An editor sends back a revised draft. A colleague returns a contract with "a few small changes." A translated file comes back after review. In every case, the real question is the same: what actually changed? Reading two long documents side by side to catch every edit is slow and error-prone — a dedicated comparison approach is faster and far more reliable.
What a Diff Tool Actually Does
"Diff" is short for difference. A text diff tool compares two versions of a text line by line and classifies every line as one of three things:
- Unchanged — identical in both versions
- Removed — present in the original but missing from the new version
- Added — new in the second version, not present in the original
This is the same underlying approach used by version control systems like Git to show what changed in a file, applied to plain text instead of code.
Comparing Plain Text or Copy
For blog drafts, emails, articles, or any plain text, paste the original into one box and the revised version into another using our Text Diff Checker. It highlights every added line in green and every removed line in red, with a summary count so you can see the scale of the changes at a glance — no upload, no file conversion, and nothing leaves your browser.
Comparing Word Documents
Microsoft Word has a built-in comparison feature: Review → Compare → Compare, which merges two .docx files and marks up the differences as tracked changes. This works well when both versions are already Word files. For a faster, format-agnostic comparison, copy the text out of both documents and paste them into a plain text diff tool instead.
Comparing PDFs
PDFs are a page-layout format, not plain text, so a text diff tool can't read them directly. To compare two PDFs:
- Open each PDF and select/copy the text content (or use a PDF-to-text extraction tool)
- Paste each version's text into a text diff tool
- Review the highlighted differences
This won't catch purely visual changes (font, layout, images) — only differences in the actual text content.
Getting More Accurate Results
Line-based diff tools compare whole lines. If a paragraph is written as one long line and you change a single word, the entire line shows as changed — which is technically correct but not always precise enough. For more granular results:
- Break long paragraphs into one sentence per line before comparing
- Remove unrelated formatting differences (extra spaces, inconsistent line breaks) from both versions first
- For source code specifically, use a code-focused diff tool that understands syntax, rather than a plain text comparison