickjs.h
           mv qjs qjs-darwin
           mv qjsc qjsc-darwin
       - name: check
         run: |
           lipo -info build/qjs-darwin build/qjsc-darwin
+      - name: upload amalgamation
+        uses: actions/upload-artifact@v4
+        with:
+          name: quickjs-amalgam.zip
+          path: build/quickjs-amalgam.zip
+          compression-level: 0 # already compressed
       - name: upload
         uses: actions/upload-artifact@v4
         with:
@@ -124,7 +133,7 @@ jobs:
       - name: get assets
         uses: actions/download-artifact@v4
         with:
-          pattern: qjs-*
+          pattern: *
           path: build
           merge-multiple: true
       - run: ls -R build
diff --git a/amalgam.js b/amalgam.js
new file mode 100644
index 000000000..bc082dced
--- /dev/null
+++ b/amalgam.js
@@ -0,0 +1,46 @@
+import {loadFile, writeFile} from "qjs:std"
+
+const cutils_c = loadFile("cutils.c")
+const cutils_h = loadFile("cutils.h")
+const libbf_c = loadFile("libbf.c")
+const libbf_h = loadFile("libbf.h")
+const libregexp_c = loadFile("libregexp.c")
+const libregexp_h = loadFile("libregexp.h")
+const libregexp_opcode_h = loadFile("libregexp-opcode.h")
+const libunicode_c = loadFile("libunicode.c")
+const libunicode_h = loadFile("libunicode.h")
+const libunicode_table_h = loadFile("libunicode-table.h")
+const list_h = loadFile("list.h")
+const quickjs_atom_h = loadFile("quickjs-atom.h")
+const quickjs_c = loadFile("quickjs.c")
+const quickjs_c_atomics_h = loadFile("quickjs-c-atomics.h")
+const quickjs_h = loadFile("quickjs.h")
+const quickjs_libc_c = loadFile("quickjs-libc.c")
+const quickjs_libc_h = loadFile("quickjs-libc.h")
+const quickjs_opcode_h = loadFile("quickjs-opcode.h")
+
+let source = "#if defined(QJS_BUILD_LIBC) && defined(__linux__) && !defined(_GNU_SOURCE)\n"
+           + "#define _GNU_SOURCE\n"
+           + "#endif\n"
+           + quickjs_c_atomics_h
+           + cutils_h
+           + list_h
+           + libbf_h
+           + libunicode_h // exports lre_is_id_start, used by libregexp.h
+           + libregexp_h
+           + libunicode_table_h
+           + quickjs_h
+           + quickjs_c
+           + cutils_c
+           + libbf_c
+           + libregexp_c
+           + libunicode_c
+           + "#ifdef QJS_BUILD_LIBC\n"
+           + quickjs_libc_h
+           + quickjs_libc_c
+           + "#endif // QJS_BUILD_LIBC\n"
+source = source.replace(/#include "quickjs-atom.h"/g, quickjs_atom_h)
+source = source.replace(/#include "quickjs-opcode.h"/g, quickjs_opcode_h)
+source = source.replace(/#include "libregexp-opcode.h"/g, libregexp_opcode_h)
+source = source.replace(/#include "[^"]+"/g, "")
+writeFile(execArgv[2] ?? "quickjs-amalgam.c", source)
diff --git a/quickjs-libc.c b/quickjs-libc.c
index 67d2597f0..832f4723a 100644
--- a/quickjs-libc.c
+++ b/quickjs-libc.c
@@ -94,7 +94,9 @@ extern char **environ;
 #include "list.h"
 #include "quickjs-libc.h"
 
+#ifndef MAX_SAFE_INTEGER // already defined in amalgamation builds
 #define MAX_SAFE_INTEGER (((int64_t) 1 << 53) - 1)
+#endif
 
 #ifndef QJS_NATIVE_MODULE_SUFFIX
 #ifdef _WIN32