JSONL Diff / Compare
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Compare
JSONL Diff / Compare
Compare two JSONL files and see exactly what changed. Match records by a key path (the right answer 95% of the time — comparing two snapshots of a dataset by id), by line position (when the files are supposed to be parallel), or by canonical-object equality. Get added / removed / changed counts plus a per-field diff for each changed record. 100% in-browser.
Match modes
Key path (semantic)
The default. Pair records from A and B by the value at a chosen path (e.g. id).
Records in A whose key has no match in B are reported as removed; records
in B whose key has no match in A are added; pairs where the rest of the
record differs are changed, with a per-field diff.
Line position
Pair record N from A with record N from B. Use this when both files are expected to be the same length and in the same order — e.g. comparing the output of two pipeline runs.
Canonical object
Sort keys recursively and compare whole records. A record in A is "still present" in B if some record in B has the exact same canonical form, regardless of where it sits. Tells you what set of records changed, not which ones; faster than per-field diff on big files.
Per-field diff
For changed records, the diff lists each field that differs:
id=42 (changed):
- age: 30
+ age: 31
- city: "Berlin"
+ city: "Munich"
+ email: "[email protected]" (added)
- phone: "..." (removed)Tips & common pitfalls
- Key path mode needs unique keys. If multiple records in A share the same key value, only the first is paired. Dedupe first or pick a more specific path.
- Float comparison is exact.
0.1 + 0.2≠0.3; if you need tolerant comparison, round both files first. - Order of fields doesn't matter in semantic / canonical modes. It does matter in raw text diff; use a text diff tool for that.