freedomofpress · lsd-cat · Jun 30, 2026 · Jun 18, 2026 · Jun 18, 2026 · Jun 18, 2026
diff --git a/extension/Makefile b/extension/Makefile
@@ -2,7 +2,7 @@ DIST := ../dist
 OUT  := $(DIST)/webcat-extension.zip
 OUT_TEST  := $(DIST)/webcat-extension-test.zip
 
-INPUTS := manifest.json dist/bundle.js dist/hooks/content.js icons pages data
+INPUTS := manifest.json dist/bundle.js dist/hooks/content.js icons pages data _locales
 FIXED_MTIME := 198001010000
 
 all: package package-test

diff --git a/extension/_locales/en/messages.json b/extension/_locales/en/messages.json
@@ -0,0 +1,23 @@
+{
+  "advanced": {
+    "message": "Advanced"
+  },
+  "hideAdvanced": {
+    "message": "Hide advanced"
+  },
+  "thisSite": {
+    "message": "this site"
+  },
+  "webcatVerificationSuccessful": {
+    "message": "WEBCAT verification successful"
+  },
+  "webcatVerificationFailed": {
+    "message": "WEBCAT verification failed"
+  },
+  "webcatIsRunning": {
+    "message": "WEBCAT is running"
+  },
+  "webcatIsUnavailable": {
+    "message": "WEBCAT unavailable on this site."
+  }
+}
diff --git a/extension/_locales/fi/messages.json b/extension/_locales/fi/messages.json
@@ -0,0 +1,47 @@
+{
+  "warningSecurityRisk": {
+    "message": "Varoitus: Tietoturvariski"
+  },
+  "didNotVerify": {
+    "message": "Ei varmennettu"
+  },
+  "errorShortDesc": {
+    "message": "WEBCAT ei voinut varmentaa, että koodi, jonka $1 tarjoili, vastaa allekirjoitettua manifestia, joten sivu estettiin."
+  },
+  "thisSite": {
+    "message": "tämä sivusto"
+  },
+  "advanced": {
+    "message": "Lisätietoja"
+  },
+  "hideAdvanced": {
+    "message": "Piilota lisätiedot"
+  },
+  "goBack": {
+    "message": "Palaa takaisin"
+  },
+  "whatYouCanDo": {
+    "message": "Ongelma johtuu sivustosta, ei verkkoyhteydestäsi. Koodi tai ympäristö, jonka sivusto tarjoili, ei vastaa sen kehittäjien kryptografista allekirjoitusta, joten WEBCAT esti sivun pitääkseen sinut turvassa. Voit ilmoittaa ongelmasta sivuston omistajalle, tai jos luulet tämän olevan bugi, raportoida sen $1."
+  },
+  "webcatRepository": {
+    "message": "WEBCATin tietovarastoon"
+  },
+  "file": {
+    "message": "Tiedosto: $1"
+  },
+  "errorCode": {
+    "message": "Virhekoodi: $1"
+  },
+  "webcatVerificationSuccessful": {
+    "message": "WEBCAT-varmennus onnistui"
+  },
+  "webcatVerificationFailed": {
+    "message": "WEBCAT-varmennus epäonnistui"
+  },
+  "webcatIsRunning": {
+    "message": "WEBCAT on käynnissä"
+  },
+  "webcatIsUnavailable": {
+    "message": "WEBCAT ei käytettävissä tällä sivustolla."
+  }
+}
diff --git a/extension/manifest.json b/extension/manifest.json
@@ -47,6 +47,7 @@
       "48": "icons/light/webcat.SVG",
       "128": "icons/light/webcat.SVG"
     },
-    "default_title": "WEBCAT unavailable on this site."
-  }
+    "default_title": "__MSG_webcatIsUnavailable__"
+  },
+  "default_locale": "en"
 }
diff --git a/extension/pages/error.html b/extension/pages/error.html
@@ -11,41 +11,58 @@
     <link rel="stylesheet" href="chrome://global/skin/aboutNetError.css" />
     <link rel="stylesheet" href="error.css" />
     <script src="error.js"></script>
-    <title>Warning: Security Risk</title>
+    <title data-i18n="warningSecurityRisk">Warning: Security Risk</title>
   </head>
   <body class="certerror webcaterror">
     <div class="container">
       <div id="text-container">
         <div class="title">
-          <h1 class="title-text">Did not verify</h1>
+          <h1 class="title-text" data-i18n="didNotVerify">Did not verify</h1>
         </div>
 
-        <p id="errorShortDesc">
+        <p id="errorShortDesc" data-i18n="errorShortDesc">
           WEBCAT could not verify that the code served by
-          <span id="error-host">this site</span> matches its signed manifest, so
-          the page was blocked.
+          <span id="error-host" data-i18n="thisSite">this site</span> matches
+          its signed manifest, so the page was blocked.
         </p>
 
         <div class="button-container">
-          <button id="advancedButton" aria-expanded="false">Advanced</button>
-          <button id="returnButton" class="primary">Go back</button>
+          <button
+            id="advancedButton"
+            aria-expanded="false"
+            data-i18n="advanced"
+          >
+            Advanced
+          </button>
+          <button id="returnButton" class="primary" data-i18n="goBack">
+            Go back
+          </button>
         </div>
 
         <div id="errorDebugInformation" hidden="">
-          <p id="whatCanYouDo">
+          <p id="whatCanYouDo" data-i18n="whatYouCanDo">
             The problem is with the site, not your connection. The code or the
             environment it served do not match what its developers
             cryptographically signed, so WEBCAT blocked the page to keep you
             safe. You can let the site owner know, or if you believe this is a
             bug open an issue in the
-            <a href="https://github.com/freedomofpress/webcat"
+            <a
+              href="https://github.com/freedomofpress/webcat"
+              data-i18n="webcatRepository"
               >WEBCAT repository</a
             >.
           </p>
-          <p class="error-detail" id="debug-file-line" hidden="">
+          <p
+            class="error-detail"
+            id="debug-file-line"
+            hidden=""
+            data-i18n="file"
+          >
             File: <span id="debug-file"></span>
           </p>
-          <p id="errorCode">Error code: <span id="debug-code"></span></p>
+          <p id="errorCode" data-i18n="errorCode">
+            Error code: <span id="debug-code"></span>
+          </p>
         </div>
       </div>
     </div>

diff --git a/extension/pages/error.js b/extension/pages/error.js
@@ -1,10 +1,28 @@
 document.addEventListener("DOMContentLoaded", () => {
+  function localize(container) {
+    container.querySelectorAll("[data-i18n]").forEach((el) => {
+      const substitutions = Array.from(el.children).map(
+        (child) => child.outerHTML,
+      );
+      const msg = browser.i18n.getMessage(
+        el.getAttribute("data-i18n"),
+        substitutions,
+      );
+      if (msg === "") {
+        return;
+      }
+      el.innerHTML = msg;
+      localize(el);
+    });
+  }
+  localize(document);
+
   const params = new URLSearchParams(location.hash.slice(1));
   const code = params.get("code") || "UNKNOWN";
   const host = params.get("host") || "";
   const file = params.get("file") || "";
 
-  setText("error-host", host || "this site");
+  setText("error-host", host || browser.i18n.getMessage("thisSite"));
   setText("debug-code", code);
 
   if (file) {
@@ -18,8 +36,8 @@ document.addEventListener("DOMContentLoaded", () => {
     advancedPanel.hidden = !advancedPanel.hidden;
     advancedButton.setAttribute("aria-expanded", String(!advancedPanel.hidden));
     advancedButton.textContent = advancedPanel.hidden
-      ? "Advanced"
-      : "Hide advanced";
+      ? browser.i18n.getMessage("advanced")
+      : browser.i18n.getMessage("hideAdvanced");
   });
 
   // The error page took a history slot

diff --git a/extension/src/webcat/ui.ts b/extension/src/webcat/ui.ts
@@ -19,7 +19,10 @@ export function setIcon(tabId: number) {
     tabId: tabId,
     path: `icons/${theme}/webcat.SVG`,
   });
-  browser.pageAction.setTitle({ tabId, title: "WEBCAT is running" });
+  browser.pageAction.setTitle({
+    tabId,
+    title: browser.i18n.getMessage("webcatIsRunning"),
+  });
 }
 
 export function setOKIcon(tabId: number, delegation?: string) {
@@ -43,7 +46,7 @@ export function setOKIcon(tabId: number, delegation?: string) {
     path: `icons/${theme}/webcat-ok.SVG`,
   });
 
-  let message = "WEBCAT verification successful";
+  let message = browser.i18n.getMessage("webcatVerificationSuccessful");
   if (delegation) {
     message += ` (${delegation})`;
   }
@@ -69,7 +72,7 @@ export function setErrorIcon(tabId: number) {
   });
   browser.pageAction.setTitle({
     tabId: tabId,
-    title: "WEBCAT verification failed",
+    title: browser.i18n.getMessage("webcatVerificationFailed"),
   });
 }