When you have two versions of something and you need to know what changed, reading line by line is slow.
A diff checker does it for you.
Start here:
- Open the Text Diff Tool.
- Paste the original on the left.
- Paste the modified version on the right.
Quick start: get a clean diff
- Open the Text Diff Tool.
- Paste both versions.
- Choose an output format:
- Unified diff when you want a single list of changes
- Side-by-side when you want to review context
- If you are only looking for meaning changes, turn on:
- Ignore whitespace (useful for formatting changes)
- Ignore case (useful for titles and labels)
How to read diff output
Most diff formats use simple markers:
- Lines starting with
-were removed - Lines starting with
+were added - Lines with no prefix are unchanged context
If you are reviewing a change request, focus on the + and - lines first.
Examples
Example 1 (beginner): compare two versions of a paragraph
Use this when you are editing copy, policy text, or a message you want to send.
- Ignore whitespace if you are only reflowing lines.
- Keep whitespace on if formatting matters (poetry, code blocks).
Example 2 (professional): review a config change
Config files often break because of one line:
- a missing comma
- an extra quote
- a moved bracket
If the file is JSON, format both versions with the JSON formatter first so you are comparing clean structure instead of random whitespace.
Example 3 (professional): compare two API responses
If you have two JSON payloads and a bug only happens "sometimes":
- Format both payloads.
- Diff them.
- Look for the first field that differs.
Common mistakes (and the fix)
| Mistake | What you see | Fix |
|---|---|---|
| Comparing wrapped lines | lots of noise from line breaks | normalize first; try Remove line breaks |
| Ignoring whitespace when you should not | changes disappear | turn off ignore whitespace for code |
| Pasting tabs and spaces inconsistently | false differences | normalize indentation first |
Troubleshooting
"The diff is all red and green"
That usually means the text shifted lines.
Causes:
- added or removed line breaks
- copy/paste from a PDF or chat app that changes wrapping
Fix:
- Normalize line breaks first.
- Or switch to side-by-side to keep context.
"My JSON diff is unreadable"
Format both sides first. Then diff.
Use:
If you only do 3 things
- Pick side-by-side when you need context.
- Ignore whitespace for formatting-only changes.
- Format JSON before you diff it.
Related tools
- Format and validate JSON with the JSON formatter.
- Normalize wrapping with Remove line breaks.
Privacy and security
Textavia's diff tool runs locally in your browser. Your text is not uploaded to a server.