diff --git a/package.json b/package.json
index 09d1fd5..4cc9d1a 100644
--- a/package.json
+++ b/package.json
@@ -50,6 +50,7 @@
   "scripts": {
     "test:integration": "mocha --exit",
     "test:package": "mocha test/testPackageFiles.js --exit",
+    "test:unit": "mocha test/testEntityFilter.js --exit",
     "test": "npm run test:integration",
     "build:tsc": "tsc -p tsconfig.build.json",
     "build": "npm run build:tsc",
diff --git a/src/lib/entityFilter.ts b/src/lib/entityFilter.ts
new file mode 100644
index 0000000..1f73d15
--- /dev/null
+++ b/src/lib/entityFilter.ts
@@ -0,0 +1,25 @@
+/**
+ * Returns true if entityId matches any of the supplied glob patterns.
+ * Glob syntax: `*` is the only wildcard and matches any sequence of characters
+ * (including dots). All other characters are matched literally (regex
+ * metacharacters are escaped). Matching is case-sensitive and anchored to
+ * the full entity_id.
+ *
+ * An empty patterns array always returns false.
+ */
+export function isExcluded(entityId: string, patterns: string[]): boolean {
+    if (!patterns || patterns.length === 0) {
+        return false;
+    }
+    for (const pattern of patterns) {
+        if (globToRegex(pattern).test(entityId)) {
+            return true;
+        }
+    }
+    return false;
+}
+
+function globToRegex(pattern: string): RegExp {
+    const escaped = pattern.replace(/[.+?^${}()|[\]\\]/g, '\\$&').replace(/\*/g, '.*');
+    return new RegExp(`^${escaped}$`);
+}
diff --git a/test/testEntityFilter.js b/test/testEntityFilter.js
new file mode 100644
index 0000000..5dc12a4
--- /dev/null
+++ b/test/testEntityFilter.js
@@ -0,0 +1,47 @@
+const { expect } = require('chai');
+const { isExcluded } = require('../build/lib/entityFilter');
+
+describe('entityFilter.isExcluded', () => {
+    it('returns false for an empty pattern list', () => {
+        expect(isExcluded('switch.iob_anything', [])).to.equal(false);
+    });
+
+    it('matches a simple glob with leading wildcard', () => {
+        expect(isExcluded('switch.iob_shelly_xyz', ['*.iob_*'])).to.equal(true);
+    });
+
+    it('matches the bridge mirror naming pattern', () => {
+        expect(isExcluded('light.iob_ha_eg_wz1__e_licht_decke', ['*.iob_*__*'])).to.equal(true);
+    });
+
+    it('handles entities that miss a required literal segment', () => {
+        // *.iob_*__* requires the literal `__` segment — entities without it do not match
+        expect(isExcluded('switch.iob_', ['*.iob_*__*'])).to.equal(false);
+        expect(isExcluded('switch.iob_foo', ['*.iob_*__*'])).to.equal(false);
+        // Naming-Convention safety: similarly named entities without `__` are safe
+        expect(isExcluded('sensor.scheune_temperatur', ['*.sc_*__*'])).to.equal(false);
+    });
+
+    it('matches multiple patterns (OR semantic)', () => {
+        const patterns = ['*.iob_*__*', '*.knx_*', '*.ha_*__*'];
+        expect(isExcluded('switch.knx_foo', patterns)).to.equal(true);
+        expect(isExcluded('switch.ha_eg_wz1__e_licht_decke', patterns)).to.equal(true);
+        expect(isExcluded('switch.something_else', patterns)).to.equal(false);
+    });
+
+    it('is case sensitive', () => {
+        expect(isExcluded('switch.IOB_foo', ['*.iob_*'])).to.equal(false);
+        expect(isExcluded('switch.iob_foo', ['*.IOB_*'])).to.equal(false);
+    });
+
+    it('treats * as matching any characters including dots', () => {
+        // We use full entity_id including the leading domain, so this is fine.
+        expect(isExcluded('switch.iob_foo', ['*foo*'])).to.equal(true);
+    });
+
+    it('escapes regex metacharacters in patterns', () => {
+        // `.` in pattern matches literal `.`, not "any char"
+        expect(isExcluded('switch.iob_foo', ['switch.iob_foo'])).to.equal(true);
+        expect(isExcluded('switchXiob_foo', ['switch.iob_foo'])).to.equal(false);
+    });
+});