Preventing paste in form fields is security theater that actively harms your users. It blocks password managers, forces manual typing of complex passwords, and makes forms slower for everyone - while providing zero actual security benefit.

What's Happening

Some input fields have JavaScript that intercepts the paste event and cancels it, or CSS that disables clipboard functionality. This typically appears on:

• Password confirmation fields ("retype your password")
• Email confirmation fields
• Credit card number inputs
• Verification code fields

The intent is usually to force users to "prove" they typed correctly. In practice, it:

1. Breaks password managers (the primary tool for using strong, unique passwords)
2. Forces users to manually type long, random passwords - leading to errors and frustration
3. Encourages simpler passwords that are easier to type
4. Fails to catch typos anyway (users mistype the same way twice)

Diagnose

DevTools

1. Right-click the problematic input > Inspect
2. In Elements panel, look for onpaste attribute in HTML
3. Check Event Listeners panel for paste listeners
4. Look for CSS user-select: none or -webkit-user-select: none

Quick Console Check

document.querySelectorAll('input, textarea').forEach((el) => {
  const events = getEventListeners(el)
  if (events.paste) {
    console.warn('Paste blocked on:', el, events.paste)
  }
})

Lighthouse Details

The audit "Prevents users from pasting into input fields" lists each offending element with its DOM location and input type.

Fix

1. Remove Paste Prevention

Find and delete the code blocking paste:

Before (bad):

<!-- HTML attribute -->
<input type="password" onpaste="return false">

<!-- Inline handler -->
<input type="email" onpaste="event.preventDefault()">

After (good):

<input type="password">
<input type="email">

JavaScript event listener:

// Bad: Blocking paste
passwordInput.addEventListener('paste', e => e.preventDefault())

// Good: Remove the listener entirely, or just delete this code

2. Remove Confirmation Fields Entirely

The "retype your email" pattern doesn't catch errors anyway. Users who mistype their email will mistype it the same way twice.

Before:

<input type="email" name="email" placeholder="Email">
<input type="email" name="email_confirm" placeholder="Confirm email" onpaste="return false">

After:

<input type="email" name="email" placeholder="Email">

Add email verification by sending a confirmation link. That's actual validation.

3. If You Must Have Confirmation, Allow Paste

If product requirements demand confirmation fields, at least let users paste:

<label>
  Password
  <input type="password" name="password" autocomplete="new-password">
</label>
<label>
  Confirm Password
  <input type="password" name="password_confirm" autocomplete="new-password">
</label>

Both fields allow paste. Password managers fill both. Users with manual passwords can paste into both. Validation happens on submit:

form.addEventListener('submit', (e) => {
  const password = form.password.value
  const confirm = form.password_confirm.value

  if (password !== confirm) {
    e.preventDefault()
    showError('Passwords do not match')
  }
})

4. Fix CSS-Based Blocking

Some implementations use CSS to prevent text selection and pasting:

Before (bad):

.secure-input {
  user-select: none;
  -webkit-user-select: none;
}

After (good):

/* Just remove these properties */
.secure-input {
  /* Let users interact normally */
}

5. Handle Third-Party Form Libraries

Some form libraries or payment processors add paste prevention. Check their configuration:

// Example: Some validation libraries
const form = new FormValidator({
  preventPaste: false, // Disable this
  // ...
})

For embedded payment forms (Stripe, etc.), check their documentation for paste-related settings.

Verify the Fix

1. Reload the page
2. Click into the previously blocked input
3. Paste text (Cmd/Ctrl+V)
4. Text should appear

Test with a password manager:

1. Use the password manager to fill the form
2. All fields should populate correctly

Run Lighthouse - the "Prevents users from pasting into input fields" audit should pass.

Common Mistakes

• Blocking paste only on confirmation field - Both fields should allow paste. Password managers need to fill both.
• Using readonly instead - readonly prevents all input. That's not the same as a functional field that accepts paste.
• Replacing with custom paste handling - Some devs try to "sanitize" pasted content. Unless you're stripping specific characters (like spaces from phone numbers), just allow normal paste.
• Mobile keyboard considerations - Some mobile keyboards have paste functionality that doesn't trigger the standard paste event. Blocking paste may work inconsistently anyway.

The Security Argument

The argument for blocking paste is usually "users should verify what they're typing." Here's why that's backwards:

1. Password managers generate unique, random passwords - Blocking paste means users can't use them, leading to weaker passwords.
2. Mistyped passwords get mistyped consistently - If someone mistypes their email as john@gmial.com, they'll type it wrong both times.
3. Actual security happens server-side - Rate limiting, account verification, and proper authentication matter. Paste prevention doesn't.

NCSC (UK National Cyber Security Centre) explicitly recommends against blocking paste in their password guidance.

Test Your Entire Site

Paste prevention often appears on specific pages: signup, checkout, account settings. Unlighthouse scans your entire site and flags every input with paste prevention, across all forms.

Related

• Best Practices Overview