About

Pacsmith is an open-source ISO 20022 toolkit for the FedNow® Service: a message library, a local simulator, a send gateway and client SDKs, all Apache-2.0.

Why it exists

1,725 banks and credit unions — 1,155 banks and 570 credit unions had joined the network by the first quarter of 2026. How many of them can send is not a published figure: the Federal Reserve does not release it, and a Fed spokesperson declined to comment when asked; what is reported is that many institutions signed up only to receive. The asymmetry is not an accident — the receive side can be bought as part of a core banking package, while the send side means owning ISO 20022 message construction, profile validation, message signing, 24x7 operation, and the failure mode nobody demos: you sent a payment and no response came back.

That last one is why this project has the shape it does. A sending institution that guesses wrong about an unanswered payment either loses money or sends it twice. Pacsmith takes the position that unresolved submissions are reconciled with a status request and never resent blindly, and builds that invariant into the gateway’s state machine rather than into a runbook.

Who maintains it

Built and maintained by João Bueno (@joaoabuenosi) — a payments engineer who ran Pix point-of-sale middleware in production.

That is the same problem shape as an instant-payment send side in the US: a rail whose settlement is final, running 24x7, with someone on the other end waiting for an answer. Most of the lessons transfer directly — idempotency is not optional, timeouts are a state and not an error, and reconciliation is a product feature rather than an operations chore.

The project is documentation-first on purpose. The Integration handbook is written alongside the code, every claim either sourced from public documentation or demonstrated by something you can run against the simulator.

• Source, issues and roadmap: github.com/joaoabuenosi/fednow-oss
• Security reports: see the security policy — not a public issue
• Contributions: CONTRIBUTING.md

Talk to the maintainer

Until now the only contact address on this site was the one for reporting a vulnerability, which is a poor door to knock on if you simply have a question. So, explicitly: if you are at a bank or a credit union, the following are welcome, and they are what decides what gets built next.

• Evaluation questions — the supply chain, the licence, the disclosure process, or what is genuinely implemented today versus what is still on the roadmap. The Evaluate page is the written answer; anything it does not cover, ask.
• Pilots — standing the gateway and the simulator up against your own environment, and working out what would have to be true before any of it went near production.
• Design partners — the simulator is being packaged as a certification-readiness kit (#79), a local rehearsal of the Customer Testing Program’s scenarios before you book operator time. Institutions that will actually run those scenarios get to shape it.

Two channels, both already in use:

• GitHub Discussions — public, and the better default: someone else is usually asking the same thing.
• Email — joaobuenosi@gmail.com, the address in the security policy, for anything that should not be public.

No support contract sits behind either of them, and there is no vendor relationship on offer: one maintainer answers as soon as they reasonably can. The 72-hour acknowledgement in the security policy is a commitment about vulnerability reports specifically — and those still go through the disclosure process, not through the two channels above.

What this is not

Pacsmith is an independent open-source project. It is not affiliated with, endorsed by or sponsored by the Federal Reserve. “FedNow” is a service mark of the Federal Reserve Banks and is used on this site only to describe, factually, what the software interoperates with. No Federal Reserve branding, imagery or colours are used here, and none of the project’s names or assets should be read as suggesting a relationship that does not exist.

Nor is it certified. Nothing in this repository has been approved for production use by any payment operator, there is no compatibility guarantee, and passing the local simulator or the conformance vectors is a rehearsal — not a substitute for an operator’s own testing programme. It is early development software, offered under a licence that disclaims warranty.

The name

A smith works pacs messages — pacs.008, pacs.002, pacs.028, pacs.004 — the ISO 20022 family this toolkit spends its life shaping. The name belongs to the project, which is the point: the brand is ours, and the service mark stays where it belongs, describing what the software talks to.

Privacy

This site counts page views with Vercel Web Analytics — privacy-friendly and cookieless. It stores no personal data and no IP addresses, writes nothing to your device to do it, and therefore needs no consent banner. It is first-party: both the script and the endpoint it reports to are served from this domain under /_vercel/insights/, never from a third-party host. The only third-party request this site makes is the OpenSSF Scorecard badge on the Evaluate page, which is served by OpenSSF.

This site sets no cookies. Not for analytics, not for anything else.

It does keep exactly two preferences in your own browser, and they are worth naming rather than hiding behind “no tracking”:

• starlight-theme, in localStorage — whether you chose the light or the dark theme.
• sl-sidebar-state, in sessionStorage — which sidebar sections you left open, and where you had scrolled to.

Both are written by the site’s documentation theme so a page looks the way you left it. Neither is a cookie, neither is ever sent anywhere, and neither identifies you. If a third key ever appears, the build fails until this list is updated — npm run check holds the page and the code to each other.

For completeness rather than comfort: the site is hosted by Vercel, so Vercel already serves every request to it. The page-view count adds a number, not a new party.

The software itself is a separate matter and unchanged — it has no telemetry and never phones home. Nothing you run reports back to this project.