versioned_docs/version-1.1.0/guide/javascript/configuration.md

---
title: Configuration
sidebar_position: 2
id: configuration
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  this work for additional information regarding copyright ownership.
  The ASF licenses this file to You under the Apache License, Version 2.0
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---

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

## Basic Configuration

```ts
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

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

const fory = new Fory({
  ref: true,
  compatible: true,
  maxDepth: 100,
  maxBinarySize: 64 * 1024 * 1024,
  maxCollectionSize: 1_000_000,
  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          |
| `maxBinarySize`            | 64 MiB      | Maximum bytes accepted for any single binary field                                    |
| `maxCollectionSize`        | `1_000_000` | Maximum elements accepted in any list, set, or map                                    |
| `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:

```ts
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](references.md) and
[Schema Metadata](schema-metadata.md).

## Compatible Schema Evolution

Compatible mode is the default:

```ts
const fory = new Fory();
```

Use this default for rolling upgrades, independently deployed services, and cross-language payloads.
You can opt out for one stable struct with `evolving: false`; see
[Schema Evolution](schema-evolution.md).

## Optional HPS String Path

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

```ts
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`, `maxBinarySize`, and `maxCollectionSize` for the maximum payload shape your
  service accepts.
- Prefer explicit `Type.struct(...)` schemas over `Type.any()` for untrusted input.
- Pass `hps` only from the official package version you deploy with the runtime.

## Related Topics

- [Basic Serialization](basic-serialization.md)
- [Schema Metadata](schema-metadata.md)
- [Schema Evolution](schema-evolution.md)
- [References](references.md)