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HTML parser and serializer.


Version published
Weekly downloads
increased by0.15%

Weekly downloads



Welcome to [email protected]! ✨ This is a huge release with many changes, features and fixes.

From an organisational perspective, the most important change is that parse5 is now maintained by a team, consisting of James (@43081j), Titus (@wooorm) and me (@fb55). We come from three projects that rely on parse5 — namely Cheerio, rehype, and Lit.

We need your support to continue the project! If you care about parse5, please support us financially on OpenCollective.

Headlining features of this release are ES Modules, TypeScript, and performance improvements: 7.0.0 is 45% faster than 6.0.1 with default options, and 167% faster with location information enabled (for the bench/perf benchmark, on an M1 Mac). Version 7.0.0 is a revamp of every part of the library. There are too many changes to list them all here, so here is a high-level overview:

Breaking: ESM

All of parse5’s packages are now ECMAScript Modules. We are providing dual packages for parse5 and parse5-htmlparser2-tree-adapter for now (see and

To migrate, please read this Gist on how to update. Note that private internals are no longer available; instead, everything that you need should be imported from the main package.

Implemented by @43081j in #351

Breaking: TypeScript

The codebase has been ported to TypeScript. This helped uncover a number of subtle logic bugs, such as dc4e269022ebbae0767d8f790a29d6be1835fe1e, b4b5d4ad6f90b3c9fd03a90e2ed5267929979a11, or a0aff9578bb44511bc169c1d7f9e2f2780f7f8a0. TypeScript also helps us refactor with confidence and a lot of the changes in this release would have been much harder to do without it.

To migrate, please remove @types/parse5* as we now ship our own types.

Implemented by @fb55 in #362

Potentially breaking changes

  • parse5 was caught up with the HTML spec, and parsing results might differ in edge-cases (,
  • The parse5-serializer-stream package was removed
    • To migrate, use the serialize function exported by parse5.
  • The rewriting stream now splits very long text sections ( and doesn’t escape text in special tags anymore (#434). If you worked around these issues before, you might have to update your code.
  • The htmlparser2 adapter now uses domhandler’s node interface ( by @TrySound)
    • The format of the tree nodes has changed slightly; eg. some previous properties are now getters and setters, and vice versa.

If you are using deep imports for any parts of the codebase, you will likely encounter some breakages:

<details><summary>Show internal changes</summary>
  • The tokenizer now uses the state machine pattern from htmlparser2 5d7a780 (#362)
  • The token queue was replaced with callbacks (,,
  • The OpenElementStack now uses callbacks
  • Mixins were removed (as part of #362)
    • Location tracking now has a substantially lower overhead
  • getNextToken was removed
  • The parser’s _bootstrap method was removed
  • We now drop chunks from the tokenizer right after they are emitted
  • The serializer is no longer a class; instead, different serializer functions call on each other
  • parse5 now uses the entities module for encoding and decoding entities, sharing maintenance & optimisation work with projects such as htmlparser2 (2b92054 (#362),
    • entities adopted a variant of parse5’s approach of decoding entities. As a result, decoding performance is equivalent, while memory consumption is slightly lower.

Other changes

  • minor add hooks for stack events to tree adapter interface #385
  • minor add support for fragments in parse5-parser-stream #487
  • minor add serializeOuter (like .outerHTML), scriptingEnabled option #383
  • patch fix parsing of << in comments parsed wrongly as <! (#326)
  • patch fix position of endTag for mixed-case foreign elements (#353)
  • patch fix end position of html, body (#436)
  • docs: parse5 has a new documentation website at #443

New Contributors

Thanks @anko, @TrySound, @samouri, @alan-agius4, and @pmdartus!

Full Changelog:





HTML parser and serializer.

npm install --save parse5

📖 Documentation 📖

List of parse5 toolset packages


Online playground




What is parse5?

HTML parser and serializer.

Is parse5 popular?

The npm package parse5 receives a total of 26,722,733 weekly downloads. As such, parse5 popularity was classified as popular.

Is parse5 well maintained?

We found that parse5 demonstrated a healthy version release cadence and project activity. It has 4 open source maintainers collaborating on the project.

Last updated on 20 Apr 2022


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