Diff and Comparison Tools
Diff Tools answer two questions: what changed, and what is missing. Use them to compare two versions of a config file, a deploy manifest, an API response or a contract draft, or to check two exports, mailing lists or inventories against each other. Developers, QA engineers, ops staff and analysts reach for them when a git checkout or a spreadsheet formula is more effort than the question deserves.
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All Diff Tools (2)
Which tool do I need?
See what changed between two versions of a config file
Paste or upload both versions into the Online Diff Tool. It shows git-style hunks of added and removed lines, with options to ignore whitespace and case.
Find customers in last month's export who are missing from this month's
Paste each export as one item per line into List Comparison and read the Only in A group. Copy it out or download the report.
Check whether two lists hold the same items in a different order
List Comparison ignores order and counts duplicates once, so a 100% similarity means the same distinct items in both lists.
Review edits to a long document before approving them
Put one sentence per line in both versions, then diff them. Line-based diffs of prose are much easier to read that way.
About Diff Tools
The two tools treat input differently, and picking the right one avoids confusing results. The Online Diff Tool cares about order: it runs the Myers algorithm, the same family git diff uses, and shows added and removed lines in unified-diff hunks with up to three lines of context. List Comparison ignores order and repeats: it treats each list as a set and shows items in both, items only in List A and items only in List B, with a similarity percentage. Two lists that are only sorted differently produce many changes in the diff tool and none in the list comparison.
Both compare whole lines. The diff tool has no word-level highlighting and does not detect moved blocks, so normalise input first: beautify minified JSON with the JSON Formatter, put prose one sentence per line, and strip timestamps from logs. Turn on Ignore whitespace when Windows CRLF line endings make every line look changed. List Comparison is case-insensitive by default and trims whitespace; switch case sensitivity on for IDs and file paths. Files you load into the diff tool are read with FileReader and stay on your machine.
Guides
- How Text Diff Works: Reading Changes Like a Code ReviewerFrom the Myers algorithm to unified diff hunks, learn how diff tools decide what changed and how to compare configs, logs and documents without noise.
- Cleaning Up Text Lists: Spaces, Blank Lines, Duplicates and CommasPasted lists are never clean. The order of operations that fixes them, why duplicates survive deduplication, and how to reshape a column into a comma list and back.
Frequently asked questions
When should I use a set comparison instead of a line diff?
Use a set comparison when the inputs are collections and order carries no meaning, such as lists of emails, SKUs, package names or user IDs. Use a line diff when order matters, such as code, configs, logs and documents, where a moved or inserted line is a real change you need to see.
Why does a diff mark a whole line as changed when I edited one word?
Line-based diffs, including git diff by default, treat a line as the smallest unit. An edited line is reported as the old line removed and the new line added. Splitting text into shorter lines, one sentence or one JSON key per line, keeps each reported change small.
How do I compare two JSON files that are formatted differently?
Format both with the same tool first. Beautify each file in the JSON Formatter so every key sits on its own line, then diff the results. Keys that appear in a different order will still show as removed and added lines, because a line diff sees order.
Can I compare more than two files or lists at once?
No. Both tools compare exactly two inputs. For three or more versions, compare them in pairs, for example each list against a reference list, and combine the Only in A or Only in B results.
Do the comparison tools keep a copy of what I paste?
No. Both tools run in your browser. Text and uploaded files are compared locally, and the List Comparison report is generated and downloaded on your machine.