Install

Run npx next-tongue in a Next.js 16+ App Router project: it detects your locale files, signs you in, lets you pick languages, shows the cost and writes the translated files.

Fact	Value
Requirements	Node 20+, Next.js 16+ (App Router), React 19+
Package	`next-tongue` (MIT); binaries `tongue` and `next-tongue`
Free allowance	50,000 characters, one-time per organisation: unlocked by adding a card (Stripe, no charge; one claim per card), never resets. Until then the API returns `402 card_required` with `details.setupUrl`
Prepaid credits	£25 per 1M characters. Top up £5/£10/£25/£50 or any amount from £5; each purchase expires after 12 months, oldest used first; no automatic top-ups
Engine	OpenAI gpt-4.1-mini, gpt-4o-mini fallback, run server-side

How do I install next-tongue?

npm install next-tongue
npx next-tongue

With no command in a terminal, next-tongue launches the guided wizard. In an existing project, tongue init runs the same flow.

What does the wizard do?

Detect — reads package.json and tongue.config.ts, then finds messages/*.json, locales/{lang}/**/*.json or src/i18n/**/*.ts dictionaries and infers the layout.
Sign in and link — runs device-code login inline, then picks or creates a project.
Source — choose the source language and confirm the glob of key files.
Targets — searchable multi-select of about 130 locales.
Estimate — billable characters and £ cost after cache, lockfile hits and your remaining allowance; explicit confirm.
Translate — streams progress per locale, re-validates ICU locally and writes files.
Summary — strings translated, characters billed, cost and a dashboard link.

Can I run it non-interactively?

Yes. Every prompt has a flag:

tongue init --yes --source en --files 'messages/en/**/*.json' \
  --targets fr,de,es,it,ja,pt-BR --project new:acme-web --max-cost 10

Where do my strings go?

Source strings are sent to Loomlocale for translation and processed under API terms that exclude training. Team plans can process in the EU only. The runtime, compiler, check, extract, export, import, report and migrate stay offline.

Changelog

26 October 2026 — docs published for next-tongue 1.0.0-rc.

Accounts

Create an account at /signup with your email and a password (10+ characters, upper- and lower-case letters and a number), then confirm your address from the email we send. Forgotten it? Use /reset-password. You can change your password any time in Dashboard → Settings. The CLI never asks for your password: tongue login opens /device, where you approve the terminal from your signed-in browser.