diff --git a/manifest-chrome.partial.json b/manifest-chrome.partial.json
index 399004f..85ef12c 100644
--- a/manifest-chrome.partial.json
+++ b/manifest-chrome.partial.json
@@ -3,6 +3,7 @@
     "permissions": ["scripting", "webNavigation", "offscreen"],
     "host_permissions": [
         "http://localhost/*",
+        "https://cses.fi/*",
         "https://codeforces.com/*",
         "https://maang.in/*"
     ],
diff --git a/manifest-firefox.partial.json b/manifest-firefox.partial.json
index fd764b9..ca092cf 100644
--- a/manifest-firefox.partial.json
+++ b/manifest-firefox.partial.json
@@ -6,6 +6,7 @@
     "permissions": [
         "scripting",
         "*://localhost/*",
+        "https://cses.fi/*",
         "*://codeforces.com/*",
         "*://maang.in/*",
         "webNavigation"
diff --git a/readme.md b/readme.md
index 945889c..d38ce65 100644
--- a/readme.md
+++ b/readme.md
@@ -1,7 +1,7 @@
 # ![ICON](icon-48.png) cph-submit
 
-Browser add on that enables Codeforces submit with
-[Competitive Programming Helper](https://github.com/agrawal-d/cph)
+Browser add-on that enables direct submission on Codeforces,CSES and Maang.in
+with[Competitive Programming Helper](https://github.com/agrawal-d/cph).
 
 Available for Firefox and Google Chrome.
 
diff --git a/src/csesInjectedScript.ts b/src/csesInjectedScript.ts
new file mode 100644
index 0000000..626160d
--- /dev/null
+++ b/src/csesInjectedScript.ts
@@ -0,0 +1,102 @@
+import { ContentScriptData } from './types';
+import log from './log';
+
+declare const browser: any;
+if (typeof browser !== 'undefined') {
+    self.chrome = browser;
+}
+
+log('cph-submit cses script injected');
+
+const extMap: Record<string, string> = {
+    cpp: 'solution.cpp',
+    c: 'solution.c',
+    java: 'solution.java',
+    python: 'solution.py',
+    rust: 'solution.rs',
+    javascript: 'solution.js',
+    ruby: 'solution.rb',
+    haskell: 'solution.hs',
+    scala: 'solution.scala',
+    pascal: 'solution.pas',
+};
+
+const langMap: Record<string, string> = {
+    cpp: 'C++',
+    c: 'C',
+    java: 'Java',
+    python: 'Python3',
+    rust: 'Rust',
+    javascript: 'Node.js',
+    ruby: 'Ruby',
+    haskell: 'Haskell',
+    scala: 'Scala',
+    pascal: 'Pascal',
+};
+const idToKey: Record<number, string> = {
+    54: 'cpp',
+    50: 'cpp',
+    42: 'cpp',
+    61: 'cpp',
+    89: 'cpp',
+    91: 'cpp',
+    59: 'cpp',
+    2: 'cpp',
+    52: 'cpp',
+    43: 'c',
+    36: 'java',
+    60: 'java',
+    87: 'java',
+    7: 'python',
+    31: 'python',
+    40: 'python',
+    41: 'python',
+    70: 'python',
+    75: 'rust',
+    98: 'rust',
+    34: 'javascript',
+    55: 'javascript',
+    67: 'ruby',
+    12: 'haskell',
+    20: 'scala',
+    3: 'pascal',
+    4: 'pascal',
+    51: 'pascal',
+};
+
+chrome.runtime.onMessage.addListener((message) => {
+    if (message.type !== 'cph-submit-cses') return;
+
+    const { sourceCode, languageId } = message;
+
+    const form = document.querySelector('form');
+    if (!form) {
+        alert('CSES form not found');
+        log('CSES form not found');
+        return;
+    }
+
+    const fileInput = form.querySelector(
+        'input[type="file"]',
+    ) as HTMLInputElement;
+    if (fileInput) {
+        const langKey = idToKey[languageId] ?? 'cpp';
+
+        const fileName = extMap[langKey] ?? 'solution.cpp';
+        const file = new File([sourceCode], fileName, { type: 'text/plain' });
+        const dt = new DataTransfer();
+        dt.items.add(file);
+        fileInput.files = dt.files;
+    }
+
+    const langSelect = form.querySelector(
+        'select[name="lang"]',
+    ) as HTMLSelectElement;
+    if (langSelect) {
+        const langKey = idToKey[languageId] ?? 'cpp';
+        langSelect.value = langMap[langKey] ?? 'C++';
+    }
+
+    form.submit();
+    log('CSES form submitted');
+});
diff --git a/src/handleSubmit.ts b/src/handleSubmit.ts
index 8e2aaf4..81685a0 100644
--- a/src/handleSubmit.ts
+++ b/src/handleSubmit.ts
@@ -91,6 +91,15 @@ export const isAlgoZenithProblem = (problemUrl: string) => {
         return false;
     }
 };
+export const isCSESProblem = (problemUrl: string) => {
+    console.log(`problemURL-CSES ${problemUrl} `);
+    try {
+        const url = new URL(problemUrl);
+        return url.hostname === 'cses.fi' || url.hostname.endsWith('.cses.fi');
+    } catch {
+        return false;
+    }
+};
 
 export const handleAlgoZenithSubmit = async (
     problemName: string,
@@ -140,7 +149,59 @@ export const handleAlgoZenithSubmit = async (
         },
     );
 };
+export const handleCSESSubmit = async (
+    problemName: string,
+    languageId: number,
+    sourceCode: string,
+    problemUrl: string,
+) => {
+    log('Handling CSES submit for', problemUrl);
+    log('isCSES check:', isCSESProblem(problemUrl));
 
+    const submitUrl = problemUrl
+        .replace('/task/', '/submit/')
+        .replace(/\/?$/, '/');
+
+    const tab = await chrome.tabs.create({
+        active: true,
+        url: submitUrl,
+    });
+
+    const tabId = tab.id as number;
+    chrome.windows.update(tab.windowId, { focused: true });
+
+    chrome.tabs.onUpdated.addListener(
+        function listener(updatedTabId, changeInfo) {
+            if (updatedTabId === tabId && changeInfo.status === 'complete') {
+                chrome.tabs.onUpdated.removeListener(listener);
+
+                setTimeout(async () => {
+                    if (typeof chrome !== 'undefined' && chrome.scripting) {
+                        await chrome.scripting.executeScript({
+                            target: { tabId, allFrames: false },
+                            files: ['/dist/csesInjectedScript.js'],
+                        });
+                    } else if (typeof browser !== 'undefined') {
+                        await browser.tabs.executeScript(tabId, {
+                            file: '/dist/csesInjectedScript.js',
+                        });
+                    }
+                    setTimeout(() => {
+                        chrome.tabs.sendMessage(tabId, {
+                            type: 'cph-submit-cses',
+                            problemName,
+                            languageId,
+                            sourceCode,
+                            url: problemUrl,
+                        });
+
+                        log('Message sent to CSES tab');
+                    }, 500);
+                }, 1000);
+            }
+        },
+    );
+};
 export const handleSubmit = async (
     problemName: string,
     languageId: number,
@@ -160,6 +221,14 @@ export const handleSubmit = async (
             problemUrl,
         );
     }
+    if (isCSESProblem(problemUrl)) {
+        return handleCSESSubmit(
+            problemName,
+            languageId,
+            sourceCode,
+            problemUrl,
+        );
+    }
 
     const submitTarget = resolveSubmitTarget(problemUrl);
 
diff --git a/webpack.config.js b/webpack.config.js
index 92da5af..d53f0e1 100644
--- a/webpack.config.js
+++ b/webpack.config.js
@@ -6,6 +6,7 @@ module.exports = {
         backgroundScript: './src/backgroundScript.ts',
         injectedScript: './src/injectedScript.ts',
         algoZenithInjectedScript: './src/algoZenithInjectedScript.ts',
+        csesInjectedScript: './src/csesInjectedScript.ts',
         offscreen: './src/offscreen.ts',
     },
     output: {