Text Diff Checker

What this tool does

The Text Diff Checker compares two blocks of text and renders an inline diff that shows exactly what changed between them. Paste your original text into the left box and your revised text into the right box; the tool runs a semantic diff algorithm and displays the result immediately below, with inserted characters highlighted in green and deleted characters shown in red with a strikethrough. It also reports the raw counts of added and removed characters so you can measure the size of the revision at a glance.

Why you might need it

Version control tools like Git show diffs for code files automatically, but there is no equivalent built into most writing environments. When you revise a client email, a legal clause, a product description, or a configuration snippet and need to confirm exactly what changed, this tool fills the gap. It is especially useful when you received a document back from a collaborator and want to see what they altered before accepting it, or when you want to verify that a copy editor’s changes match what you expected.

Writers use text diffs to track how a draft evolved between sessions. Marketers use them to audit A/B copy variants. Developers paste two versions of a config file to spot a changed value without running diff in a terminal. The inline presentation — inserted and deleted text shown together in a single stream — is faster to read than a traditional two-column side-by-side view when the changes are small and scattered.

How to use it

1. Paste your original text into the Original text box on the left.
2. Paste your revised text into the Changed text box on the right.
3. The inline diff appears below both boxes instantly — no button to click.
4. Read the green sections for additions and the red strikethrough sections for deletions; plain text is unchanged.
5. Check the stat cards for the exact character counts added and removed.
6. Use Copy diff to grab a plain-text version of the diff with [+added] and [-deleted] markers for pasting into a report or email.
7. Click Load sample to see an example if you want to try the tool first.

Common pitfalls

The diff operates at the character level and then groups changes into semantic units (words and sentences), so very minor typo fixes may appear as a word replacement rather than a single-character change. That is intentional — it produces a more readable result than marking every individual letter.

If you are comparing code, whitespace differences (trailing spaces, mixed indentation, Windows versus Unix line endings) will appear as changes because the tool compares text exactly as pasted. Normalise whitespace in your editor first if you only care about semantic code changes.

The character counts reflect the raw length of inserted and deleted text, not the number of words or “edits”. A sentence rewrite where thirty characters were deleted and thirty were added will report thirty additions and thirty deletions even if the meaning barely changed.

Tips and advanced use

Use the Load sample button to see the diff visualised before you paste your own text — it gives a clear sense of how the colour coding works. For very long documents, scroll the diff output slowly and watch for colour shifts; the semantic grouping means a single paragraph change will appear as a contiguous coloured block rather than scattered marks.

If you want a shareable record of the changes, the Copy diff button exports the diff as annotated plain text using [+text] for additions and [-text] for deletions, which survives copy-paste into any plain-text environment like email or a ticket comment.

Because the entire comparison runs inside your browser, this tool is safe for confidential content. Legal text, internal draft policies, personal letters, and unpublished work can all be compared here without the risk of the content reaching a server or being retained in any log.