According to #156, using parse5 in the browser with browserify/webpack is fine. However parse_stream.js causes problems bundling in some environments because stream is a node.js package. And hacks like installing stream don't work because that ancient hack doesn't export Writable.

Non-node environments don't have a use for streams anyways, so it would probably be best if parse5 used the "browser" field in package.json to exclude stream related parts of parse5 from the browser bundled version.