GOV.UK Prototype Kit vs Vibe.WithGov

The GOV.UK Prototype Kit is the canonical government-built toolchain for rapid prototyping: a Node.js + Nunjucks project published by the Government Digital Service, used by service teams across UK departments to build clickable journeys for user research. Vibe.WithGov is an independent tool that generates a Prototype Kit project from a plain-English service spec.

Both produce the same kind of artefact — a Node + Nunjucks app using GOV.UK Design System components. The difference is who writes the code. With the Kit you write the Nunjucks templates, Express routes and validation by hand. With Vibe you describe the journey (“an applicant applies for a fishing licence: name, address, date of birth, licence type, payment”) and the same artefact is generated for you.

Side-by-side comparison

When the Prototype Kit is the right call

• Your team already has a developer who knows the Kit, and the journey you need is small enough that hand-coding it is faster than briefing a tool.
• You need full control over the Nunjucks output for an unusual pattern that isn’t in the design system.
• You want a tool that the GDS itself publishes and maintains, with no third-party dependency in your discovery process.
• You want to extend the Kit with custom middleware, integrate it with internal department APIs at the prototype stage, or run it inside an air-gapped environment.

When Vibe is the right call

• The team is a service designer or product manager with no dedicated front-end developer to hand the spec to.
• You need a working journey in front of research participants this week, not next sprint.
• You are exploring two or three competing service designs and want a real clickable comparison rather than wireframes.
• You want the validation, error summary and accessibility patterns wired up correctly the first time, without having to remember which Design System rule applies where.
• You want the prototype hosted on a shareable URL without standing up your own Heroku or fly.io instance.

Can the two be used together?

Yes. The Vibe output is a Prototype Kit project. You can export it as a ZIP, open it in your editor and continue building in the Kit by hand. A common pattern is to generate the first three or four pages of a journey in Vibe to get to a clickable artefact quickly, then drop into the Kit to refine specific pages with unusual interaction patterns. The hand edits round-trip back into Vibe so the AI can pick the work up again when you next want to iterate by conversation.

Neither is for production

The Prototype Kit is explicit on this point and so is Vibe: neither produces code that should be deployed as a live service. Prototypes are clickable mock-ups for user research and service assessment. The route from prototype to production runs through engineering, security review, accessibility audit and the GDS service assessment — regardless of how the prototype was authored.