Text Compare (Diff Checker)
FREE TOOL · NO SIGN-UP
This text compare tool finds every difference between two versions of a text. Paste the original and the changed version, click Compare, and added text is highlighted in green while removed text is shown in red, with a similarity score on top. It works for writers checking edits, teams reviewing contracts and developers comparing config files or code snippets.
How Text Comparison Works
A diff checker lines up two texts and works out the smallest set of additions and removals that turns the first into the second. Everything else is marked as unchanged. This tool uses a longest-common-subsequence approach, the same basic idea behind many version control tools.
Line, word and character diffs
You can compare at two levels. Lines mode treats each line as one unit. It’s the best choice for code, config files, lists and anything structured line by line, because it shows exactly which lines were added or removed. Words mode splits the text into words and spaces, so a single changed word in a long paragraph is highlighted on its own instead of flagging the whole paragraph. That’s ideal for prose, articles and contracts.
Some diff tools also offer character-level comparison, which highlights changes inside a word. This tool doesn’t, but words mode catches the same edits and is easier to read for most writing.
Reading the highlights
The stats bar shows how many units were Added, Removed and Unchanged, plus a Similarity percentage based on the unchanged share. In lines mode, results appear as a list: lines marked + with a green background were added, lines marked - in red were removed, and unmarked lines are the same in both. In words mode, the text flows as normal, with additions highlighted in green and deletions in red strike-through. A changed word appears as a red deletion followed by a green insertion. If nothing changed, you’ll see “The texts are identical.”
How to Compare Two Texts
Step 1 – Paste original
Paste the earlier version into Original text on the left. This is the baseline the tool compares against.
Step 2 – Paste changed text
Paste the newer version into Changed text on the right. Make sure you copy the full text from both sources, so missing sections don’t show up as false deletions.
Step 3 – Choose options
Pick Compare by Lines or Words. Then choose whether to Ignore case, which treats “SEO” and “seo” as the same, and Ignore extra whitespace, which is on by default and ignores differences in spacing and indentation.
Step 4 – Review highlighted differences
Click Compare and work through the highlights from top to bottom. Use the similarity score to get a feel for how much changed overall, then check each addition and removal. Clear resets both boxes.
Comparing Contracts and Drafts
Spotting silent edits
When a document comes back from a client, partner or another department, not every change is announced. A clause gets softened, a date moves, a “will” becomes “may”. Reading both versions side by side is tiring and easy to get wrong. Paste them in, switch to words mode and every changed word is highlighted, so small but important edits can’t hide. For legal and financial documents, always confirm important changes with the original files rather than relying on any single tool.
Tracking revisions
Writers and editors can use the comparison to see exactly what an editor changed, or to check that requested fixes were made. For SEO content, it’s a quick way to compare a page before and after an update, or to see how a competitor’s page changed between two saved copies. If you work through several rounds, keep each version so you can compare any two.
Comparing Code and Config Files
Whitespace and line endings
In code, a change in indentation is often just noise, but in some languages and file formats it matters. Leave Ignore extra whitespace on to focus on real changes, and turn it off when you need to see indentation edits. Windows and Unix line endings are handled automatically, so a file saved on a different system won’t show every line as changed.
When to use git diff
For files under version control, git diff and your code host’s pull request view are the right tools. They track history, handle whole folders and work with very large files. An online comparison is better for quick checks: two snippets from a chat, a config file copied from a server, or a robots.txt before and after an edit.
Text Compare vs Plagiarism Checking
Two texts vs the web
A diff checker compares two texts that you provide. A plagiarism checker compares one text against a large database of web pages and documents to find matching passages elsewhere. If you want to know what changed between two versions, use text compare. If you want to know whether content was copied from somewhere online, you need a plagiarism tool.
Paraphrase detection limits
Text comparison is literal. If someone rewrites a sentence with different words, it shows up as removed and added text, not as “the same idea.” That’s what you want for tracking edits, but it means a low similarity score doesn’t prove two texts are unrelated.
Comparison Pitfalls
Reflowed paragraphs
If line breaks moved, for example when text was copied from a PDF, lines mode marks almost everything as changed. Switch to words mode, which isn’t affected by where lines break.
Smart quotes vs straight quotes
Word processors often convert " and ' into curly quotes. They look similar but count as different characters, so they show as changes.
Confidential text in online tools
This tool runs entirely in your browser and doesn’t upload or store your text. Even so, follow your organisation’s rules for sensitive documents.
Spot Every Change Before You Sign Off
Small edits can carry big consequences, so check them before you approve or publish. Use text compare for drafts, contracts and code, then tidy up the final version with the Duplicate Line Remover, clean spacing with the Extra Spaces Remover and check the length with the Word Counter. Find more writing and SEO utilities in the FHSEO Hub free SEO tools collection.