diff --git a/src/formats/base64.ts b/src/formats/base64.ts
new file mode 100644
index 0000000..b1a84f7
--- /dev/null
+++ b/src/formats/base64.ts
@@ -0,0 +1,13 @@
+export type JSONBase64Format = {
+  name: "base64";
+};
+
+const base64Regex = /^(?:[A-Za-z\d+/]{4})*(?:[A-Za-z\d+/]{3}=|[A-Za-z\d+/]{2}==)?$/;
+
+export function inferBase64(value: string): JSONBase64Format | undefined {
+  if (base64Regex.exec(value)) {
+    return { name: "base64" };
+  }
+
+  return undefined;
+}
diff --git a/src/formats/index.ts b/src/formats/index.ts
index bc14475..652d40a 100644
--- a/src/formats/index.ts
+++ b/src/formats/index.ts
@@ -20,6 +20,7 @@ import { inferFirestoreTimestamp, JSONFirestoreTimestampFormat } from "./firesto
 import { inferJWT, JSONJWTStringFormat } from "./jwt";
 import { inferColor, JSONColorFormat } from "./color";
 import { inferCreditCard, JSONCreditCardFormat } from "./creditCard";
+import { inferBase64, JSONBase64Format } from "./base64";
 
 export {
   JSONHostnameFormat,
@@ -63,7 +64,8 @@ export type JSONStringFormat =
   | JSONSemverFormat
   | JSONJWTStringFormat
   | JSONColorFormat
-  | JSONCreditCardFormat;
+  | JSONCreditCardFormat
+  | JSONBase64Format;
 
 const formats = [
   inferUri,
@@ -86,6 +88,7 @@ const formats = [
   inferJWT,
   inferColor,
   inferCreditCard,
+  inferBase64,
 ];
 
 export function inferFormat(value: string): JSONStringFormat | undefined {
diff --git a/tests/stringFormats.test.ts b/tests/stringFormats.test.ts
index cf339ae..8d2d2f7 100644
--- a/tests/stringFormats.test.ts
+++ b/tests/stringFormats.test.ts
@@ -824,6 +824,30 @@ describe("credit cards", () => {
   );
 });
 
+describe("base64", () => {
+  test.each([
+    "Pmo9fEtDfWt7T11T",
+    "TG1BdGV8cU9BdHdkK3t6Y35WYmVxMiNiQH40Tw==",
+    "WzBjLiI7VnB2QlRib21denVIbiRj",
+    "VzFiIXhsOj5bIiU5PWhcSXdBdVslIms=",
+    "WzBFRFFOSSxjeFt7aiwo",
+    "fGZydkoqfENQPXt8bDR1Tlx1Kkk6aA==",
+    "LVwkb29bSiojT21HJU1B",
+    "cldpOnRUKy85",
+    "MnhuaVpjU0Zwdz1gZT5iY3ZaUQ==",
+    "amE3Rmg5OTVTbUAwI1J3NTZwK2lMXHxWR1tkJg==",
+  ])("%p should be infered as being a base64 string", (value) => {
+    expect(inferType(value)).toEqual({
+      name: "string",
+      value,
+      format: {
+        name: "base64",
+      },
+    });
+  });
+});
+
+
 describe("without format", () => {
   test.each(["46", "2244994945", "1212092628029698048"])(
     "%p should be inferred as having no format",