Configuration

Backend options

Pass a backend option to render to control which WASM module is used:

import { render } from "docxio";

// Use the minimal 441 KB WASM (browser-optimized)
const bytes = await render(doc, { backend: "minimal" });

// Use the full 920 KB WASM (includes template engine, validator)
const bytes = await render(doc, { backend: "full" });

// Auto-detect (default) -- tries minimal, falls back to full
const bytes = await render(doc);

The "minimal" backend generates XML parts inside WASM and assembles the ZIP archive in JavaScript via @docxio/zip. The "full" backend does everything in Rust, including ZIP packaging, template patching, and validation.

Pre-initializing WASM

By default, the WASM module is initialized lazily on the first render call. To avoid the cold-start delay, call initWasm() early:

import { initWasm } from "docxio";

// Call once at app startup
await initWasm();

This is useful in server environments where you want the first request to be fast.

Document metadata

Set metadata on the <document> root element:

<document
  creator="Jane Doe"
  title="Q4 Report"
  description="Quarterly financial report"
  keywords="finance, report, Q4"
>
  ...
</document>

These values are written to the docProps/core.xml part of the .docx file.

Default styles

By default, docxio includes a base set of Word styles (Normal, Heading1-6, etc.). To disable them:

<document useDefaultStyles={false}>
  ...
</document>

You can also provide custom style definitions:

<document styles={{
  paragraphStyles: [
    {
      id: "CustomBody",
      name: "Custom Body",
      basedOn: "Normal",
      spacing: { after: 200, line: 276, lineRule: "auto" },
      runProps: { fontSize: 22, fontFamily: "Georgia" },
    },
  ],
}}>
  <section>
    <paragraph style="CustomBody"><run>Styled paragraph</run></paragraph>
  </section>
</document>

Themes

Apply a built-in theme for consistent document-wide styling:

import { corporate } from "docxio";

<document theme={corporate}>
  ...
</document>

See Styles and Themes for details on built-in themes and creating custom ones.

WASM tree limits

The WASM boundary enforces safety limits on the document tree:

Limit	Value
Max sections	1,000
Max blocks	100,000
Max nesting depth	64
Max JSON size	50 MB

These limits prevent runaway memory usage in browser environments. Documents exceeding these limits will produce an error at render time.