diff --git a/src/vm_builtins.c b/src/vm_builtins.c
index d61d9e3c..b25b0937 100644
--- a/src/vm_builtins.c
+++ b/src/vm_builtins.c
@@ -6385,7 +6385,49 @@ static RValue builtin_buffer_save(MAYBE_UNUSED VMContext* ctx, RValue* args, MAY
     return RValue_makeUndefined();
 }
 
-STUB_RETURN_ZERO(buffer_base64_encode)
+static RValue builtin_buffer_base64_encode(MAYBE_UNUSED VMContext* ctx, RValue* args, MAYBE_UNUSED int32_t argCount) {
+    Runner* runner = ctx->runner;
+    if (3 > argCount) return RValue_makeOwnedString(safeStrdup(""));
+
+    int32_t id = RValue_toInt32(args[0]);
+    GmlBuffer* buf = gmlBufferGet(runner, id);
+    if (buf == nullptr) return RValue_makeOwnedString(safeStrdup(""));
+
+    int32_t offset = RValue_toInt32(args[1]);
+    size_t size = RValue_toInt32(args[2]);
+
+    int32_t maxBoundary = (buf->type == GML_BUFFER_GROW) ? buf->usedSize : buf->size;
+
+    if (offset < 0 || offset >= maxBoundary || size <= 0) {
+        return RValue_makeOwnedString(safeStrdup(""));
+    }
+
+    if (offset + size > (size_t)maxBoundary) {
+        size = (size_t)(maxBoundary - offset);
+    }
+
+    char* out = safeMalloc(BASE64_ENCODE_OUT_SIZE(size));
+    base64_encode((const unsigned char*) buf->data + offset, size, out);
+    return RValue_makeOwnedString(out);
+}
+
+static RValue builtin_buffer_base64_decode(MAYBE_UNUSED VMContext* ctx, RValue* args, MAYBE_UNUSED int32_t argCount) {
+    Runner* runner = ctx->runner;
+    if (2 > argCount) return RValue_makeOwnedString(safeStrdup(""));
+    char* input = RValue_toString(args[1]);
+    unsigned int inLen = (unsigned int) strlen(input);
+    size_t outLen = BASE64_DECODE_OUT_SIZE(inLen);
+    char* out = safeMalloc(outLen);
+    base64_decode((const unsigned char*) input, inLen, out);
+    free(input);
+    int32_t id = gmlBufferCreate(runner, outLen, GML_BUFFER_GROW, 1);
+    GmlBuffer* buf = gmlBufferGet(runner, id);
+    free(buf->data);
+    buf->data = out;
+    buf->size = outLen;
+    buf->usedSize = outLen;
+    return RValue_makeReal((GMLReal) id);
+}
 
 static RValue builtin_base64_encode(MAYBE_UNUSED VMContext* ctx, RValue* args, MAYBE_UNUSED int32_t argCount) {
     if (1 > argCount) return RValue_makeOwnedString(safeStrdup(""));
@@ -11292,6 +11334,7 @@ void VMBuiltins_registerAll(VMContext* ctx) {
     VM_registerBuiltin(ctx, "buffer_load", builtin_buffer_load);
     VM_registerBuiltin(ctx, "buffer_save", builtin_buffer_save);
     VM_registerBuiltin(ctx, "buffer_base64_encode", builtin_buffer_base64_encode);
+    VM_registerBuiltin(ctx, "buffer_base64_decode", builtin_buffer_base64_decode);
     VM_registerBuiltin(ctx, "base64_encode", builtin_base64_encode);
     VM_registerBuiltin(ctx, "base64_decode", builtin_base64_decode);
     VM_registerBuiltin(ctx, "buffer_md5", builtin_buffer_md5);