Text Diff Viewer - Compare Two Texts Side by Side

What is a text diff?

A diff (short for difference) is a comparison between two versions of a text that shows exactly what changed: which lines were added, removed, or modified. Diffs are fundamental to software development: every time you run git diff or review a pull request, you are reading a diff.

This tool performs the comparison entirely in your browser. Nothing is sent to a server. You can paste confidential configuration files, private source code, or sensitive documents without worry.

How to read a diff

There are two common display formats:

• Side-by-side: the original text appears on the left, the modified text on the right. Removed lines are highlighted red on the left; added lines are highlighted green on the right. Lines that exist on both sides but changed are shown in both panels with word- or character-level inline highlighting to pinpoint the exact change.
• Unified: both texts are merged into a single column. Lines prefixed with - were removed; lines prefixed with + were added; unprefixed lines are context (unchanged). Unified diffs are the standard format used by Git, email patches, and code review tools.

Line vs word vs character diff

This tool always performs a line-level diff first: it identifies which lines changed. For lines that were partially changed (not entirely replaced), it then performs a secondary inline diff to highlight the specific words or characters that changed within that line:

• Word diff: splits each line on whitespace and highlights changed words. Best for prose, configuration values, and most code.
• Char diff: highlights individual changed characters. Best for spotting single-character typos or small symbol changes.

Ignore options explained

• Ignore whitespace: normalises all runs of whitespace (spaces and tabs) to a single space before comparing. Lines that differ only in indentation or spacing are treated as equal. Useful for comparing reformatted code.
• Ignore case: converts both sides to lowercase before comparing. Lines that are identical except for capitalisation are treated as equal.
• Ignore empty lines: strips blank lines from both sides before diffing. Handy when one version has extra blank lines inserted by an editor.
• Ignore trailing spaces: trims whitespace from the end of each line before comparing. Prevents spurious differences caused by editors that add or remove trailing spaces.

Exporting as a patch file

Click Copy patch to copy the diff in standard unified patch format. You can paste this into a .patch file and apply it to the original file:

patch -p1 < changes.patch

Or apply it with Git:

git apply changes.patch

The patch format is compatible with GNU patch, Git, and most other diff/patch tools.

Understanding Git merge conflict format

When Git cannot automatically merge two branches, it inserts conflict markers directly into the file. Understanding this format helps you resolve conflicts manually:

<<<<<<< HEAD
content from the current branch (your changes)
=======
content from the incoming branch (their changes)
>>>>>>> feature-branch

The section between <<<<<<< HEAD and ======= is what your branch currently has. The section between ======= and >>>>>>> is what the branch being merged in has. Resolving the conflict means choosing one version, combining them, or writing a third option - then deleting all the conflict markers.

Common use cases beyond code

• Contract revisions: compare two versions of a legal document to verify only the intended changes were made.
• Configuration files: check whether two environment configs are identical or spot unexpected differences.
• Translated text: compare source and target language texts side by side to verify completeness.
• Policy documents: track changes between published versions of privacy policies, terms of service, or regulatory filings.