Pricing

Simple pricing. No tricks.

Start free. Stay free if that's enough. Upgrade when you outgrow it — pay only for what you use, nothing more.

Free

$0 forever

Perfect for side projects and small forms.

Get started for free
Recommended

Pro

$19 /month

Cancel anytime. No annual lock-in.

  • Everything in Free, plus:
  • Unlimited forms
  • Unlimited submissions
  • 500 AI credits / month (replenishing)
  • Metered overflow (pay as you go)
  • Priority support
Go Pro
How pricing works

Three things to know. That's it.

Submissions

A submission is one record received and processed. Validation, spam detection, and storage all count as part of the same submission — not separate charges.

AI credits

AI features — intelligent spam, translation, smart replies — use credits. Free gets 50 one-time. Pro gets 500 a month. Standard spam (heuristics, honeypot) uses no credits.

Metered overflow

Go past 500 credits in a month on Pro and we don't cut you off. You pay the per-action rate for anything extra, billed at cycle end.

AI credit rates

What each AI feature costs.

Use your included credits first. Beyond those, these same rates apply as metered billing.

Spam detection

$0.005

per submission

Translation

$0.005

per submission

Smart reply

$0.01

per reply

Worked example

A Pro user with 800 submissions a month, running intelligent spam on all of them and auto-replying to half:

  • 800 × $0.005 = $4.00 spam detection (800 credits)
  • 400 × $0.01 = $4.00 smart replies (400 credits)

Credits used: 1,200. Included on Pro: 500. Metered overflow: 700 credits = $5.00. Final bill that month: $19 base + $5.00 metered = $24.00.

Your numbers are probably different — try the calculator
Common questions

The things you'd want to know before signing up.

What counts as a submission? +
One successful POST to your endpoint that passes validation. Rejected requests — bot traffic, invalid fields, honeypot trips — don't count toward your total. You only pay for what actually lands.
What happens when I hit the 5,000 cap on Free? +
Your form stops accepting new submissions and the endpoint returns a 429. Existing data stays accessible. Upgrade to Pro to remove the cap — it takes effect immediately.
Do AI credits roll over? +
Free credits are one-time and don't expire. Pro credits reset each month at 500 — unused ones don't stack. Anything beyond 500 is metered and billed at cycle end at the rates above.
Can I use Postbox without AI features? +
Yes, all day. Standard spam protection, validation, notifications, the REST API, and MCP all work without touching a single credit. AI is additive, not required.
Can I switch plans anytime? +
Yes. Upgrade is immediate. Downgrade keeps all your data — you'll be asked to pick one form to keep active on Free if you have more than one.
Is my data still mine? +
Always. You own every submission. We process them on your behalf and store them for you. We never sell them. Export anytime via the API.
What happens if I cancel Pro? +
You keep Pro until your current cycle ends, then you drop to Free. Your forms stay. If you have more than one form, we'll ask you to pick one to keep active — the rest sit paused until you come back.
Do you offer refunds? +
Within 14 days of upgrade, yes — just email us. After that, cancel anytime and you won't be billed again.