This free diff checker is a quick way to compare text online. Paste two versions and it highlights every addition and removal, by line, word or character, so you can review edits, code changes and SEO files without hunting for the difference.
- How to use the diff checker
- What you can compare and how
- Seven ways SEOs use a text compare tool
- Line, word or character: choosing the right level
- Getting a clean comparison
- Reviewing a content change step by step
- FAQ
- Related tools
How to use the diff checker
- Paste the original text into the left box and the changed text into the right box.
- Choose the comparison level: line, word or character. Use line for code and config files, word for articles and character for short strings such as URLs or titles.
- Pick a view: side by side to read both versions in columns, or inline to see one merged version with changes marked.
- Tick the options you need. Ignore case treats Page and page as the same. Ignore whitespace skips differences in spaces, tabs and line endings.
- Read the highlighted result and the counts of added and removed items. Everything you paste stays in your browser, so nothing is uploaded.
What you can compare and how
Compares whole lines. It is the right choice for source code, robots.txt, redirect maps, CSV rows and any list.
Highlights changed words inside a paragraph, so an edited sentence shows only what moved or was reworded.
Marks single-letter differences. Handy for spotting a typo in a URL, a SKU or a canonical tag.
Two views of the same result. Columns suit long files; inline suits short edits.
Hide noise so you only see real changes, such as indentation or capitalization.
A quick total of what was added and what was taken out, so you can judge the size of a change at a glance.
Seven ways SEOs use a text compare tool
A diff checker is one of the most useful small tools in technical SEO, because search problems often come from a small change nobody noticed. Here is where we reach for it:
- Robots.txt versions. Compare the live file with the last known good one before a crawl drop turns into a crisis.
- Title and meta changes. Check exactly what an editor changed on a ranking page.
- Redirect maps. Compare the planned map with what a developer implemented.
- Content refreshes. See which paragraphs a rewrite touched and which stayed the same.
- Structured data. Compare two blocks of JSON-LD to find a dropped property.
- Hreflang and canonical tags. Spot a missing return link or a changed canonical in two copies of a template.
- Migration QA. Compare staging and live HTML to confirm what changed on launch day.
For structured data, tidy both versions first with the JSON Formatter so indentation does not create false differences. Then paste them in and the real changes are all that remain.
Line, word or character: choosing the right level
The level you choose controls how much detail you see. Pick the wrong one and the result is either too coarse or too noisy.
| Level | Best for | Watch out for |
|---|---|---|
| Line | Code, configs, lists, tables | One changed word flags the whole line |
| Word | Articles, emails, contracts | Slow to read on very long files |
| Character | URLs, titles, SKUs, typos | Noisy on long paragraphs |
Here is a quick example. Original: Free SEO tools for agencies. Changed: Free SEO tool for agencies. In line mode, the entire line is shown as removed and added. In word mode, only tools and tool are flagged. In character mode, just the final s is marked. Same text, three levels of detail.
Start with line mode for structured files and word mode for prose. Drop to character mode only when you know the difference is tiny and cannot see it.
Getting a clean comparison
Most confusing results come from invisible differences, not real edits. Windows and Mac files can use different line endings. Editors add trailing spaces. Copying from a web page may turn straight quotes into curly ones. If the tool shows changes that look identical, turn on ignore whitespace first. If differences remain, check the quotes and any special characters.
Compare like with like. Do not paste a full page of HTML against a rendered article; paste the same kind of content on both sides. For version history over time, a diff checker compares two snapshots only, so keep dated copies of anything you may need to roll back, such as templates and redirect files.
Privacy note: because the comparison runs in your browser, you can paste unpublished content and client files. Still, avoid pasting passwords, API keys or personal data into any tool, even one that does not upload.
Reviewing a content change step by step
When you need to compare text from a client rewrite, work in this order. Paste both versions and start in word mode with ignore whitespace on. Read the removed words first, because deleted facts, brand terms and internal links are the usual casualties. Then read the additions and check that the new claims are accurate and that the target keyword is still present where it should be.
Finally, switch to line mode to see the structure: did headings move, did a list disappear, did a paragraph merge with another? A page can keep its words and still lose its shape. Write down the changes you approve, so the next reviewer does not have to repeat the work.
Frequently asked questions
How do I compare two texts online?
Paste the original into the left box and the changed version into the right, then pick line, word or character comparison. The tool highlights what was added and removed, and shows counts. Switch between side-by-side and inline views to read the result whichever way suits you.
What is a diff checker?
A diff checker compares two pieces of text and shows the differences between them. Developers use it to review code changes, and SEOs use it to compare robots.txt files, titles, redirect maps and structured data. It highlights additions, deletions and sometimes moved text.
Can I compare text and ignore capitalization or spaces?
Yes. Turn on ignore case to treat upper and lower case letters as the same, and ignore whitespace to skip differences in spaces, tabs and line endings. These options remove noise so that only meaningful edits remain in the highlighted result.
Is the text I paste uploaded to a server?
No. The comparison happens in your browser, so both texts stay on your device. Nothing is uploaded or saved. That makes the tool suitable for unpublished drafts and internal files, though you should still avoid pasting secrets such as passwords or keys.
Why does it show differences when the two texts look the same?
Usually the cause is whitespace, line endings, curly versus straight quotes or non-breaking spaces. Turn on ignore whitespace and ignore case, then switch to character mode to find the exact character that differs. Copying from rendered web pages often introduces these hidden changes.
What is the difference between line, word and character comparison?
Line mode flags whole lines that changed, which suits code and lists. Word mode marks individual words, which suits articles. Character mode marks single letters, which suits short strings such as URLs. Choose the coarsest level that still shows the change you need.