Duplicate Killer prevents people from submitting the same email, phone number, or text value multiple times in your WordPress forms.
If someone tries to send the same email twice, the second submission is blocked instantly — without CAPTCHA and without changing your form design.
It works silently in the background.
Duplicate submissions can:
Duplicate Killer stops that automatically.
Duplicate Killer works with:
No form redesign required.
That’s it.
Go to:
WordPress Dashboard → Duplicate Killer
Click the tab for your form plugin (for example: Elementor).
You will see a list of detected forms (like in your screenshot):
Example:
Each box represents one form.
Under “Choose the unique fields”, check the field you want to protect:
Most common:
If you check Email, the same email cannot be submitted twice.
In the field:
“Error message when duplicate is found”
Enter something like:
This email has already been submitted!
Save settings.
[email protected][email protected]If it does → it’s working correctly.
You can block duplicates by:
Works per form (PRO) or single form (Free).
Instead of generic errors, you can display:
This email has already been submitted.
PRO allows different messages per form.
You can restrict submissions based on IP address.
Example:
Useful for:
Prevents the same person from submitting the same form twice from the same browser.
This does NOT block different users from submitting the same value (when enabled correctly).
Great for:
The plugin stores protected values safely in your WordPress database.
This is how it checks duplicates.
Detects duplicate submissions across multiple forms on your website.
Instead of checking duplicates only inside one form, the plugin compares data between forms.
Example:
A user submits their email in:
If the same email is used again, the second submission can be blocked automatically.
Best for:
Duplicate Killer allows you to display the total number of unique submissions saved for a specific form.
This is useful for:
The feature works using a shortcode.
[duplicateKiller plugin="elementor" form="FORM NAME.NODEID"]
Your function supports the following attributes:
plugin => required
form => required
prefix => optional
suffix => optional
amount => optional
Let’s break them down.
Defines which form plugin is being used.
Examples:
elementorcontactform7wpformsforminatorninjaformsformidablebreakdanceExample:
plugin="elementor"
This must match exactly the form key shown in Duplicate Killer settings.
Example from backend:
FORM ULTIM.cf2104e
So you use:
form="FORM ULTIM.cf2104e"
Important:
Text displayed before the number.
Example:
prefix="Total registrations:"
Text displayed after the number.
Example:
suffix="people joined"
Adds a custom number to the total.
Useful if:
Example:
amount="50"
If database count = 120
Displayed result = 170
[duplicateKiller plugin="elementor" form="FORM ULTIM.cf2104e"]
Output:
12
[duplicateKiller plugin="elementor" form="FORM ULTIM.cf2104e" prefix="Already registered:" suffix="people"]
Output:
Already registered: 12 people
[duplicateKiller plugin="elementor" form="FORM ULTIM.cf2104e" prefix="Over" amount="100" suffix="applications received!"]
If count = 45
Output:
Over 145 applications received!
The function uses WordPress transients:
set_transient( $transient_key, $count, 30 );
This means:
After 30 seconds, it refreshes automatically.
If:
The shortcode returns:
No data available.
This prevents errors on the page.
You can place the shortcode in:
It works anywhere WordPress shortcodes work.
✔ Use it on event landing pages
✔ Use it to show social proof
✔ Combine with testimonials
✔ Add animation using Elementor for visual impact
Example:
Join over 245 professionals who already registered!
Display Submission Count:
Perfect for small websites with 1 main form.
Ideal for:
Use Duplicate Killer if you:
