Installation

Prerequisites

• Rust (stable toolchain)
• wasm-pack (v0.10+)

Obtaining Dictionaries

Lindera WASM does not bundle dictionaries by default. The recommended approach for browser environments is to download dictionaries at runtime using the OPFS (Origin Private File System) API.

Download from GitHub Releases

Pre-built dictionaries are available on the GitHub Releases page. In browser environments, use the OPFS helpers to download and cache dictionaries:

import { downloadDictionary, hasDictionary } from 'lindera-wasm/opfs';

if (!await hasDictionary("ipadic")) {
    await downloadDictionary(
        "https://github.com/lindera/lindera/releases/download/<version>/lindera-ipadic-<version>.zip",
        "ipadic",
    );
}

See OPFS Dictionary Storage for the full workflow.

Building with wasm-pack

Build the WASM package (the published lindera-wasm npm package is built with the web target):

wasm-pack build --target web

The output is written to the pkg/ directory inside the lindera-wasm crate. wasm-pack also supports other targets (e.g. --target nodejs) if you need a custom build, but the web-target build is what this documentation assumes.

Why the web Target (and Not bundler)?

wasm-pack's default --target is bundler, yet the published lindera-wasm package is deliberately built with --target web. The target names are somewhat misleading, so here is what each one actually produces:

• --target bundler (the wasm-pack default) emits JavaScript that imports the .wasm file as an ES module. This relies on the WebAssembly ESM integration proposal, which is not yet a finalized web standard; in practice the only bundler that understands the output is Webpack with the asyncWebAssembly experiment enabled. The default dates from the era when Webpack was the dominant bundler -- despite the generic name, the output is effectively Webpack-specific. Vite, for example, needs extra plugins (vite-plugin-wasm plus top-level-await support) to consume it.
• --target web emits standards-based code only: the .wasm file is resolved via new URL('lindera_wasm_bg.wasm', import.meta.url) and loaded with fetch + WebAssembly.instantiateStreaming inside an explicit async init function. This runs in browsers as native ES modules with no build step at all, and modern bundlers (Vite, Webpack 5, Rollup) recognize the new URL(..., import.meta.url) pattern and ship the .wasm file as an asset. The one cost is that you must call await __wbg_init() once before using the API.

In short, the bundler target is zero-config for Webpack only, while the web target runs everywhere at the cost of one explicit init call. Up to v5, Lindera published both variants (lindera-wasm-web and lindera-wasm-bundler); v6 consolidates on the single portable build. If you are migrating from lindera-wasm-bundler, see the v5 to v6 migration guide.

Available Feature Flags (Advanced)

For advanced users who want to embed dictionaries directly into the WASM binary, the following feature flags are available. This increases the binary size significantly but eliminates the need to download dictionaries at runtime.

You can combine multiple dictionaries by enabling multiple feature flags:

wasm-pack build --target web --features embed-ipadic,embed-ko-dic

NPM Package Naming Convention

The unscoped lindera-wasm-* prefix is the Lindera project's namespace. If you publish a custom build with embedded dictionaries to npm, use a name under your own scope so it cannot be mistaken for an official package:

@your-scope/lindera-wasm-{dict}

Examples:

• @your-scope/lindera-wasm-ipadic
• @your-scope/lindera-wasm-unidic
• @your-scope/lindera-wasm-cjk

To set the package name before publishing, edit the name field in the generated pkg/package.json. Note that a package with an embedded dictionary redistributes that dictionary, so follow the dictionary's license terms (attribution and so on) as well.

[!NOTE] This project's own release workflow (.github/workflows/release.yml) only builds and publishes a single package to npm -- lindera-wasm, built with wasm-pack --target web and without any embed-* feature. Unscoped dictionary-suffixed names such as lindera-wasm-ipadic are reserved by the project (leftovers from pre-v3 releases, no longer updated) and must not be claimed by third parties; in this documentation they only illustrate what a local build with an embed-* feature (see Available Feature Flags above) would produce.

Installing from npm

The pre-built package is available on npm:

npm install lindera-wasm

Or with yarn:

yarn add lindera-wasm

Because the package is a web-target build, call the default-exported async init function once before using any API:

import __wbg_init, { TokenizerBuilder } from 'lindera-wasm';

await __wbg_init();

This applies both in browsers (native ES modules) and when the package is consumed through a bundler -- modern bundlers such as Vite or Webpack 5 (with the asyncWebAssembly experiment) handle the web-target build directly; see Browser Usage for bundler configuration.

[!NOTE] The npm package does not include dictionaries. Use the OPFS helpers to download dictionaries at runtime. See OPFS Dictionary Storage.