@mvrx/wbxml

@mvrx/wbxml is a zero-dependency WBXML parser and encoder for Exchange ActiveSync 14.1. It’s independent of AECS-1 and @mvrx/mail — a standalone protocol codec that happens to live in the same monorepo, MIT licensed so it can be embedded anywhere without copyleft obligations (see Licensing).

It works on Cloudflare Workers, Node.js 18+, Deno, Bun, and browsers — no native modules, no Node.js-only APIs.

Install

npm install @mvrx/wbxml

Usage

import { decode, encode } from "@mvrx/wbxml";

// Parse a WBXML binary buffer from an EAS response
const tree = decode(wbxmlBuffer);
console.log(tree.tag); // "Sync"
console.log(tree.children); // [{ tag: "Collections", ... }]

// Build and encode an EAS request
const buffer = encode({
  tag: "Sync",
  namespace: "AirSync",
  children: [
    {
      tag: "Collections",
      children: [
        {
          tag: "Collection",
          children: [
            { tag: "SyncKey", text: "0" },
            { tag: "CollectionId", text: "inbox" },
          ],
        },
      ],
    },
  ],
});

decode() turns a WBXML binary buffer into a plain tree of { tag, namespace?, attributes?, children?, text? } nodes. encode() does the reverse — build the same tree shape and get back a binary buffer ready to send as an EAS request body.

Runtime compatibility

Relationship to AECS-1

@mvrx/wbxml is not part of the AECS-1 specification. It exists because Exchange ActiveSync — a protocol still in wide enterprise use — encodes its XML payloads as compact binary WBXML rather than plain text. If you’re building an inbound pipeline that needs to talk to EAS-based mail systems as well as normalize the resulting messages to NormalizedEmail, you’d typically decode WBXML first with this package, then hand the resulting XML/data to your own EAS response mapper — AECS-1’s parse() (in @mvrx/mail) is scoped to RFC 5322/MIME sources, not EAS payloads directly.