What we looked at
The email you typed, your IP address, and a few signals from your browser. We check them against public blocklists and our own sending history.
ShieldShiba. A captcha that checks the email, not traffic lights.
Stop fake sign-ups before they reach your list. Free, and your visitors never solve a puzzle.
Type an email to see it verify
ShieldShiba
Why was I checked?
The site you were on uses ShieldShiba to keep bots and fake accounts out. You didn't do anything wrong. It took about a second.
What we keep
The email's domain and a one-way hash of the address. Never the address itself. Plus the IP, the browser name, and the result.
What we don't do
No puzzles and no traffic lights. Your browser solves a small math problem in the background in about a second.
If you were blocked
We never say why on screen, so bots can't learn from it. The site owner can see the reason. If you think it's a mistake, contact them.
What it blocks.
Invalid email
Addresses that aren't well formed, and domains with no mail server.
Temporary email
Disposable and throwaway inbox domains.
Spam blocklists
Domains and IPs listed by StopForumSpam.
Abusive IPs
IPs reported on AbuseIPDB, Tor exit nodes, and data-center IPs. You can allow data centers per site.
Bounces across PostShiba
Addresses that hard-bounced or complained with more than one PostShiba sender. Only we can see this.
Scripted browsers
Headless browsers, curl, webdriver, and forms filled faster than a person can type.
Free webmail
Optional per site. Turn it on for B2B sign-ups that should use a work address.
Token reuse
Each pass is tied to one email, used once, and expires in five minutes.
Add it in three steps.
-
1
Create a site key
In your PostShiba account, open Security, then ShieldShiba. Add the hostnames you'll embed on.
-
2
Embed the widget
Add the script and a <shield-shiba> tag next to your email field.
-
3
Verify on your server
POST the token, the email, and your secret key. Accept the sign-up on good_boy.
<script src="https://postshiba.com/shield/v1/widget.js" async></script>
<form action="/signup" method="post">
<input type="email" name="email" id="email">
<shield-shiba sitekey="ss_pk_..." email-field="#email"></shield-shiba>
<button>Sign up</button>
</form>curl -X POST https://postshiba.com/shield/v1/verify \
-H 'Content-Type: application/json' \
-d '{"secret":"ss_sk_...","token":"...","email":"jane@acme.com"}'
{
"success": true,
"verdict": "good_boy",
"reasons": [],
"email": "jane@acme.com",
"hostname": "acme.com",
"created_at": "2026-09-23T05:12:44Z"
}Free for now.
Create a PostShiba account and add your first site key.