Web Integrations

Twilic ships npm packages that encode and decode binary request and response bodies for common JavaScript web stacks. All integrations use the same MIME type and @twilic/core codec.

Content type

Every package exports TWILIC_CONTENT_TYPE:

application/vnd.twilic

Send and expect this Content-Type header on Twilic payloads. Integrations reject or skip decoding when the header does not match (configurable with requireContentType: false on parsers).

Use stateless Dynamic or Batch profiles for HTTP request/response. Stateful session compression requires a persistent ordered channel and is not appropriate for typical HTTP APIs. See FAQ — Can I use Twilic over HTTP?.

Packages

Package	Use with
@twilic/express	Express middleware
@twilic/fastify	Fastify plugin
@twilic/hono	Hono middleware
@twilic/axios	Axios interceptors
@twilic/fetch	fetch helpers

All packages depend on @twilic/core. Install the integration package plus its framework peer dependency.

Express

pnpm add @twilic/express express @twilic/core

import express from "express";
import { twilicParser, twilicSend } from "@twilic/express";

const app = express();

app.post("/users", twilicParser(), (req, res) => {
  twilicSend(res, { ok: true, received: req.twilicBody });
});

Do not mount express.json() before Twilic routes on the same path, or the request body stream will already be consumed. Use a dedicated router or place twilicParser() only on routes that do not use JSON body parsing.

Fastify

pnpm add @twilic/fastify fastify @twilic/core

import Fastify from "fastify";
import { twilicParser, twilicPlugin, twilicReply } from "@twilic/fastify";

const app = Fastify();

await app.register(twilicPlugin);

app.post("/users", { preHandler: twilicParser() }, (request, reply) => {
  return twilicReply(reply, { ok: true, received: request.twilicBody });
});

// or use the reply decorator:
app.get("/ping", (_request, reply) => reply.twilic({ pong: true }));

Hono

pnpm add @twilic/hono hono @twilic/core

import { Hono } from "hono";
import { twilicParser, twilicResponse } from "@twilic/hono";

const app = new Hono();

app.post("/users", twilicParser(), async (c) => {
  const input = c.var.twilicBody;
  return twilicResponse(c, { ok: true, received: input });
});

Axios

pnpm add @twilic/axios axios @twilic/core

import axios from "axios";
import { createTwilicAxios } from "@twilic/axios";

const client = createTwilicAxios(axios.create());

const { data } = await client.post("/api/users", null, {
  twilicBody: { id: 1n, name: "alice" },
});

Set twilicResponse: false on a request when you expect a non-Twilic response body.

Fetch

pnpm add @twilic/fetch @twilic/core

import { init } from "@twilic/core";
import { twilicFetchJson } from "@twilic/fetch";

// In the browser, initialize the WASM backend once before calling helpers.
await init({ prefer: "wasm" });

const data = await twilicFetchJson("/api/users", {
  method: "POST",
  twilicBody: { id: 1n, name: "alice" },
});

On Node.js, @twilic/core selects the N-API backend by default and init() is still recommended before first use.

Custom codec

Each integration accepts an optional codec object with encode and decode functions. Use createTwilicExpress, createTwilicFastify, createTwilicHono, createTwilicAxios, or createTwilicFetch when you need a custom @twilic/core configuration.

Related

• JavaScript / TypeScript SDK
• Twilic CLI — encode and decode from the terminal
• Cookbook — API Response with Repeated Structure
• Examples — HTTP Round-Trip — Express / Hono / Fastify + fetch / Axios