How to Check if Your Password Was Leaked
If you've used the internet for more than five years, statistically one of your passwords has appeared in at least one data breach. The question isn't 'have any of mine leaked' — it's 'which ones, and have I changed them since?' This guide shows how to check safely using k-anonymity, so you never have to send your real password to a third-party service.
Step-by-step
- 1
Understand k-anonymity (so you trust the method)
Modern password-leak checks use a clever protocol: you compute SHA-1 of your password locally, send only the first 5 characters of the hash to the server, and the server returns all leaked hashes starting with those 5 chars. You then check locally whether your full hash is in that list. The server never sees your password or full hash.
Tools:Read about k-anonymity - 2
Use Have I Been Pwned Passwords (or Skopio)
Have I Been Pwned's free Pwned Passwords API uses k-anonymity. Visit haveibeenpwned.com/Passwords. Skopio integrates the same protocol with additional context (which breaches, when).
Tools:Have I Been Pwned Passwords, Skopio Password - 3
Check each of your old passwords
Make a mental or paper list of passwords you've used in the last 10 years (yes, even ones you've abandoned — recycled passwords are the #1 attack vector). Check each one. Don't worry, k-anonymity protects you.
Tools:Personal password log - 4
Replace any leaked passwords NOW
If a password appears in any breach, attackers have it. They'll try it on your other accounts. Change it on every site where you used it. Use a password manager (1Password, Bitwarden) to ensure unique passwords per site going forward.
Tools:1Password, Bitwarden, KeePassXC - 5
Set up breach monitoring for the future
Skopio breach-watch and Have I Been Pwned both offer free email-monitoring: register your email, get notified when it appears in a new breach. Catches future exposures.
Tools:HIBP notify-me, Skopio breach watch
- •Never paste your password into a search engine or random website. Use only k-anonymous tools (HIBP, Skopio).
- •If a password appears 100,000+ times in breaches, attackers literally have a list of users-of-this-password. Even if the leak wasn't from your account, the password is dead.
- •Reusing passwords is the single biggest mistake. A unique password per site means one leak doesn't compromise everything.
ينفّذ Skopio كلّ هذا في استعلام واحد
أوّل بحث كلّ يوم مجاناً. بدون بطاقة.
Frequently asked
Is it safe to enter my password into a checker?+
Only if the checker uses k-anonymity (HIBP, Skopio). Never enter your password into a tool that doesn't explicitly document the k-anonymity protocol.
What if my password is in a breach but I changed it years ago?+
Then it's safe — assuming you also stopped using that password elsewhere. The risk is only if you're currently using a leaked password.
Are leaked-password checkers free?+
Yes. HIBP Passwords API is free for individual queries. Commercial use of the API has rate limits or paid tiers.
Should I check just my main password or all of them?+
All. Recycled passwords are the #1 risk. Even old throwaway passwords matter if you reused them.
Does Skopio store the passwords I check?+
No. Skopio uses the same k-anonymity protocol — your password never leaves your device in plaintext or full hash.