Whether you are a developer looking for a missing semicolon in a configuration file, or an editor comparing two versions of a legal contract, finding differences manually is a waste of time. This is where diff tools come in.
How Diff Algorithms Work
Most modern text diff tools use an algorithm called the Longest Common Subsequence (LCS) problem, first implemented widely by the Unix diff utility in the 1970s.
The algorithm works by finding the longest sequence of characters (or words, or lines) that appear in the exact same order in both the original and the modified text. Everything that is not part of that sequence is categorized as an insertion or a deletion.
Line Diff vs Word Diff
Depending on what you are comparing, you'll want to use different granularities:
- Line Diff: Best for source code (like Python, HTML, or JSON). Code is naturally structured line-by-line, and seeing exactly which line was added or removed makes it easy to spot logical changes.
- Word/Character Diff: Best for prose, essays, and legal documents. If you only change one word in a paragraph, a line diff will highlight the entire paragraph. A word diff will highlight just the specific word that changed.
Compare Text Securely
When comparing sensitive API keys, server configurations, or private documents, you should never paste them into a tool that uploads data to a server. Our Text Diff tool runs 100% locally in your browser.
JSON Comparison
While standard text diffing is great for generic strings, it breaks down if the data is structurally identical but ordered differently. For example, in JSON, the order of keys in an object doesn't matter.
If you need to compare JSON, you should use a dedicated JSON Compare tool that parses the objects structurally and sorts them before performing the diff.