Email Hasher
A privacy-preserving tool for advocacy organizations that need to swap supporter lists without exposing raw email addresses to each other.
Verified Your emails never leave your browser. This page works offline. How do I verify? →
This page makes zero network requests after it loads. You can confirm that yourself:
- Open your browser's DevTools (
⌘ / Ctrl + Shift + I), click the Network tab, reload the page, then hash a file. The list should stay empty. - Or put your computer in airplane mode and run the tool — everything still works.
- Or download the release bundle and open
index.htmlfrom a folder on your computer.
01Upload
Drop a CSV here, or click to choose a file
02Recipe
Both orgs must use the exact same passphrase. Share it out-of-band — in person, by phone, or Signal. Never over email.
03Run
Upload the hashed versions of both lists — the files you downloaded from the Hash tab. Compare works on hashes only; it will refuse to run on raw email CSVs.
01Upload both hashed lists
Drop List A
Drop List B
02Choose output
03Run