Text Diff

Key takeaways

• LCS line diff — the same algorithm family git uses
• Unified-style output: -, +, and context lines with a summary count
• Whitespace-sensitive: trailing spaces and tabs register as changes
• Both sides stay in your browser — useful for contracts and configs

What is a text diff?

A text diff is a line-by-line comparison of two versions of a text, showing which lines were added, removed, or left unchanged.

This tool computes a longest-common-subsequence (LCS) diff over lines — the same family of algorithm used by git. Output uses unified-style markers: “- ” for lines only in the original, “+ ” for lines only in the changed version, and two spaces for context. Comparison is whitespace-sensitive, because trailing spaces and tab changes are real changes in configs and code.

Features

• LCS line algorithm

  Minimal add/remove sets via longest common subsequence, like git's default diff.

• Unified-style output

  Familiar -, +, and context markers with an added/removed summary.

• Whitespace-sensitive

  Trailing spaces and tab changes surface as changes — critical for configs.

• Private comparison

  Both sides are processed locally and never uploaded.

How it works

1. 1

   Paste the original

   The left pane holds the before version.

2. 2

   Paste the changed version

   The right pane holds the after version.

3. 3

   Read the diff

   Removed lines show “-”, added show “+”, context stays plain.

Example walkthroughs

• Config change

  One changed line appears as “- port: 8080” and “+ port: 3000”; the rest is context.

  port: 8080
  host: localhost
  debug: false

• Added lines

  The new line shows as “+ step three” with zero removals.

  step one
  step two

Use cases

• Review config edits

  Confirm a deployment change touched only the keys you intended before shipping.

• Compare document versions

  Find edits between two exported versions when change tracking was not on.

Code snippets

• Quick line diff in the shell

  bash

  The same unified format this tool prints, from standard CLI tools.

  diff --unified before.txt after.txt
  # or with git, no repo required:
  git diff --no-index before.txt after.txt

Common errors

• Every line shows as changed

  Cause: Line endings differ (CRLF vs LF) or indentation was reformatted.

  Fix: Normalize line endings or run your formatter on both versions first.

• A tiny edit shows the whole line replaced

  Cause: Line diffs mark the full line — there is no character-level highlight.

  Fix: Read the -/+ pair together to spot the in-line change.

About Text Diff

Text Diff is a private compare workspace for two versions of anything line-based: config files, SQL, contracts, meeting notes, environment files, or generated output before and after a change. Paste the original on the left and the changed version on the right — the diff renders with removed lines marked “-”, added lines marked “+”, and a summary of how many lines changed.

Searches for “text compare” and “diff checker” usually mean one of two jobs: verifying that a config change touched only the intended lines, or finding what a collaborator edited in a document with tracking off. A line-oriented diff answers both faster than reading side by side.

The comparison is deliberately whitespace-sensitive. In YAML, .env files, and Makefiles, an invisible trailing space or a tab-for-spaces swap is a real change that can break parsing — a diff that “helpfully” ignores whitespace hides exactly the bug you are hunting. If noise from formatting bothers you, normalize with Case Converter or your formatter first, then diff.

Both inputs stay on your device. Diffing is a moment when sensitive material — credentials in configs, unreleased contract terms — is most likely to be pasted somewhere, so the client-side privacy model matters here more than almost anywhere else on the site.

Best practice: diff at the smallest meaningful scope (one file or section at a time), and remember the limit of a line diff — a one-character edit shows as the whole line removed and re-added.

Frequently asked questions

Explore more

• All tools

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• Privacy

  How client-side tools handle your data.