Knowledge Base
Best Practices for Normalizing Emails Before Hashing
Best Practices for Normalizing Emails Before Hashing
To achieve reliable and consistent results when hashing email addresses, normalization is crucial. Without it, slight variations in email formatting can lead to mismatched hashes, affecting tasks like identity matching and deduplication. Here are four essential practices to follow when normalizing emails for hashing:
1. Convert to Lowercase
- Why: Email addresses are generally case-insensitive, meaning variations like
User@Domain.com
anduser@domain.com
should be treated as identical. - How to Normalize: Convert the entire email address to lowercase.
- Example:
User@Domain.com
becomesuser@domain.com
.
2. Trim Whitespace
- Why: Users often add spaces at the beginning or end of their email by mistake, which can result in hashing inconsistencies.
- How to Normalize: Remove all leading and trailing whitespace from the email.
- Example:
" user@domain.com "
becomesuser@domain.com
.
3. Remove Periods in the Local Part for Gmail Addresses
- Why: Gmail ignores periods in the local part of email addresses, treating
username@gmail.com
anduser.name@gmail.com
as identical addresses. - How to Normalize: For Gmail addresses (
gmail.com
andgooglemail.com
), remove all periods from the local part of the address. - Example:
user.name@gmail.com
becomesusername@gmail.com
.
4. Handle Aliases Properly
- Why: Many providers, particularly Gmail, allow users to add “+” symbols in the local part to create unique aliases (e.g.,
user+alias@gmail.com
), which are often used to filter or categorize emails. Normalizing aliases can prevent redundant entries in hashed data. - How to Normalize: Remove everything after a
+
symbol in the local part for providers that support this feature. - Example:
user+promo@gmail.com
becomesuser@gmail.com
.
Example Data: Normalization and Hashing
Below is example data showing raw emails, their normalized version, and the resulting SHA-256 hash of each normalized email:
Original Email | Normalized Email | SHA-256 Hash |
---|---|---|
User.Name+promo@gmail.com | username@gmail.com | f7976af5cad49504523379918222f1da1c1e231cd5d0770603c3e71e5e30e030 |
admin@Example.com | admin@example.com | 258d8dc916db8cea2cafb6c3cd0cb0246efe061421dbd83ec3a350428cabda4f |
JOHNDOE@Yahoo.COM | johndoe@yahoo.com | 0be12621ac1b083b13be10c0e16d3c0de3d72005056c4cfe72d218ce824f2977 |
user.name+news@gmail.com | username@gmail.com | f7976af5cad49504523379918222f1da1c1e231cd5d0770603c3e71e5e30e030 |
alice@domain.com | alice@domain.com | 4931ae9f911d21f9ba59dda70af400c9be1a06bedaeb60ad372e336c69d70f5b |
Each normalized email is then hashed using SHA-256, resulting in a unique, consistent hash value for consistent identification across datasets. Following these steps minimizes duplicates and ensures data accuracy.