diff --git a/.eslintrc.yml b/.eslintrc.yml
deleted file mode 100644
index bc57d11..0000000
--- a/.eslintrc.yml
+++ /dev/null
@@ -1 +0,0 @@
-extends: cheminfo-typescript
diff --git a/eslint.config.mjs b/eslint.config.mjs
new file mode 100644
index 0000000..9ced323
--- /dev/null
+++ b/eslint.config.mjs
@@ -0,0 +1,9 @@
+import cheminfo from 'eslint-config-cheminfo-typescript';
+
+export default [
+  ...cheminfo,
+  {
+    languageOptions: {},
+    rules: {},
+  },
+];
diff --git a/package.json b/package.json
index 4b97233..395c0b1 100644
--- a/package.json
+++ b/package.json
@@ -23,7 +23,7 @@
     "prettier-write": "prettier --write src",
     "test": "npm run test-coverage && npm run eslint && npm run prettier && npm run check-types",
     "test-coverage": "npm run test-only -- --coverage",
-    "test-only": "jest",
+    "test-only": "vitest run",
     "tsc": "npm run clean && npm run tsc-cjs && npm run tsc-esm",
     "tsc-cjs": "tsc --project tsconfig.cjs.json",
     "tsc-esm": "tsc --project tsconfig.esm.json"
@@ -36,22 +36,16 @@
     "url": "https://github.com/cheminfo/uint8-base64/issues"
   },
   "homepage": "https://github.com/cheminfo/uint8-base64#readme",
-  "jest": {
-    "preset": "ts-jest",
-    "testEnvironment": "node",
-    "testPathIgnorePatterns": [
-      "node_modules",
-      "data.ts"
-    ]
-  },
   "devDependencies": {
-    "@types/jest": "^27.0.1",
-    "eslint": "^7.32.0",
-    "eslint-config-cheminfo-typescript": "^8.0.9",
-    "jest": "^27.1.0",
-    "prettier": "^2.3.2",
-    "rimraf": "^3.0.2",
-    "ts-jest": "^27.0.5",
-    "typescript": "^4.4.2"
+    "@types/jest": "^29.5.14",
+    "@vitest/coverage-v8": "2.1.8",
+    "eslint": "^9.17.0",
+    "eslint-config-cheminfo-typescript": "^17.0.0",
+    "jest": "^29.7.0",
+    "prettier": "^3.4.2",
+    "rimraf": "^6.0.1",
+    "ts-jest": "^29.2.5",
+    "typescript": "^5.7.2",
+    "vitest": "^2.1.8"
   }
 }
diff --git a/src/__tests__/decode.test.ts b/src/__tests__/decode.test.ts
index 0f1b098..75cdefb 100644
--- a/src/__tests__/decode.test.ts
+++ b/src/__tests__/decode.test.ts
@@ -1,3 +1,5 @@
+import { describe, expect, it } from 'vitest';
+
 import { decode } from '..';
 
 import { tests, allBytes, base64AllBytes } from './data';
diff --git a/src/__tests__/encode.test.ts b/src/__tests__/encode.test.ts
index 1c83b37..a030a7d 100644
--- a/src/__tests__/encode.test.ts
+++ b/src/__tests__/encode.test.ts
@@ -1,3 +1,5 @@
+import { describe, expect, it } from 'vitest';
+
 import { encode } from '..';
 
 import { tests, allBytes, base64AllBytes } from './data';
diff --git a/src/decode.ts b/src/decode.ts
index eeac136..5d8be2d 100644
--- a/src/decode.ts
+++ b/src/decode.ts
@@ -10,6 +10,7 @@ const base64codes = Uint8Array.from([
 
 /**
  * Convert a Uint8Array containing a base64 encoded bytes to a Uint8Array containing decoded values
+ * @param input
  * @returns a Uint8Array containing the decoded bytes
  */
 
@@ -24,11 +25,10 @@ export function decode(
     throw new Error('Unable to parse base64 string.');
   }
 
-  let output = new Uint8Array(3 * (input.length / 4));
+  const output = new Uint8Array(3 * (input.length / 4));
   if (input.length === 0) return output;
 
-  const missingOctets =
-    input[input.length - 2] === 61 ? 2 : input[input.length - 1] === 61 ? 1 : 0;
+  const missingOctets = input.at(-2) === 61 ? 2 : input.at(-1) === 61 ? 1 : 0;
 
   for (let i = 0, j = 0; i < input.length; i += 4, j += 3) {
     const buffer =
diff --git a/src/encode.ts b/src/encode.ts
index 73a584c..0a1b30f 100644
--- a/src/encode.ts
+++ b/src/encode.ts
@@ -7,6 +7,7 @@ const base64codes = Uint8Array.from([
 
 /**
  * Convert a Uint8Array containing bytes to a Uint8Array containing the base64 encoded values
+ * @param input
  * @returns a Uint8Array containing the encoded bytes
  */
 
diff --git a/tsconfig.json b/tsconfig.json
index 4c83c06..950dc30 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -1,6 +1,7 @@
 {
   "compilerOptions": {
     "esModuleInterop": true,
+    "skipLibCheck": true,
     "moduleResolution": "node",
     "sourceMap": true,
     "strict": true,