Build an extension people pay for

ExtensionStart is a starter kit for browser extensions that charge money, sold as source code for $99 once. It is a complete extension (WXT, React 19, Tailwind CSS 4, TypeScript) with Google and email sign-in, billing through Stripe, Polar, or Paddle, a paywall that follows Chrome Web Store policy, a Firebase or Supabase backend, a website template, and 218 automated tests. You build your feature on top.

TypeScript and React. You do not need to know Manifest V3, OAuth, webhooks, or store policy: ExtensionStart ships those parts built and tested, and the setup wizard configures them. It is not a no-code tool. If you work with an AI coding agent, the repository's AGENTS.md gives it the architecture and the rules, so it can build features the way the kit expects.

Yes, everything except the code itself. The documentation is public and complete: setup, every guide, and a paywall builder you can click through. The demo page shows each screen of the extension in both themes, and the demo website is the website template as you get it. After purchase, the 30-day refund covers the rest.

Check the evidence instead of the pitch. ExtensionStart has 197 unit tests and 21 end-to-end tests that load the built extension in Chromium, one of which stops the background service worker mid-session and checks that nothing is lost. TypeScript runs in strict mode with any banned, and every push runs the typecheck, lint, all tests, and a scan of the built extension for remote code. The documentation shows the architecture of every part.

WXT is the framework ExtensionStart is built on, and it handles the build: manifests, hot reload, store zips. What you pay for is everything a paid extension needs on top of it: sign-in that works inside an extension, checkout with entitlements written by your server, the paywall and its store-policy checks, the backend, store release automation, and the tests that keep all of it working. The comparisons with WXT, Plasmo, Extro, and ExtensionFast go through it line by line.

You can, and the code will look right. The parts that break a paid extension show up only in use: sign-in lost when the browser stops the background worker, a paid plan the extension can grant itself, a paywall a store reviewer rejects. ExtensionStart has those parts built and covered by 218 automated tests. Your agent then writes your feature on top, with AGENTS.md giving it the rules.

Yes. ExtensionStart is a complete extension rather than a library, so you move your feature into it: your UI goes into the popup's Home tab or the side panel, your content script sits next to the kit's, and each paid action calls one access check. Build your feature walks through it. The result ships as an update to your existing store listing.

Monthly and yearly subscriptions, a lifetime one-time purchase, credit packs, and a subscription with monthly credits. On top of any of them: free limits per feature (such as 10 per day), a free trial with or without a card, and when to show the upgrade prompt. The setup wizard offers six ready recipes, and one config file holds the whole decision. Prices live in your payment provider's dashboard, so changing one needs no new release.

Stripe, Polar, or Paddle, one per deployment, chosen in the setup wizard. Polar and Paddle are merchants of record: they collect and pay sales tax and VAT for you, and they pay out to many countries where Stripe does not accept sellers. With Stripe you are the seller, and one setting turns on Stripe Tax at checkout. The payment provider guide compares fees and tax handling.

Not to get a paid plan. Paid access is written by your server when the payment provider confirms a payment, never by the extension; credits are spent on the server, and a card trial is allowed once per account. A paying user who reinstalls or switches browsers signs in and gets their plan back. Free-use counters and trials without a card live in the browser, so a reinstall restarts them; the kit also records every use on your server, ready for a server-side limit where one protects real costs.

No. ExtensionStart supports Firebase (Auth, Firestore, Cloud Functions) and Supabase (Auth, Postgres with row-level security, an Edge Function). The setup wizard asks which one you want and removes the other from your copy. Both serve the same API with the same security model, so the rest of the kit does not change.

No, the setup wizard removes them. Choose a free extension and it deletes billing and the paywall; answer no to the side panel and the side panel goes; pick Firebase or Supabase and the other backend is deleted, and so is the code for the payment providers you did not pick (Stripe always stays). Their files, settings, and browser permissions go with them, and the wizard typechecks what remains.

Chrome and Edge on Manifest V3, and Firefox, from one codebase. Each browser gets its own build, and features that exist only in Chromium browsers, such as the side panel, are switched off in the Firefox build. Pushing a version tag builds all three and, after you approve the release, submits them to the Chrome Web Store, Firefox Add-ons, and Edge Add-ons. Safari is not supported.

With Google or with email and password, including password reset. Free features work without an account, and an optional guest mode gives each install an account that becomes the user's own when they sign in, with nothing lost. Sign-in is asked only when it is needed: in front of a purchase, or on a feature you mark as account-only.

No kit can promise approval, because reviewers also judge your listing and your feature. ExtensionStart removes the rejection causes that come from the plumbing. Free features work on a fresh install without an account (Yellow Magnesium). CI scans the built extension for remote code (Purple Potassium), and nothing is obfuscated (Blue Argon). Every permission comes with its justification for the store form (Blue Lithium). Every paywall can be closed, and a setup with no free feature fails to build until you mark it paid-only, which also writes the disclosure your listing needs. The rejection codes guide covers the rest.

Yes. One AGENTS.md (read by Claude Code, Cursor, and Codex) holds the architecture map, the Manifest V3 pitfalls, and the definition of done. 6 tested prompts cover the common jobs, such as adding a feature, a permission, or a store submission, and a preconfigured Chrome DevTools MCP server lets an agent check its work in a live browser.

An invite to the private GitHub repository, sent to the GitHub account you enter after checkout. It holds the extension, the backend for Firebase and Supabase, the billing code for Stripe, Polar, and Paddle, the setup wizard, a website template with a help center and privacy and terms pages, CI and store release workflows, and the test suite (197 unit tests and 21 Playwright e2e specs). The documentation is public.

About 10 minutes from clone to a signed-in extension that takes a test payment. One command, pnpm create extstart, runs the setup wizard: it names the extension, creates your Firebase or Supabase project, and sets up your products in Stripe, Polar, or Paddle. The few console clicks no command can do, it prints as a checklist with a link to each screen. The setup page lists what to have ready.

Yes, $99 once, with no subscription and nothing more to ExtensionStart. The services your extension runs on are your own accounts and bill you directly: your payment provider takes its fee from each sale, Firebase and Supabase are free to start and charge for usage beyond their free tiers (deploying on Firebase needs its pay-as-you-go plan, which asks for a card), and the Chrome Web Store charges a one-time $5 developer registration fee. The payment provider guide lists each provider's fees.

Yes. Stripe emails an invoice with your receipt after checkout. A business can enter its tax ID at checkout, and the invoice shows it. Sales tax or VAT is worked out at checkout from your address.

Client work, yes: build and sell as many extensions as you like, for yourself or for clients, closed source and without attribution. A license covers one developer, so a team buys one per developer who works in the code; for five or more, email for volume pricing. You cannot resell or publish the kit itself. The license has the full terms.

Updates land in the same private repository, with no renewal fee, and the changelog lists each release. You bring the ones you want into your project with git. Fixes for browser and store changes come before new features. If ExtensionStart is ever discontinued, you keep the repository and the source; nothing in your extension depends on a server of ours. The updates page has the details.

A 30-day money-back guarantee. Email support@extensionstart.com within 30 days of purchase for a full refund; repository access ends with the refund. The refund policy has the details.

Start with the documentation: every part of the kit has its own guide, and the publishing section covers store submissions. For anything else, email support@extensionstart.com.