Stop the same person taking a second free trial

One API call per signup. Allow, challenge or deny, before the account exists.

Start free See how it works

500 free decisions a month. No card.

One person in three disguises, each trying to claim the same free-trial ticket.

Where you read it back

Real screens from a live workspace, fed by the built-in sandbox.

Five kinds of evidence.
None decides alone.

A repeat device is a household. A shared subnet is an office. What moves a signup is how many independent kinds agree.

Five clues—a payment card, phone, envelope, globe and stopwatch—connected to one trial ticket with yellow paper strips. — The accounts a decision links to, and what each was told.

Payment: Card fingerprints from your own Stripe.
Device: A hint that survives cleared cookies.
Email: Plus tags stripped, dots folded, throwaways known.
Network: The subnet, the network type, where it resolves.
Behaviour: The pace of the form, a cold arrival, the hour.

Three answers, and what each one costs you

Abuse is rarely a bot. It is one person with a fresh mailbox and a cleared browser. Blocklists miss them; hard blocks lose real customers.

deny

Send them to a paid plan

Strong evidence of a repeat. Offer the paid plan. The visitor never sees why.

challenge

Ask for one proof

One proof: a card, an email link or a captcha. Real customers clear it and carry on.

allow

Create the trial

Nothing looks like a repeat. Most of your traffic, and it never notices.

Watch one signup become a verdict The same call covers promo redemptions.

A customer holding her first free-trial ticket, framed in yellow.

your first week

Nobody gets turned away on your first day.

New workspaces start in shadow mode: every signup is scored, your app is always told allow. Read a week of what would have happened, then turn enforcement on.

json
{ "decision": "allow", "shadow": true, "wouldBe": "deny", "score": 81 }

An exception in plain English, editable before it saves.

A hand using a pencil to edit a paper rule, with a yellow sheet and a circled correction.

Three steps to live

Read the docs

Next.js
Express
Django
Rails
Laravel
Supabase
Clerk
Auth0
Firebase
Stripe

Put one tag on your signup page
It mints a token and shows nothing. Nothing is decided in the browser.
```
html
<script src="https://onetrial.fly.dev/v1.js" data-key="YOUR_PUBLIC_KEY" async></script>
```

Send the token with the signup

One call from your server. Under 300ms at the median.

typescript
const res = await fetch('https://onetrial.fly.dev/api/v1/decisions', {
  method: 'POST',
  headers: { Authorization: `Bearer ${process.env.ONETRIAL_API_KEY}`, 'Content-Type': 'application/json' },
  body: JSON.stringify({ visitorToken, email, ip, userId }),
});
const d = await res.json();
if (d.decision === 'deny') return showPaidPlanOrSupport();
if (d.decision === 'challenge') return redirect(d.challengeUrl); // trial unlocks on the challenge.completed webhook
createTrial(userId);

Act on one of three answers

Allow, challenge or deny. The reasons are yours, never the visitor’s.

json
{
  "decision": "deny",
  "score": 81,
  "reasons": [
    "D_DEVICE_REPEAT",
    "E_EMAIL_REPEAT",
    "N_IP24_REPEAT"
  ],
  "challengeOptions": []
}

Or let an agent do all three

Detects your framework, writes the env, injects the tag, self-tests the install.

Cursor
Claude Code
Copilot
v0

bash
npx onetrial init

Guides for Next.js, Express, Django, Rails and Laravel.

Everyone gets one.