Firefox Browser Add-ons
  • Extensions
  • Themes
    • for Firefox
    • Dictionaries & Language Packs
Log in
Preview of BreachCheck

BreachCheck by Pixelvault Labs

Check if a password has appeared in known data breaches — privately, using k-anonymity. Includes a secure password generator and strength meter. Nothing you type ever leaves your device.

0 (0 reviews)0 (0 reviews)
Download Firefox and get the extension
Download file

Extension Metadata

Screenshots
About this extension
BreachCheck — has your password been breached?

Billions of passwords have leaked in data breaches. If yours is one of them, attackers can log in as you anywhere you reused it. BreachCheck tells you in one click — without ever exposing your password.

PRIVATE BY DESIGN (K-ANONYMITY)
Your password is hashed with SHA-1 on your device, and only the FIRST 5 characters of that hash are sent to the free HaveIBeenPwned Pwned Passwords API. The API returns ~800 candidate hashes; your device compares them locally and reports the result. The password — and even the full hash — never leaves your device. It is never stored, and the field is cleared after every check.

WHAT YOU GET
- One-click breach check against 15+ billion breached passwords
- Password generator: 12–32 characters, cryptographically random (crypto.getRandomValues), numbers/symbols toggles, click-to-copy
- Local strength meter: entropy-based, no libraries, no network
- Check history: date + outcome only (never the password), clearable

HONEST WORDING
"Not found" means no known breach contains the password — it is not a guarantee of safety. We never claim a password is "safe".

PERMISSIONS — MINIMAL
- storage: keeps your check history (outcome only) on your device.
- api.pwnedpasswords.com: the anonymous 5-character hash-prefix lookup.
No content scripts. No page access. No remote code. No accounts, no tracking, no analytics.

Free forever. Made by Pixelvault Labs.
Rated 0 by 0 reviewers
Log in to rate this extension
There are no ratings yet

Star rating saved

5
0
4
0
3
0
2
0
1
0
No reviews yet
Permissions and data

Optional permissions:

  • Access your data for api.pwnedpasswords.com

Data collection:

  • The developer says this extension doesn't require data collection.
Learn more
More information
Add-on Links
  • Support Email
  • Copy add-on ID
Version
1.0.0
Size
41.02 KB
Last updated
5 days ago (Sep 27, 2026)
Related Categories
  • Privacy & Security
License
All Rights Reserved
Privacy Policy
Read the privacy policy for this add-on
Version History
  • See all versions
Add to collection
Report this add-on
Go to Mozilla's homepage

Add-ons

  • About
  • Firefox Add-ons Blog
  • Extension Workshop
  • Developer Hub
  • Developer Policies
  • Community Blog
  • Forum
  • Report a bug
  • Review Guide

Download

  • Download Firefox
  • Windows
  • macOS
  • iOS
  • Android
  • Linux
  • All

Latest Builds

  • Nightly
  • Beta

Firefox for Business

  • Enterprise

Community

  • Connect
  • Contribute
  • Developer

Follow

  • Instagram
  • YouTube
  • TikTok
  • Bluesky
  • Podcast
  • Privacy
  • Cookies
  • Legal

Except where otherwise noted, content on this site is licensed under the Creative Commons Attribution Share-Alike License v3.0 or any later version.