docs/guide/javascript/configuration.md

title: Configuration sidebar_position: 2 id: configuration 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

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Fory JavaScript is an xlang-only implementation. new Fory() writes xlang payloads and uses compatible schema evolution by default. There is no native-mode switch in the JavaScript API.

Basic Configuration

import Fory from "@apache-fory/core";

const fory = new Fory();

Create one Fory instance per application area and reuse it. Registration generates and caches serializer code for each schema.

Constructor Options

import Fory from "@apache-fory/core";
import hps from "@apache-fory/hps";

const fory = new Fory({
  ref: true,
  compatible: true,
  maxDepth: 100,
  maxGraphMemoryBytes: 128 * 1024 * 1024,
  maxTypeFields: 512,
  maxTypeMetaBytes: 4096,
  maxSchemaVersionsPerType: 10,
  maxAverageSchemaVersionsPerType: 3,
  hps,
});

Option	Default	Description
`ref`	`false`	Enable reference tracking for shared or circular object graphs
`compatible`	`true`	Allow field additions/removals without breaking existing messages
`maxDepth`	`50`	Maximum nesting depth. Must be `>= 2`. Increase for deeply nested structures
`maxGraphMemoryBytes`	`128 MiB`	Approximate graph-memory gate accepted during one root deserialization
`maxTypeFields`	`512`	Maximum fields accepted in one received remote struct metadata body
`maxTypeMetaBytes`	`4096`	Maximum encoded body bytes accepted for one received TypeMeta body
`maxSchemaVersionsPerType`	`10`	Maximum accepted remote metadata versions for one logical type
`maxAverageSchemaVersionsPerType`	`3`	Average accepted remote metadata versions across accepted remote types
`useSliceString`	`false`	Optional string-reading optimization for Node.js. Leave at default unless benchmarked
`hps`	unset	Optional fast string helper from `@apache-fory/hps` (Node.js 20+)
`hooks.afterCodeGenerated`	unset	Callback to inspect the generated serializer code, useful for debugging

Reference Tracking

Global reference tracking must be enabled before field-level reference metadata can take effect:

const fory = new Fory({ ref: true });

Then mark reference-tracked fields in the schema, for example with Type.struct("example.node").setTrackingRef(true). See References and Schema Metadata.

Compatible Schema Evolution

Compatible mode is the default. To use faster serialization and smaller size:

const fory = new Fory({ compatible: false });

Use compatible mode for rolling upgrades, independently deployed services, and cross-language payloads. Use compatible: false only when every reader and writer always uses the same struct schema and you want faster serialization and smaller size. For individual structs, evolving: false applies the same opt-out to that struct. For cross-language payloads, set compatible: false only after verifying that every language uses the same schema, or when native types are generated from Fory schema IDL. See Schema Evolution.

Graph Memory Budget

maxGraphMemoryBytes sets an approximate graph-memory gate for one root deserialization. The estimate mainly covers materialized arrays, sets, maps, structs, and objects. It skips leaf values such as strings, binary data, primitive scalars, and dense primitive arrays, so actual JavaScript heap use can be higher than this value. Leaf values remain protected by byte-availability checks: if the unread input does not contain enough bytes, Fory will not read or create that leaf value. The default is a fixed 128 MiB and is not derived from input size.

Use a positive byte value to set an explicit lower or higher limit:

const fory = new Fory({
  maxGraphMemoryBytes: 32 * 1024 * 1024,
});

Explicit non-positive values are rejected when the runtime is created.

String, binary, and dedicated dense primitive array payloads keep their normal byte-size checks and do not consume this graph budget. Raise the limit only for trusted workloads that legitimately contain very compact object graphs.

Optional HPS String Path

@apache-fory/hps provides an optional Node.js string fast path:

import hps from "@apache-fory/hps";

const fory = new Fory({ hps });

Leave this unset unless you run on Node.js 20+ and have benchmarked your workload.

Security

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.