diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
new file mode 100644
index 0000000..7677470
--- /dev/null
+++ b/.github/workflows/test.yml
@@ -0,0 +1,28 @@
+name: Node.js CI
+
+on:
+  push:
+    branches: [ main, dev ]
+  pull_request:
+    branches: [ main ]
+
+env:
+  FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: true
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v6
+        with:
+          node-version: '24'
+          cache: 'npm'
+
+      - name: Install dependencies
+        run: npm install
+
+      - name: Run tests
+        run: npm test
\ No newline at end of file
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..b729dcb
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,31 @@
+# Logs
+logs
+*.log
+npm-debug.log*
+
+# Editors
+.vscode/
+
+# Dependency directories
+node_modules/
+
+# Optional test coverage reports
+coverage/
+
+# Optional npm cache directory
+.npm
+
+# Output of 'npm pack'
+*.tgz
+
+# OS files
+Thumbs.db
+Thumbs.db:encryptable
+ehthumbs.db
+[Dd]esktop.ini
+.DS_Store
+.localized
+__MACOSX/
+.AppleDouble
+.LSOverride
+Icon[]
diff --git a/README.md b/README.md
index f7e30c9..1317c31 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,46 @@
 # jsonkdiff
-Compare multiple JSON files and find non-common keys. Generates a per-file report of unique keys to help identify schema drift.
+
+![Build status](https://github.com/grrtbrtr/jsonkdiff/actions/workflows/test.yml/badge.svg)
+![NPM version](https://img.shields.io/npm/v/jsonkdiff)
+
+A lightweight, zero-dependency CLI tool to compare multiple JSON files and identify missing (non-common) keys.
+It generates a per-file report of unique keys to help identify schema drift.
+
+Perfect for auditing translation files, config sets, or API mocks.
+
+## Features
+
+- **Deep comparison**: Recursively traverses objects to find missing keys at any nesting level.
+- **Compare many files**: Compares 2 or more files, using the union of all keys as the "master" schema.
+- **Per-file reports**: Aggregates all unique keys and tells you exactly what is missing from each file.
+- **Zero dependencies**: Built with pure Node.js.
+
+## Installation & usage
+
+### Run without installing
+
+```bash
+npx jsonkdiff file1.json file2.json file3.json
+```
+
+### Global installation
+
+```bash
+npm install -g jsonkdiff
+jsonkdiff file1.json file2.json file3.json
+```
+
+## Example output
+
+If `en.json` has `{"auth": {"login": "Log In"}}` and `es.json` is empty, `jsonkdiff` will report:
+```JSON
+{
+  "es.json": [
+    "auth",
+    "auth.login"
+  ]
+}
+```
+
+## License
+[GPL-3.0-only](./LICENSE)
\ No newline at end of file
diff --git a/bin/cli.js b/bin/cli.js
new file mode 100644
index 0000000..76164d0
--- /dev/null
+++ b/bin/cli.js
@@ -0,0 +1,58 @@
+#!/usr/bin/env node
+import { compareKeys } from './../src/index.js';
+
+const STYLES = Object.freeze({
+  reset: '\x1b[0m',
+  bold: '\x1b[1m',
+  red: '\x1b[31m',
+  green: '\x1b[32m',
+  yellow: '\x1b[33m',
+  blue: '\x1b[34m'
+});
+
+const files = process.argv.slice(2);
+
+if (files.length < 2) {
+  console.log(`\n${STYLES.bold}Usage:${STYLES.reset} jsonkdiff <file1.json> <file2.json> ...`);
+  process.exit(0);
+}
+
+async function main() {
+  try {
+    const report = await compareKeys(files);
+    
+    console.log(`\n${STYLES.blue}${STYLES.bold}--- JSON Key Diff Report ---${STYLES.reset}\n`);
+
+    let hasIssues = false;
+    for (const [fileName, missing] of Object.entries(report)) {
+      if (missing.length > 0) {
+        hasIssues = true;
+        console.log(`${STYLES.yellow}File: ${fileName}${STYLES.reset}`);
+        missing.forEach(key => {
+          console.log(`  ${STYLES.red}× Missing key:${STYLES.reset} ${key}`);
+        });
+        console.log(''); 
+      }
+    }
+
+    if (!hasIssues) {
+      console.log(`${STYLES.green}✔ All files share the exact same keys!${STYLES.reset}\n`);
+      process.exit(0);
+    } else {
+      process.exit(1);
+    }
+  } catch (err) {
+    if (err.code === 'ENOENT') {
+      console.error(`${STYLES.red}${STYLES.bold}Error:${STYLES.reset} Could not find file "${err.path}"`);
+    } else if (err instanceof SyntaxError) {
+      console.error(`${STYLES.red}${STYLES.bold}Error:${STYLES.reset} Invalid JSON in one of the files.`);
+    } else if (err.code === 'EISDIR') {
+      console.error(`${STYLES.red}${STYLES.bold}Error:${STYLES.reset} One of the given paths is a directory, not a file.`);
+    } else {
+      console.error(`${STYLES.red}${STYLES.bold}Error:${STYLES.reset} ${err.message}`);
+    }
+    process.exit(1);
+  }
+}
+
+main();
\ No newline at end of file
diff --git a/package-lock.json b/package-lock.json
new file mode 100644
index 0000000..54202d8
--- /dev/null
+++ b/package-lock.json
@@ -0,0 +1,19 @@
+{
+  "name": "jsonkdiff",
+  "version": "1.0.0",
+  "lockfileVersion": 3,
+  "requires": true,
+  "packages": {
+    "": {
+      "name": "jsonkdiff",
+      "version": "1.0.0",
+      "license": "GPL-3.0-only",
+      "bin": {
+        "jsonkdiff": "bin/cli.js"
+      },
+      "engines": {
+        "node": ">=20.0.0"
+      }
+    }
+  }
+}
diff --git a/package.json b/package.json
new file mode 100644
index 0000000..afc1deb
--- /dev/null
+++ b/package.json
@@ -0,0 +1,45 @@
+{
+  "name": "jsonkdiff",
+  "version": "1.0.0",
+  "description": "Compare multiple JSON files and find non-common keys. Generates a per-file report of unique keys to help identify schema drift.",
+  "keywords": [
+    "json",
+    "json-keys",
+    "json-comparison",
+    "diff",
+    "schema",
+    "schema-drift",
+    "comparison",
+    "cli",
+    "devtools"
+  ],
+  "homepage": "https://github.com/grrtbrtr/jsonkdiff#readme",
+  "bugs": {
+    "url": "https://github.com/grrtbrtr/jsonkdiff/issues"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/grrtbrtr/jsonkdiff.git"
+  },
+  "license": "GPL-3.0-only",
+  "author": "Gerrit Bertier <gerrit.bertier@gmail.com>",
+  "type": "module",
+  "main": "src/index.js",
+  "bin": {
+    "jsonkdiff": "bin/cli.js"
+  },
+  "files": [
+    "src/",
+    "bin/",
+    "README.md",
+    "LICENSE"
+  ],
+  "engines": {
+    "node": ">=20.0.0"
+  },
+  "scripts": {
+    "test": "node --test \"test/**/*.test.js\"",
+    "start": "node ./bin/cli.js",
+    "prepublishOnly": "npm test"
+  }
+}
diff --git a/src/index.js b/src/index.js
new file mode 100644
index 0000000..80ca10b
--- /dev/null
+++ b/src/index.js
@@ -0,0 +1,48 @@
+import fs from 'node:fs/promises';
+import path from 'node:path';
+
+import { getDeepKeys } from './utils/object-utils.js';
+
+/**
+ * Identify missing keys across multiple datasets.
+ * It aggregates all unique keys found across all objects and identifies
+ * which specific keys are absent from each individual object.
+ * 
+ * @param {Array.<{name: string, object: object}>} datasets - An array of objects containing a name and the actual object.
+ * @returns {Object.<string, string[]>} A report where keys are the object names and values are arrays of missing key paths.
+ */
+export function computeKeyDiff(datasets) {
+  const allKeys = new Set();
+  const processedData = datasets.map(ds => {
+    const keys = getDeepKeys(ds.object);
+    keys.forEach(k => allKeys.add(k));
+    return { name: ds.name, keys };
+  });
+
+  const report = {};
+  for (const item of processedData) {
+    report[item.name] = [...allKeys].filter(k => !item.keys.includes(k));
+  }
+  return report;
+}
+
+/**
+ * Reads multiple JSON files and performs a key-level diff.
+ * @async
+ * 
+ * @param {string[]} filePaths - An array of relative or absolute paths to JSON files.
+ * @returns {Promise<Object.<string, string[]>>} A promise that resolves to the diff report.
+ * @throws {Error} Throws an error if any file cannot be read or parsed as valid JSON.
+ */
+export async function compareKeys(filePaths) {
+  const datasets = await Promise.all(filePaths.map(async (filePath) => {
+    const absPath = path.resolve(filePath);
+    const file = await fs.readFile(absPath, 'utf-8');
+    return {
+      name: filePath,
+      object: JSON.parse(file)
+    };
+  }));
+
+  return computeKeyDiff(datasets);
+}
\ No newline at end of file
diff --git a/src/utils/object-utils.js b/src/utils/object-utils.js
new file mode 100644
index 0000000..180dc3e
--- /dev/null
+++ b/src/utils/object-utils.js
@@ -0,0 +1,20 @@
+/**
+ * Recursively flattens an object into a list of key paths.
+ * Example: { a: { b: 1 } } -> ["a", "a.b"]
+ * @param {object} obj - The object to traverse and flatten.
+ * @param {string} [prefix] - The prefix to append to the key (used for nesting).
+ * 
+ * @returns {Array.<string>} An array of keys.
+ */
+export function getDeepKeys(obj, prefix = '') {
+  let keys = [];
+  for (const key in obj) {
+    const fullPath = prefix ? `${prefix}.${key}` : key;
+    keys.push(fullPath);
+    
+    if (typeof obj[key] === 'object' && obj[key] !== null && !Array.isArray(obj[key])) {
+      keys = keys.concat(getDeepKeys(obj[key], fullPath));
+    }
+  }
+  return keys;
+}
\ No newline at end of file
diff --git a/test/index.test.js b/test/index.test.js
new file mode 100644
index 0000000..4fc267a
--- /dev/null
+++ b/test/index.test.js
@@ -0,0 +1,68 @@
+import assert from 'node:assert';
+import test from 'node:test';
+import fs from 'node:fs/promises';
+import os from 'node:os';
+import path from 'node:path';
+
+import { compareKeys, computeKeyDiff } from './../src/index.js';
+
+test('Unit: computeKeyDiff', async (t) => {
+  await t.test('identifies missing keys between two files', () => {
+    const datasets = [
+      { name: 'A.json', object: { id: 1, name: 'test' } },
+      { name: 'B.json', object: { id: 2 } }
+    ];
+    const result = computeKeyDiff(datasets);
+
+    assert.deepStrictEqual(result['A.json'], []);
+    assert.deepStrictEqual(result['B.json'], ['name']);
+  });
+
+  await t.test('identifies keys missing from both sides simultaneously', () => {
+    const datasets = [
+      { name: 'A.json', object: { onlyA: 1 } },
+      { name: 'B.json', object: { onlyB: 1 } }
+    ];
+    const result = computeKeyDiff(datasets);
+
+    assert.deepStrictEqual(result['A.json'], ['onlyB']);
+    assert.deepStrictEqual(result['B.json'], ['onlyA']);
+  });
+});
+
+test('Integration: compareKeys', async (t) => {
+  const file1 = path.join(os.tmpdir(), `jsonkdiff_1_${Date.now()}.json`);
+  const file2 = path.join(os.tmpdir(), `jsonkdiff_2_${Date.now()}.json`);
+
+  try {
+    await fs.writeFile(file1, JSON.stringify({ active: true, meta: { id: 1 } }));
+    await fs.writeFile(file2, JSON.stringify({ active: true }));
+
+    await t.test('reads files and returns correct diff', async () => {
+      const report = await compareKeys([file1, file2]);
+      assert.ok(report[file2].includes('meta'));
+      assert.ok(report[file2].includes('meta.id'));
+    });
+
+    await t.test('throws error on invalid JSON', async () => {
+      const brokenFile = path.join(os.tmpdir(), `jsonkdiff_broken_${Date.now()}.json`);
+      await fs.writeFile(brokenFile, '{ invalid json }');
+      
+      await assert.rejects(
+        async () => {
+          await compareKeys([brokenFile]);
+        },
+        {
+          name: 'SyntaxError'
+        }
+      );
+
+      await fs.unlink(brokenFile);
+    });
+  } finally {
+    await Promise.all([
+      fs.unlink(file1).catch(() => {}),
+      fs.unlink(file2).catch(() => {}),
+    ]);
+  }
+});
\ No newline at end of file
diff --git a/test/utils/object-utils.test.js b/test/utils/object-utils.test.js
new file mode 100644
index 0000000..a877069
--- /dev/null
+++ b/test/utils/object-utils.test.js
@@ -0,0 +1,28 @@
+import test from 'node:test';
+import assert from 'node:assert';
+
+import { getDeepKeys } from './../../src/utils/object-utils.js';
+
+test('Unit: getDeepKeys', async (t) => {
+  await t.test('flattens nested objects', () => {
+    const input = { a: { b: { c: 1 } } };
+    const expected = ['a', 'a.b', 'a.b.c'];
+    assert.deepStrictEqual(getDeepKeys(input), expected);
+  });
+
+  await t.test('handles empty objects', () => {
+    assert.deepStrictEqual(getDeepKeys({}), []);
+  });
+
+  await t.test('handles null values without crashing', () => {
+    const input = { a: null, b: { c: null } };
+    const expected = ['a', 'b', 'b.c']; 
+    assert.deepStrictEqual(getDeepKeys(input), expected);
+  });
+
+  await t.test('treats arrays as leaf nodes (values)', () => {
+    const input = { list: [1, 2, 3] };
+    const expected = ['list'];
+    assert.deepStrictEqual(getDeepKeys(input), expected);
+  });
+});
\ No newline at end of file