How do I compare two texts and see what changed?

Paste the first version into Original (A) and the second into Modified (B). The Diff shows added, removed and unchanged lines, with changed words highlighted inside modified lines. Use Swap to reverse the two sides.

How do I ignore spacing or capital letters when comparing?

Turn on Ignore whitespace to skip spacing differences, or Ignore case to treat upper and lower case as the same. Your original text is still displayed as you entered it.

Can I compare files instead of pasting text?

Yes, use Load a text file to load plain text such as .txt, .csv, .log or .md. Binary files are rejected, and the tool shows an error if the file cannot be read.

Why are unchanged lines hidden in the diff result?

The Context setting controls how many unchanged lines show around each change: 0, 1, 3 or 5 lines, or All. Choose All to see the full text with changes highlighted. A note counts the hidden lines.

Why does a very large comparison show changes as whole blocks?

The comparison cost grows with the product of both line counts, so above about 4 million cells the tool simplifies it. Only identical lines at the start and end are matched; everything in between shows as one removed block and one added block.

Yes. Every tool is free to use, with no account and no credit card. The work runs on your device rather than on our servers, which is what keeps it free to run.

Does it work on mobile?

Yes. It runs in current mobile browsers on iOS and Android, with nothing to install.

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Free Text Diff

Compare two blocks of text and see exactly what changed. Line-by-line diff with added, removed, and unchanged lines.

Runs in your browserNo sign-up, no pop-upsNo login requiredFree forever

Works offline once loaded

Ignore caseIgnore whitespace

Context:

Original (A)

Modified (B)

+3 added−2 removed2 unchanged

Diff

Link shares your options, not your text

+The quick brown fox leaps over the lazy dog.

−The quick brown fox jumps over the lazy dog.

Pack my box with five dozen liquor jugs.

+How amazingly quick daft zebras jump!

−How vexingly quick daft zebras jump!

The five boxing wizards jump quickly.

+Now is the time for all good men.

Common uses

Compare Code SnippetsSpot exactly what changed between two versions of a code snippet, config, or script.
Compare Document DraftsFind every change between two drafts of a document, contract, or article — line by line.
Compare Data and CSV FilesSpot differences between two versions of exported data, CSVs, logs, or configuration.
Compare Translation VersionsSee what changed between two versions of a translated document, subtitle file, or localisation string.
Track Changes in Content RevisionsCompare original and edited versions of an article, blog post, or marketing copy to review what changed.

How It Works

Text Diff uses a hand-written Longest Common Subsequence (LCS) algorithm implemented directly in this tool — no external diff library. Everything runs in the browser; your text is never sent to a server.

1
Text is split into lines
Each textarea's content is split on newline characters into an array of lines. Optional normalisation (lowercasing, collapsing whitespace) is applied to a copy of those arrays before comparison, while the originals are kept for display.
2
LCS table computed in a Uint32Array
A bottom-up dynamic-programming table is built in a typed Uint32Array — O(m×n) in both time and memory. For inputs whose combined cell count would exceed 4 million (about 16 MB), the algorithm falls back to a coarser block diff automatically so the page stays responsive.
3
Word-level highlights on changed lines
When a deleted line is immediately followed by an inserted line, a second LCS pass runs on the tokenised words of that pair (split on whitespace). This produces inline highlighted segments showing exactly which words changed within the line, not just which lines changed.
4
Unified-diff view with context collapsing
The ops list is rendered as a unified diff with +/− prefixes and colour coding. Unchanged lines outside the configurable context window (default: 3 lines) are collapsed behind an ellipsis. The full result can be copied to the clipboard or downloaded as a plain-text .txt file.

Related Tools

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CSV Diff

Compare two CSV files by a key column and see exactly which rows were added, removed, or changed — with the specific fields that differ shown old to new. Handles quoted fields; runs entirely in your browser.

Try it

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