Text Diff Checker
Compare two texts and highlight every added or removed word. Runs in your browser.
About this text diff checker
This text diff tool compares two versions of a text and highlights what changed, line by line and word by word. It is for anyone who needs to know what changed between two drafts, two config files or two copies of a contract.
Paste the original on the left and the new version on the right. Removed lines turn red and added lines turn green. Inside an edited line, the exact words that changed get a darker highlight, so a date that went from 3 March to 10 March stands out at once. You can read the result side by side, as an inline list, or as a redline of the whole text.
Your text never leaves your browser. There is no upload, no saved copy and no share link. That matters when the file holds passwords, customer data or a draft nobody should see yet.
Features
Three views
Side by side shows both versions in aligned columns with line numbers. Inline lists removed lines with a minus and added lines with a plus, like a code review. Redline shows the full text once, with removed words struck out.
Lines, words or characters
Words mode is the default. Characters mode goes down to single letters and counts an emoji with a skin tone, or a joined Bengali or Hindi letter, as one character.
Smart line matching
Edited lines are paired with their closest new version by similarity, not just by position. One inserted line doesn't push every line after it out of line.
Ignore case and whitespace
Treat "Hello" and "hello" as equal, or skip changes in indentation and extra spaces. You still see your original text, exactly as typed.
Jump between changes
Press Alt + Down arrow or Next to go to the next change. The counter shows where you are, for example Change 3 of 12, and wraps around at the end.
Hide unchanged lines
Only changes collapses long runs of identical lines and keeps 3 lines of context around each change. Click a collapsed bar to open it.
Patch export
Copy or download the changes as a standard unified diff (.diff) with 3 lines of context.
How to use the text diff checker
- 1Paste the original text on the left and the changed text on the right, or open two files.
- 2Pick Side by side, Inline or Redline, compare by lines, words or characters, and set the ignore options.
- 3Jump through the changes with Next or Alt+Down, then copy or download the patch.
When to use it
Checking a returned document
Someone edited your draft but didn't track changes. Paste both versions and every changed word shows up. Use Redline view for this.
Finding the setting that broke something
Compare a working config with a broken one. Turn on Ignore whitespace so reindented lines don't bury the one value that matters. For JSON, format both files with sorted keys first so key order isn't counted as a change.
Comparing two lists
Exported two lists of emails or SKUs? Sort both lists and remove duplicate lines first, then compare. Each missing or extra item appears as one added or removed line.
Catching tiny edits
Characters mode catches a swapped digit in an invoice number, a missing accent or a comma that moved.
How does a text diff work?
A diff tool finds the longest run of lines that both texts share, in order. Anything outside that shared run was either removed from the original or added in the new version. This tool uses the Myers diff algorithm, published by Eugene Myers in 1986. Git uses it by default too. It finds the smallest set of removals and additions that turns one text into the other.
Then each block of changed lines gets a second pass. Similar lines are paired and compared word by word, so you see that one word changed rather than a whole line being swapped. Lines with no close match stay plain removals or additions.
Which view should I use: side by side, inline or redline?
It depends on what you are comparing.
- Side by side: code, configs and data, where line numbers matter.
- Inline: phones and narrow windows. It also reads like a code review.
- Redline: prose. It marks changed words in place. If a paragraph was rewrapped onto different lines, turn on Ignore whitespace and only the real word changes stay marked.
What do Ignore case and Ignore whitespace change?
Ignore case compares letters without regard to capitals. Ignore whitespace treats any run of spaces or tabs as one space and skips spaces at the start and end of a line. Both only change how lines are matched. The text on screen is always your original.
Line endings are normalized for you. A file saved on Windows (CRLF) and the same file saved on a Mac (LF) compare as identical, and a missing newline at the end of the file isn't flagged.
What is a unified diff?
It is the plain text patch format from GNU diff, also used by Git. Lines starting with - were removed, lines starting with + were added, and lines starting with a space are context. A header such as @@ -3,7 +3,8 @@ means the change covers 7 lines from line 3 of the old file and 8 lines from line 3 of the new one. The patch command can apply the file to the original to rebuild the new version.
Why use Mavros
| Mavros | Typical upload sites | |
|---|---|---|
| Where your text goes | Stays in your browser | Uploaded to a server, sometimes saved |
| Ignore case and whitespace | Free | Often a paid feature |
| Next and previous change | Buttons and keyboard shortcuts | Often missing or paid |
| Hide unchanged lines | Built in, expandable | Often a paid feature |
| Redline view for prose | Included | Usually line view only |
| Unified diff export | Copy or download .diff | Sometimes |
Tips
- Press Alt + Down arrow right after pasting to jump to the first change.
- Pasted the versions the wrong way round? Use Swap, so removals and additions read correctly.
- Drop a file onto either box instead of copying its contents.
- If the similarity is very low, check you pasted the right files. Two unrelated texts can't produce a useful diff.
- Need to make the same fix across the whole text after you spot it? Use Find and Replace Text, then compare again.
Questions
How do I compare two texts for differences?
Paste one version in each box. Differences are highlighted right away, red for removed and green for added. Inside edited lines, the changed words get a darker color.
Is my text uploaded anywhere?
No. The comparison runs in your browser, and nothing is sent or saved. You can even disconnect from the internet after the page loads and it keeps working.
Can I ignore whitespace or capital letters?
Yes. Turn on Ignore whitespace to skip indentation and extra spaces, and Ignore case to treat upper and lower case as equal. The displayed text stays exactly as you pasted it.
Should I compare by words or by characters?
Use words for most text and characters for typos. Words mode marks whole words that changed. Characters mode marks single letters, digits and punctuation. Lines mode marks only whole lines.
Can I compare two files?
Yes. Use Open file under each box, or drop a file onto it. Any plain text file up to 20 MB works, including .txt, .csv, .md, .json and source code.
Can it compare Word or PDF documents?
Not directly. Copy the text out of each document and paste it in. The comparison then works on the plain text, which is usually what you want to check anyway. If you need totals as well, run each version through the Word Counter.
What does the similarity percentage mean?
It is the share of lines that are unchanged across both texts. 100% means every line matches. 50% means half the lines differ or are new.
How large a text can it compare?
Up to 200,000 characters in total updates as you type. Larger texts compare when you press Compare or Ctrl + Enter. Two huge texts that are almost entirely different stop after a few seconds with a message.