docs/object-serialization/javascript/security.md

---
title: Security
sidebar_position: 99
id: security
license: |
  Licensed to the Apache Software Foundation (ASF) under one or more
  contributor license agreements.  See the NOTICE file distributed with
  this work for additional information regarding copyright ownership.
  The ASF licenses this file to You under the Apache License, Version 2.0
  (the "License"); you may not use this file except in compliance with
  the License.  You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

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---

Use this page when a JavaScript/TypeScript reader accepts bytes from outside the application's trust boundary.
Fory reconstructs application values; it does not authenticate the sender, protect transport
integrity, or decide whether a valid value is authorized for a business operation.

## Application boundary

Before deserialization:

- Authenticate the sender and protect message integrity at the transport or storage layer.
- Enforce request or file size, timeout, and concurrency limits outside Fory.
- Register only the application types the endpoint accepts and configure the reader before its
  first root operation.
- Validate the deserialized value against application authorization and domain rules before use.

## Runtime safeguards

Security-related configuration:

- Register only the expected schemas before deserializing untrusted payloads.
- Set `maxDepth` for the maximum nesting depth your service accepts.
- Set `maxGraphMemoryBytes` as an approximate gate for collection, map, array, struct, and
  object-heavy payloads. It is not an exact heap cap; leaf values are gated by remaining input
  bytes.
- Keep `maxTypeFields` and `maxTypeMetaBytes` at their defaults unless the data
  is not malicious and a trusted peer sends larger remote metadata.
- Keep `maxSchemaVersionsPerType` and
  `maxAverageSchemaVersionsPerType` at their defaults unless the data is not
  malicious and a trusted peer sends many remote schema versions.
- Prefer explicit `Type.struct(...)` schemas over `Type.any()` for untrusted input.
- Pass `hps` only from the official package version you deploy with Fory.

## Verification

Add negative tests for the boundary as well as normal round trips. Verify that the configured reader
rejects unexpected application types, excessive nesting, resource-limit violations, and malformed
input. After a failed read, verify that a valid root can still be read with the reusable runtime.

See [Configuration](configuration.md) for the complete option reference and
[Type Registration](type-registration.md) for the runtime's registration API.