diff --git a/background.ts b/background.ts
index df8d1b2c..c262fff8 100644
--- a/background.ts
+++ b/background.ts
@@ -47,12 +47,14 @@ async function onBeforeRequest(
   const tab = await browser.tabs.get(request.tabId);
   const sourceUrl = tab.url ? new URL(tab.url) : undefined;
 
+  const tabContainerName = (await browser.contextualIdentities.get(tab.cookieStoreId)).name;
+
   const interpreter = new Sval({
     ecmaVer: "latest",
     sourceType: "script",
     sandBox: true,
   });
-  interpreter.import({ url: new URL(request.url), sourceUrl });
+  interpreter.import({ url: new URL(request.url), sourceUrl, containerName: tabContainerName });
   interpreter.run(program);
 
   const info = toContainerInfo(interpreter.exports.end);
diff --git a/ui.html b/ui.html
index 31862682..40230da1 100644
--- a/ui.html
+++ b/ui.html
@@ -106,6 +106,7 @@ <h1>Container Script</h1>
 					<ul style="color: #34495e; line-height: 1.8; margin-bottom: 15px;">
 						<li><code>url</code> &mdash; the <a href="https://developer.mozilla.org/en-US/docs/Web/API/URL">URL</a> being navigated to.</li>
 						<li><code>sourceUrl</code> &mdash; the URL of the page that initiated the navigation (may be <code>undefined</code> for new tabs).</li>
+						<li><code>containerName</code> &mdash; the name of the current container of the tab (before the change).</li>
 					</ul>
 					<p>
 						The code is executed using <a href="https://github.com/Siubaak/sval">Sval</a> due to <a href="https://www.w3.org/TR/CSP/">CSP</a> restrictions.
diff --git a/ui.ts b/ui.ts
index de742a49..bbcb781e 100644
--- a/ui.ts
+++ b/ui.ts
@@ -21,6 +21,10 @@ async function main() {
     " * The URL of the page that initiated the navigation (may be undefined for new tabs)",
     " */",
     "declare const sourceUrl: URL | undefined",
+    "/**",
+    " * The name of the current container of the tab",
+    " */",
+    "declare const containerName: string | undefined",    
   ].join("\n");
   const libUri = "ts:filename/ContainerScript.d.ts";
   monaco.languages.typescript.javascriptDefaults.addExtraLib(libSource, libUri);