histos

Pack any web app WASM(Rust/C), HTML, CSS, JS, into a single self-contained .html file.

No server. No CDN. No internet required at runtime. Open directly in a browser.

First class wasm-pack support for Rust and SINGLE_FILE=1 for Emscripten/C.

repo

How it works

histos reads a YAML config describing your web assets and weaves together one portable index.html:

• WASM binaries are brotli-compressed, base64-encoded, and stored in <pre> tags
• A bundled runtime decoder unpacks the WASM at load time
• Decoded WASM is cached in IndexedDB — subsequent loads are instant
• CSS files are fetched and inlined as a single <style> block
• JS and HTML fragments are inlined verbatim
• Favicons are base64-encoded SVGs

The result is a fully offline, browser-runnable application in one file.

Install

cargo install histos

To compile WASM from source during packing, also install wasm-pack:

cargo install wasm-pack

Quick start

# config.yaml
pack:
  metadata:
    title: "My App"
  css:
    - ./styles/main.css
  runtime:
    enabled: false

histos config.yaml
histos config.yaml --output ./dist/index.html

WASM app example

pack:
  metadata:
    title: "My WASM App"
    author: "Jane Doe"
    description: "A Rust/WASM app packed by histos"

  favicon:
    - ./assets/icon.svg

  css:
    - https://cdnjs.cloudflare.com/ajax/libs/normalize/8.0.1/normalize.min.css
    - ./styles/app.css

  wasm:
    app:
      path: ./my-wasm-project        # parent of pkg/
      id: "bin-wasm-app"             # must match default runtime expectation
      compile_wasm: false            # set true to run wasm-pack automatically
      compression: "brotli"

Config reference

Full schema with examples: llms.txt

Common pitfalls

• id must be "bin-wasm-app" when using the default runtime — core.js looks for this exact ID
• compression: "brotli" requires runtime.decoder: true (the default) — or the WASM can't be decoded
• metadata: not meta: — the YAML key is metadata
• Paths are relative to CWD where histos is invoked, not the config file location

Library API

histos is also usable as a library crate for programmatic HTML packing:

use histos::{PackConfig, HistosResult};

#[tokio::main]
async fn main() -> HistosResult<()> {
    let mut config = PackConfig::new();
    config.set_metadata("My App", "Jane Doe", "An offline WASM app", "");
    config.add_style("https://example.com/style.css");

    let packed = config.build().await?;
    packed.save_to_file("index.html").await?;
    Ok(())
}

License: MIT