free_tool
Diff Checker Text & JSON
Paste two versions and see exactly what changed: every line added, removed or left alone, with line numbers. JSON mode pretty-prints both sides first, so reordered whitespace and minified payloads stop reading as noise and you get the real structural diff. It runs in your browser.
- 1-host = localhost
- 1+host = db.internal
- 22 port = 5432
- 3-timeout = 30
- 3+timeout = 10
- 44 retries = 3
- 5+pool_size = 20
A diff catches the change you made. It won't tell you the change was safe. I review the risky ones, config edits, schema migrations, API payload shifts, before they reach production.
Pressure-test a risky change: book a callLine-level diff using a longest-common-subsequence pass, so an inserted line in the middle shifts nothing below it. Nothing leaves the page; the comparison happens entirely client-side.
see_what_actually_changed
The change you made, not the formatting around it
Eyeballing two blobs of text is how a flipped boolean or a dropped field slips through review. A line diff puts the additions and deletions in front of you, with line numbers, so there's no guessing which version has what.
JSON is the worse offender: one side minified, the other pretty-printed, and suddenly every line looks different. JSON mode parses and re-prints both sides the same way before diffing, so you only see the values that genuinely changed. If either side isn't valid JSON, it tells you and falls back to a plain text compare.
faq
Questions & answers
- How do I compare two text files online?
- Paste the original text in one side and the changed text in the other, and the tool runs a line-level diff and shows additions and deletions with line numbers, plus a summary count. It works on anything you can paste as text: logs, config, prose, or source code.
- How does the diff algorithm work?
- It uses a line-level LCS (longest common subsequence) diff, so it finds the longest run of unchanged lines and marks the rest as added or removed. This keeps related changes lined up rather than reporting every line after an insertion as different.
- What does JSON mode do differently?
- JSON mode pretty-prints both sides before diffing, so formatting noise like indentation and whitespace is normalized away and you see the real content change. Be aware it does not reorder object keys, so two objects with the same keys in a different order will still show as different unless they already match. It ignores formatting differences, not key order.
- Can it handle large files?
- It is built for pasting two blocks of text and comparing them in the browser, so it handles typical files and snippets well, but a very large diff is bounded by your browser's memory and will get slow. For multi-megabyte files a local diff tool is a better fit.
- Is anything I paste uploaded?
- No. Both sides are compared entirely in your browser and nothing is sent to a server or stored, so it is safe to diff internal config, logs, or private code.
A change that has to be right the first time?
Config edits, schema migrations, API payload shifts: the diffs where a wrong line costs you. I'll review the risky ones before they ship. Book a call, or leave your email.
Prefer proof first? See how this plays out in real case studies →