diff --git a/Makefile.am b/Makefile.am
index 7d48b91a0..ff42180cc 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -630,6 +630,14 @@ compile_commands: $(abs_srcdir)/compile_commands.json
 browser/node_modules: browser/package.json browser/archived-packages
 	@cd browser && npm install
 
+eslint: browser/node_modules
+	browser/node_modules/.bin/eslint browser/src browser/js browser/admin/src \
+		--max-warnings 0 \
+		--resolve-plugins-relative-to browser \
+		--ignore-path browser/.eslintignore \
+		--no-eslintrc \
+		--config browser/.eslintrc
+
 install-exec-hook:
 	cd $(DESTDIR)$(bindir) && \
 	$(LN_S) coolconfig loolconfig && \
@@ -671,7 +679,7 @@ check-for-system-nss:
 		fi \
 	fi
 
-check: check-for-system-nss check-recursive
+check: check-for-system-nss check-recursive eslint
 	$(GEN_COVERAGE_COMMAND)
 
 coverage-report:
diff --git a/browser/.eslintrc b/browser/.eslintrc
index fcaf8bb0f..f3e275b85 100644
--- a/browser/.eslintrc
+++ b/browser/.eslintrc
@@ -20,7 +20,11 @@
     "no-control-regex": 0,
     "no-useless-escape": 0,
     "semi": 2,
-    "no-redeclare": 0
+    "no-redeclare": 0,
+    /// Rules that are set to warn will fail in CI but not when building for development:
+    "no-debugger": 1,
+    "no-unreachable": 1,
+    "no-unused-vars": 1,
   },
   "globals": {
     "L": true,