How large of a diff can I run here?

Best for small or medium texts (hundreds of KB). Very large inputs may slow down because everything runs in your browser.

How do I reset and start over?

Use the Clear buttons above each text area to wipe the inputs, or Swap to flip sides before comparing again.

RunTools.dev

Diff

Diff Viewer

Compare two texts with unified or split view, full or incremental context.

Diff Viewer

Compare two texts with unified or split view, full or incremental context.

Left (original)

Right (changed)

View mode

Context

+0 additions-0 deletionsShowing Full diff

Unified diff

Single column with + / - markers.

What

Diff Viewer definition

A diff viewer highlights additions and deletions between two texts.

Cases

Use Cases

Review changes between versions

Generate a patch-style diff

Verify edits before publishing

How To

How to Compare Two Texts

A step-by-step guide to visualizing differences between original and changed text.

Paste texts

Paste the original on the left and the updated version on the right.

Select view mode

Choose unified or split view, and full or incremental context.

Review changes

See highlighted additions and deletions, then copy the diff.

Knowledge

Understanding Diff and Version Control

What is a Diff?

A diff (difference) shows changes between two versions of text. It identifies added, deleted, and modified lines. Diffs are fundamental to version control systems and code review processes.

Diff Algorithms

The most common algorithm is LCS (Longest Common Subsequence). It finds the longest sequence of lines that appear in both versions, then shows differences around those common lines. Myers' algorithm is a popular efficient implementation.

Unified vs Split View

Unified diff shows changes in a single column with + for additions and - for deletions. Split (side-by-side) view shows original and modified versions in parallel columns. Each format has advantages for different review styles.

Context in Diffs

Context lines are unchanged lines surrounding modifications. They help reviewers understand where changes occur. Standard diff shows 3 lines of context by default. More context aids understanding; less context focuses on changes.

Diff in Version Control

Git, SVN, and other version control systems use diff internally to store changes efficiently. Patch files are structured diffs that can be applied to recreate changes. Understanding diffs is essential for code review.

FAQ