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Tutorial

How to Find Differences Between Two Lists

A practical guide to identifying what's different and what's the same between any two lists, using exact and local smart matching methods.

Two Ways to Find Differences

Exact Matching

Free

Compares items character-by-character. Items match only if they are identical (with optional case-insensitive comparison). Fast and deterministic.

Best for: Emails, IDs, product codes, exact strings

Local Smart Matching

Free

Uses Levenshtein distance and token-based similarity to find near-matches. Catches typos, reordered words, and similar entries that exact matching misses.

Best for: Names ("John Smith" vs "Smith, John"), addresses, keywords with typos

Understanding the Results

Only in A

Items present in List A but not found in List B.

Only in B

Items present in List B but not found in List A.

In Both (Intersection)

Items present in both List A and List B.

Union

All unique items from both lists combined.

Symmetric Difference

Items in either list but not in both (Only in A + Only in B).

Practical Example

List A (Old Subscribers)

alice@gmail.com

bob@yahoo.com

charlie@hotmail.com

david@company.com

List B (New Subscribers)

bob@yahoo.com

charlie@hotmail.com

emma@outlook.com

frank@gmail.com

Only in A (2)

alice@gmail.com, david@company.com

Unsubscribed / Churned

Only in B (2)

emma@outlook.com, frank@gmail.com

New subscribers

In Both (2)

bob@yahoo.com, charlie@hotmail.com

Retained subscribers

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