
Hem and Haw by Tin Le
Looks for hashed email addresses (HEMs) and other personal information sent to third parties.
1 User1 User
You'll need Firefox to use this extension
Extension Metadata
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About this extension
https://tincangit.github.io/hemandhaw-study/
About Hem and Haw:
This browser extension monitors when hashes of your personally identifiable information (like emails or phone numbers) are sent to third parties.
How it works:
1. You enter email addresses, phone numbers, and/or other details, and press submit.
2. Hem and Haw creates hashes of these inputs.
3. When a matching hash is detected being sent to a third party, Hem and Haw takes note and logs to our server:
- Type of data (e.g., email),
- Hash type (e.g., MD5),
- Third party's hostname,
- Originating website's hostname,
- Where in the transmission (HTTP request) the hash was found,
- HTTP Referer,
- User Agent,
- Whether you use an adblock and your self-reported privacy-consciousness score
At any point, you can stop Hem and Haw from searching for hashes, add/modify/delete the PII to search for, and see the logs of transmissions. You can use Hem and Haw to see where your hashed PII is being sent from and to!
What Hem and Haw does NOT collect:
- Your actual personal data (e.g., email addresses or phone numbers),
- HTTP request details and data,
- Any other personal information. Your IP address is also not collected by our server.
IMPORTANT NOTE:
Hem and Haw will clear all results when you clear all history.
Data collection is approved as part of a University of Calgary research study: REB25-0355_MOD1.
About Hem and Haw:
This browser extension monitors when hashes of your personally identifiable information (like emails or phone numbers) are sent to third parties.
How it works:
1. You enter email addresses, phone numbers, and/or other details, and press submit.
2. Hem and Haw creates hashes of these inputs.
3. When a matching hash is detected being sent to a third party, Hem and Haw takes note and logs to our server:
- Type of data (e.g., email),
- Hash type (e.g., MD5),
- Third party's hostname,
- Originating website's hostname,
- Where in the transmission (HTTP request) the hash was found,
- HTTP Referer,
- User Agent,
- Whether you use an adblock and your self-reported privacy-consciousness score
At any point, you can stop Hem and Haw from searching for hashes, add/modify/delete the PII to search for, and see the logs of transmissions. You can use Hem and Haw to see where your hashed PII is being sent from and to!
What Hem and Haw does NOT collect:
- Your actual personal data (e.g., email addresses or phone numbers),
- HTTP request details and data,
- Any other personal information. Your IP address is also not collected by our server.
IMPORTANT NOTE:
Hem and Haw will clear all results when you clear all history.
Data collection is approved as part of a University of Calgary research study: REB25-0355_MOD1.
Rated 0 by 0 reviewers
Permissions and dataLearn more
Required permissions:
- Download files and read and modify the browser’s download history
- Access browsing history
- Access browser tabs
- Access browser activity during navigation
Optional permissions:
- Access your data for all websites
More information
- Add-on Links
- Version
- 3.6.0
- Size
- 1.44 MB
- Last updated
- an hour ago (Sep 19, 2025)
- Related Categories
- License
- MIT License
- Privacy Policy
- Read the privacy policy for this add-on
- Version History
- Tags
- Add to collection
Release notes for 3.6.0
- Added clear extension data button
- Updated interface, now has a separate welcome page and survey page
- Now reports referer of hashed transmissions
- New survey item: Have you ever been notified your data has been in a data breach?
- Bug fixes
For prolific users:
- Hem and Haw now reports to us the number (up to 10) of unique domains you visit between daily Prolific heartbeat pings. This is to help determine sufficient usage for weekly bonus payments. If you visit 10 or more unique domains, it will only report 10+, not the exact number.
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