Duplicate Killer – Prevent Duplicate Form Submissions
Prevent duplicate form submissions by email, phone or text. Supports Contact Form 7, Elementor Forms, Forminator, WPForms Lite and more.
5.0
(3 ratings)Will this break my store?
What the WordPress.org registry says about keeping Duplicate Killer – Prevent Duplicate Form Submissions running.
Tested to 7.1.3
Tested against the WordPress branch in use today.4 days ago
At least 10.1 releases a year since launch. WordPress.org only lists versions still available for download, so the real number may be higher.5.6.20
Your host must be running at least this version.5.3
1
A single maintainer. Worth knowing if the plugin is load-bearing for your store.Maintenance & trust
Scored on how Duplicate Killer – Prevent Duplicate Form Submissions is looked after — not on how many stores run it.
91
out of 100Maintenance
35 / 35WordPress compatibility
20 / 20Support responsiveness
Not enough dataMerchant satisfaction
11 / 15Listing transparency
7 / 10Ratings
5.0
3 ratingsDuplicate Killer prevents repeated submissions in WordPress forms. Choose which supported fields must be unique, such as an email address, phone number or text value. When a matching value has already been saved by Duplicate Killer, the plugin blocks the repeated submission and displays your message.
Use it to reduce duplicate leads, repeated contact requests and multiple registrations with the same email address. No CAPTCHA is required for duplicate checks.
Reduce repeated form spam without adding CAPTCHA
Some unwanted submissions repeat the same email address, phone number or other field value. Duplicate Killer can block these repeated values in supported WordPress forms. Optional IP-based limits can also restrict further submissions from the same IP address during your chosen protection period.
Duplicate Killer adds duplicate submission protection, not general bot detection. Spam using new values and different IP addresses may still pass these checks.
When is Duplicate Killer useful?
- Contact forms: reduce repeated requests using the same email address or phone number.
- Registration forms: block another registration with an email address already saved by Duplicate Killer.
- Lead forms: reduce repeated entries before your team follows up.
- Time-based restrictions: allow the same value again after a protection period in minutes, hours or days.
- Multiple forms with PRO: check selected forms within the same supported form plugin.
Duplicate Killer checks submitted values. It does not verify that an email address belongs to the visitor or guarantee one entry per person.
Supported form plugins
Duplicate Killer adds duplicate submission protection to existing forms. It does not create forms. Available fields depend on the integration. The Free version allows configuration of the most recently created form in each supported form plugin.
Contact Form 7: prevent duplicate entries
Block repeated Contact Form 7 submissions using selected fields, such as email, phone or text. Show your duplicate message through Classic Message or Modern Popup Mode.
Elementor Forms: prevent duplicate submissions
Add duplicate checks to forms built with the Elementor Pro Form widget. Duplicate Killer PRO also includes Group Mode for forms that share the same Form Name.
Forminator: control repeated submissions
Choose supported Forminator fields to check for repeated values. Set a protection period when the same value should be allowed again after a certain time.
WPForms Lite: add duplicate-field checks
Use Duplicate Killer with WPForms Lite to check selected fields against entries saved by Duplicate Killer. Visitors receive your configured message when a duplicate is blocked.
Formidable Forms: require unique field values
Apply duplicate checks to supported Formidable Forms fields. For example, check an email field to reduce repeated registrations with the same address.
Ninja Forms: block repeated form values
Add duplicate protection to supported Ninja Forms fields. Choose the values to check and explain blocked submissions with your own duplicate message.
Breakdance Forms: protect your existing forms
Check supported fields in forms built with the Breakdance Form Builder. Configure duplicate protection without replacing your existing form.
Fluent Forms: reduce duplicate leads
Check selected Fluent Forms fields for values already saved by Duplicate Killer. Use this to reduce repeated contact requests or lead submissions.
MetForm: duplicate protection in beta
Add duplicate checks and Modern Popup Mode to supported MetForm forms. Submission details can include links to uploaded files. Test MetForm Pro payment forms and external integrations on a staging site before use.
WordPress form submission limits and IP protection
- Select the fields to check for duplicate values.
- Set duplicate protection periods in days, hours and minutes.
- Configure IP-based submission limits separately.
- Use optional browser cookie protection.
- Review saved submissions in your WordPress dashboard.
- Display the saved submission count with a shortcode.
Field checks and IP limits serve different purposes. Field checks look for repeated values, such as an email address. IP limits restrict submissions from the same IP address, even when the submitted values differ. Configure them separately for your form.
People on a shared network may use the same public IP address. Choose IP restrictions carefully when several visitors may submit from an office, school or household.
Example: block the same email for 24 hours
Select the email field in your protected form and set the duplicate protection period to 1 day. Save your settings, then submit a new email address. Another submission with that email will be blocked during the protection period.
Other enabled rules, such as IP limits, are checked separately.
Classic Message or Modern Popup Mode
Keep a standard duplicate error message or display a custom popup. Modern Popup Mode supports formatted text, links and colors. Preview your popup in the settings before saving. Existing forms keep Classic Message by default.
Free and PRO
The Free version lets you configure the most recently created form in each supported form plugin, with custom protection settings and messages.
Duplicate Killer PRO lets you protect multiple forms with separate settings. Cross-Form Duplicate Protection checks selected forms within the same supported form plugin. Elementor Group Mode groups forms that share the same Form Name.
Use separate rules when your contact form and registration form have different requirements. Use Cross-Form Duplicate Protection when several forms collect entries for the same campaign and should share duplicate checks.
For Elementor sites that reuse forms with the same Form Name, Group Mode helps apply protection across those forms.
WooCommerce duplicate order protection
The Free version also includes duplicate order protection for WooCommerce Classic Checkout, with a 60-second protection window. PRO adds Checkout Blocks support, a configurable protection window and additional reporting tools.
Duplicate Killer focuses on preventing duplicate form submissions and entries. It works alongside spam or CAPTCHA plugins and does not replace them.
Duplicate Killer checks submitted values against saved entries. Performance depends on your hosting, settings and submission history. Modern Popup Mode also uses frontend assets when enabled.
Duplicate Killer helps reduce duplicate leads and contact requests by checking selected email, phone or text fields. Set a protection period and explain blocked submissions with your own message.
Yes. The FREE version protects WooCommerce Classic Checkout from accidental duplicate submissions within a 60-second window.
Duplicate Killer compares selected field values with entries it has previously saved. A matching value can block the submission according to your protection settings and duration. Earlier entries stored only by your form plugin are not automatically imported.
For WooCommerce, a unique order fingerprint is generated from billing email, cart items, order total and currency.
Cookie-based protection uses the visitor’s browser. It does not verify a person’s identity. Clearing cookies or using another browser can change how the visitor is recognized.
Classic Message uses your form plugin’s error display. Modern Popup Mode shows a custom popup for Duplicate Killer duplicate-field messages. It does not redesign your form fields.
Yes. Duplicate Killer supports forms created with the Elementor Pro Form widget. Duplicate Killer PRO also includes Group Mode for Elementor forms that share the same Form Name.
No. Duplicate Killer checks repeated values without requiring a CAPTCHA challenge. CAPTCHA and anti-spam tools address different problems and may still be useful alongside duplicate protection. Test the combined setup with your form plugin and extensions.
Yes. Enable IP-based protection for your protected form and set a duration in days, hours and minutes. This limits form submissions from that IP address; it does not block access to your whole WordPress website.
Check whether IP-based or cookie-based protection is enabled. These rules are separate from duplicate-field checks and may restrict a submission even when the email address is new.
No. Checkout Blocks use a different system (Store API) and require the PRO version.
All WooCommerce duplicate logs stored in the FREE version are automatically used by PRO analytics. No database migration is required.
No. Duplicate order protection and payment processing are different. Duplicate Killer checks checkout submissions, but payment gateway retries and callbacks also depend on WooCommerce and the gateway integration.
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