SimpleWebAuthn: passkey plumbing for people who would rather not write it

Two packages, one job

SimpleWebAuthn is described as WebAuthn, Simplified, and a collection of TypeScript-first libraries for simpler WebAuthn integration. The project has 2,359 stars, 203 forks, six open issues, an MIT license, and its last push was 2026-09-25. The homepage is simplewebauthn.dev.

Two packages are maintained in the repository: `@simplewebauthn/server` and `@simplewebauthn/browser`. The split is the one you would guess. The browser package is the code that runs in your user's browser, generating the options object for a ceremony and translating the authenticator's response into a plain object your server can receive. The server package is the code that validates a registration response, verifies an authentication assertion against stored credential data, and returns results your application logic can act on.

The word complimentary in the README is worth pausing on, because it points at the actual difficulty. WebAuthn is not hard because the cryptography is exotic. It is hard because the protocol has two halves, a ceremony state machine that spans a page load, and a set of options objects whose field names must match exactly on both ends. The two packages exist so that neither half has to be written from scratch.

The repository also ships an `example/` directory described as a single-file Express server plus a few HTML files. The README's claim about it is specific: combined with the packages, it is close to all it takes to get up and running. That is a useful claim to test, because a passkey demo you can run in one file tells you more about integration friction than any amount of documentation.

Publishing to two registries and running on four runtimes

SimpleWebAuthn can be installed from NPM and from JSR, in Node LTS 22.x and higher projects, in Deno v2.4.x and higher projects, and in other compatible runtimes including Cloudflare Workers and Bun. Both registries carry scoped packages, and the README links both badges, so the choice of registry is a per-project decision rather than a philosophical one.

The supported versions policy is stated more precisely than most. For Node, the project targets LTS releases in Active and Maintenance mode, referencing Node's own release schedule page. For Deno, it targets SemVer minor releases such as `2.4.x` for up to one year after their release, referencing the Deno releases page. Written that way, the policy tells you something actionable: when a runtime's support window closes, this library will move on, and you will be the one upgrading.

The topic list on the repository is where the packaging picture gets interesting. Alongside `webauthn`, `passkeys`, `fido`, `node`, `deno`, `denoland`, `browser` and `typescript`, there are three module format topics: `commonjs`, `esm` and `umd`. Publishing CommonJS, ESM and UMD builds means the packages can be consumed by bundler-based toolchains, by Node projects that have not finished migrating to ESM, and by a plain script tag in an older build pipeline. Three formats is more surface to keep correct, and it is also the reason adoption does not stall on module system.

Note the cloud runtime in that list. Cloudflare Workers has no Node process and a different module model, so a library that claims support there has to avoid Node built-ins in its hot paths. If your server runs somewhere exotic, that claim is worth testing against your actual runtime before you commit to it.

Two security releases in three weeks

The recent release history is the most informative part of this repository, because it shows what the maintainer considers in scope.

On 2026-09-05, v14.0.1 added the ability to verify attestation statements using PQC algorithms. Post-quantum cryptography in a passkey library is not decorative: attestation statements are the part of registration where the authenticator tells the server something about itself, and supporting newer algorithm families there means the verification path grows rather than being hard-coded to a small set.

On 2026-09-13, v14.0.2 shipped a fix for a CVSS v3 Moderate, scored 5.4, vulnerability in `@simplewebauthn/server`, tracked as GHSA-2g3p-m8c9-hhwh. The change is described as revamping certificate revocation logic to only cryptographically verify and process CRLs from certificates that chained back to an RP-chosen trust anchor. Read that sentence carefully. The prior behaviour was willing to trust and act on revocation lists whose chain you did not control, which means an attacker who could influence which CRL got processed could shape the outcome. Constraining CRL processing to chains terminating at a trust anchor the relying party selected closes that path.

On 2026-09-25, v14.0.3 made PQC support lazily evaluated. The stated reason is that this delays Node from emitting its PQC warnings from process start until a method that checks for PQC support is actually called. Small change, sensible reason: warning noise at startup trains people to ignore warnings.

Three releases, twenty days, one advisory. That is a healthy pace for a security-critical library, and it is also the argument for reading release notes rather than only watching for major version bumps.

TypeScript source, Deno toolchain, mise for versions

The contradiction here is real and worth naming, because it looks like a mistake and is not.

The repository description says TypeScript-first, and GitHub's language badge says TypeScript. That is accurate about the source language and about what gets published. But development requires Deno v2.4.x, the root has a `deno.json` and a `deno.lock`, there is a `deno/` directory for workspace tasks, and every test command in the README is a Deno task. On top of that sit `mise.toml` and `mise.lock`, which is mise pinning tool versions for whoever runs the commands.

So the build and test runtime is Deno, and the source language is TypeScript, and those are not in conflict. Deno runs TypeScript natively and can publish to both NPM and JSR from one source tree, which is precisely why a project that wants to ship to two registries would reach for it. TypeScript is the language; Deno is the tool; mise is the version manager for whatever else a contributor has installed locally.

The test workflow is documented concretely. Set up dependencies with:

deno install

Then run each package's suite:

cd packages/server/ && deno task test

Watch variants exist as a `test:watch` series. Coverage reporting needs one extra dependency, `genhtml`, which the README tells you to get with `brew install lcov` on macOS, and then:

deno run test:coverage

That last one runs the tests and then hosts a coverage report at `http://127.0.0.1:8000`. Pinning genhtml as a separate requirement rather than bundling it is the right call, since coverage tooling changes faster than the library does.

Not open to contributions, but open to issues

The contributions section is three sentences long and says something you should know before you plan around this library: the project is not currently open to external contributions.

What follows is a request for issues, and a request for detailed ones, with a link to an issue template and an instruction to fill it out with as much information as possible. The same applies to feature requests and to suggestions about existing features. So the support model is single-maintainer triage with no inbound pull requests.

This is a legitimate model for a library like this. Security-critical, standards-tracking, and heavily dependent on browser behaviour, it is exactly the kind of project where a wide contributor surface creates review burden faster than it creates value. The author is also the person most likely to get a WebAuthn specification change right on the first pass.

The practical consequences for you are concrete. You cannot send a patch, so a missing method means either a feature request or a fork. Your upgrade path is one person's judgement about what is safe to change in a major version. And you are dependent on that person continuing to work, which the sponsorship section addresses directly.

That section names a Platinum sponsor, Auth0 by Okta, and a Gold sponsor, Authsignal, with a link to the author's GitHub sponsors page. Commercial sponsorship from two authentication vendors is a reasonable signal about maintenance economics, and it also means the roadmap will naturally lean toward what paying users need. It is not a red flag. It is just context you would want if you were evaluating this for something load-bearing.

Two smaller files in the tree are worth noticing. `HANDBOOK.md` at the root suggests accumulated institutional knowledge beyond the docs site. `whatGotUpdated.ts` is a script, presumably for drafting release notes, which is the kind of small automation a solo maintainer writes and never mentions. And `.git-blame-ignore-revs` exists, which means the history has been rewritten at least once, probably for formatting sweeps.

Editorial conclusion

SimpleWebAuthn exists because WebAuthn has a shape problem, not a difficulty problem. The specification is careful and widely implemented, but the flow requires the server to hold a challenge, hash the right things in the right order, verify a signature against a stored credential, and answer with the exact JSON shape the browser helper expects, and every one of those steps is a place a hand-rolled implementation goes subtly wrong. Two packages, one server-side and one browser-side, remove that whole category of mistake and let you treat registration and login as ordinary API calls. The cost is dependency and governance: this project is not currently open to external contributions, so you are choosing to track one maintainer's release cadence rather than a community's, and a moderate severity advisory inside that cadence is the reason you should read release notes rather than only watch for majors. On runtime support, be honest about what you need: the browser package is what ships to your users, and the server package runs wherever your server runs, including Cloudflare Workers, which is a real constraint if you also depend on Node built-ins elsewhere. Read the docs at simplewebauthn.dev/docs, run the example server, and if you need attestation formats or client extension outputs the packages do not expose, you will be reaching for the underlying library anyway.

Frequently asked questions

Official sources

1. License: MIT
2. MasterKale/SimpleWebAuthn on GitHub
3. Project website
4. README
5. Releases