Text Diff & Comparison Tool
Compare two text blocks, draft revisions, or code snippets side-by-side. Spot added, removed, and modified lines instantly with zero server uploads.
Why use a client-side text comparison tool
Reviewing changes between two text drafts, legal clauses, or code revisions is a common daily task. Unlike web services that send your text to third-party cloud servers for processing, this tool runs entirely in your local browser sandbox. Your proprietary drafts, confidential contracts, and personal writings stay strictly on your machine.
The Myers diff algorithm explained
Under the hood, this tool computes the Longest Common Subsequence (LCS) between the original and modified strings. This algorithm determines the shortest sequence of additions and deletions needed to transform the original text into the target version, producing clean, intuitive difference reports without spurious line mismatches.
Practical use cases for text diffing
- Content editing: Compare proofread drafts against original manuscripts to verify requested editorial changes.
- Contract review: Identify subtle wording modifications between two versions of legal terms or vendor agreements.
- Code review: Inspect configuration files, JSON payloads, or code snippets before committing changes to source control.
- Translation verification: Check updated strings against previous source files to spot missing translations.
Interpreting diff results
Lines marked with a green background and a plus symbol (+) indicate content that was added in the new version. Lines marked with a red background and a minus symbol (-) represent content that was removed from the original text. Unchanged lines provide immediate context for where modifications occurred.
Frequently asked questions
How does this text diff checker work?
It uses an implementation of the Myers Longest Common Subsequence (LCS) algorithm to find the minimal edit script between two texts, highlighting exactly which lines and words were inserted, modified, or removed.
Is my text private and safe?
Yes. All text comparison happens completely on your device using client-side JavaScript. Nothing is transmitted to any server, recorded in logs, or cached externally.
Can I compare programming code or JSON?
Yes. The diff viewer preserves exact indentation, spacing, punctuation, and line breaks, making it suitable for comparing source code, configuration files, SQL queries, and JSON documents.
What is the difference between Unified and Side-by-Side views?
Unified view stacks changes in a single continuous stream with red (-) and green (+) indicators, similar to git diff. Side-by-side view splits the original and modified texts into parallel columns for visual comparison.
Is there a file size or character limit?
Because comparison runs directly in your browser, it comfortably handles thousands of lines and tens of thousands of words without browser lag.
