Text Diff Compare

What Text Diff Compare helps you do

Compare two text versions with a Split or Unified viewer. Live Myers alignment highlights removals in red and additions in green, with dual line numbers, synced scroll in Split view, and word-level token marks inside changed lines. It is built for config exports, copy edits and API responses where a changed character matters.

Diffing runs entirely in your browser. Neither side of the comparison is uploaded.

How it works

The lines of both sides are aligned with the Myers difference algorithm. Equal lines are left unmarked, removed lines are shown on the left, and added lines on the right. Within a changed line, a token-level pass marks the words that actually changed, which is why a one-word edit does not make the whole line look different.

How to use Text Diff Compare

1. Paste original text on the left and revised text on the right — the comparison updates as you type.
2. Use Split (side-by-side) or Unified view, optionally hide unchanged lines.
3. Inspect the word-level marks and the line numbers.
4. Copy a patch or either side of the comparison.

When to use it

• See what changed between two config exports before deploying.
• Review copy edits from a collaborator without track changes.
• Compare API response samples when debugging field-level differences.
• Check that a find-and-replace changed only the intended lines.
• Review a translation against the source text.
• Compare two versions of a README or a policy.

When not to use it

• Do not compare binary files or images; the diff works on text.
• Do not paste a file larger than the character or line cap; split it first.
• Do not use it as a merge tool; it shows differences but does not resolve them.

Example

Two JSON config exports differ by one timeout value and a reordered brace. The line diff flags the timeout line, and the word-level mark shows that only 30 became 60. The copied patch is attached to the change request so the reviewer sees exactly what will ship.

What you can do with Text Diff Compare

• Compare two pasted texts as you type.
• Switch between Split and Unified views.
• Highlight word-level changes inside a modified line.
• Show dual line numbers and sync scrolling in Split view.
• Hide unchanged lines to focus on the differences.
• Copy a unified patch or either side of the comparison.

Example: review a config change

Paste the old config on the left and the new config on the right. The diff updates live, so you can move the two versions into place and read the changed lines immediately.

Switch to Unified if you need one continuous view, or hide unchanged lines when the file is mostly identical. The word-level marks show whether a value or only its formatting changed.

Copy the unified patch into a ticket or review comment, or copy one side if you need to restore the original.

What to know before you start

• Each side is capped for responsiveness; split very large files before comparing.
• On narrow screens the viewer switches to Unified automatically for readability.
• The diff works on text, not binary files or images.
• It shows differences but does not merge or apply them.
• Word-level marks are a reading aid, not a semantic or security check.

Common mistakes

• Comparing files that use different line endings without realizing the diff normalizes them.
• Pasting a truncated log and assuming the missing part is unchanged.
• Reading the Split view without noticing that the two sides scroll together.
• Treating a word-level mark as a complete semantic check.
• Copying a patch that includes context lines the reviewer did not expect.
• Assuming a hidden unchanged line cannot contain a change in surrounding lines.

Troubleshooting

If the whole file appears changed, check for a line-ending or indentation difference; the comparison normalizes CRLF and LF but not tabs versus spaces.

If the tool warns about size, split the file into sections and compare them one at a time.

If the word marks look noisy, the change may be a formatting-only edit that altered whitespace across the line.

If the Split view is hard to read on a phone, switch to Unified; the viewer may do that automatically on narrow screens.

If a side is empty, the comparison treats the whole other side as added or removed.

If the diff seems to ignore a change, check whether only whitespace differs; the line and word comparison may collapse it visually.

If the same text is pasted into both sides, the tool simply shows no differences rather than warning.

Related standards and documentation

• The Myers difference algorithm is the basis for the line alignment.
• The unified patch format follows the common diff/patch convention.