diff --git a/.gitmodules b/.gitmodules
index 39e18fd..44fd2fc 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,3 +1,6 @@
 [submodule "backend/external/uwebsockets"]
 	path = backend/external/uwebsockets
 	url = https://github.com/uNetworking/uWebSockets.git
+[submodule "backend/external/json"]
+	path = backend/external/json
+	url = https://github.com/nlohmann/json.git
diff --git a/backend/CMakeLists.txt b/backend/CMakeLists.txt
index 17b83d1..2fb2469 100644
--- a/backend/CMakeLists.txt
+++ b/backend/CMakeLists.txt
@@ -34,9 +34,10 @@ FetchContent_Declare(
 )
 FetchContent_MakeAvailable(tec.h)
 
-# https://json.nlohmann.me/integration/cmake/#fetchcontent
-FetchContent_Declare(nlohmann_json URL https://github.com/nlohmann/json/releases/download/v3.12.0/json.tar.xz)
-FetchContent_MakeAvailable(nlohmann_json)
+# nlohmann/json via git submodule (backend/external/json)
+set(JSON_BuildTests OFF CACHE INTERNAL "")
+set(JSON_Install OFF CACHE INTERNAL "")
+add_subdirectory(external/json)
 
 find_package(OpenSSL REQUIRED)
 find_package(ZLIB REQUIRED)
diff --git a/backend/external/json b/backend/external/json
new file mode 160000
index 0000000..55f9368
--- /dev/null
+++ b/backend/external/json
@@ -0,0 +1 @@
+Subproject commit 55f93686c01528224f448c19128836e7df245f72