diff --git a/modules/home/browser.nix b/modules/home/browser.nix
index 0d21a4b..ed5c95f 100644
--- a/modules/home/browser.nix
+++ b/modules/home/browser.nix
@@ -80,6 +80,10 @@
         "network.protocol-handler.external.slack" = true;
         "network.protocol-handler.warn-external.slack" = false;
         "network.protocol-handler.prompt-without-user-activation" = false;
+      }
+      // lib.optionalAttrs (!config.isMacOS) {
+        # Remove Zen's margin around web content under Niri.
+        "zen.theme.content-element-separation" = 0;
       };
 
       extensions.packages = with inputs.firefox-addons.packages.${pkgs.stdenv.hostPlatform.system}; [