Change Data Capture (CDC) for CSV and Excel Files
Change data capture (CDC) answers one question: what changed since last time? For files, you can answer it by comparing two snapshots.
In databases, CDC usually means reading the transaction log and streaming every insert, update and delete as it happens. Tools such as Debezium do that. A lot of data never lives in such a database: it arrives as a daily CSV export or an Excel report. For those, the practical form of CDC is a snapshot comparison.
Keep yesterday's file and today's file. Open Data Comparison, load both, and choose the key column that identifies a row, such as id or order number. Rows whose key appears only in today's file are the inserts. Rows whose key appears only in yesterday's file are the deletes. Rows with the same key but different values are the updates, and each changed cell is shown as old to new. You can download the differences as CSV, Excel, JSON or Parquet.
The tool also tells you if columns were added or removed between the two files and if a column's type changed, which are the changes that most often break a downstream load. Use Ignore spaces, Ignore case and a number tolerance so harmless differences, such as 36 and 36.0, are not reported.
Know the limits. This is a batch comparison of two files, not a live stream, and it does not read database logs. Both files must be CSV or Excel, and the key must identify each row. If a key repeats, add a second key column. Everything runs in your browser and nothing is uploaded.
Related tool pages
- Compare Two CSV Files: Compare two CSV or Excel files by a key column and see added, removed and changed rows. Free, runs in your browser.
- Compare Two Excel Files: Compare two Excel (.xlsx) files by a key column and see every added, removed and changed row and cell. Free, and your files stay in your browser.
- CSV Diff Tool: Find the differences between two CSV files online: which rows were added, removed or changed, cell by cell. Free, in your browser.
- CDC for CSV and Excel Files (Change Data Capture): Change data capture for files: compare two CSV or Excel snapshots and list inserts, updates and deletes by key. Free, private, runs in your browser.
- Detect Changes Between Two CSV Files: Find new, deleted and edited rows between two CSV files, cell by cell, matched by a key column. Free, and your files stay in your browser.
- Find New, Updated and Deleted Rows Between Two Files: List the new, updated and deleted rows between two CSV or Excel files by key and download the differences. Free and private.
How to use the Data Comparison: step by step
- Open Data Comparison.
- Load the earlier file and the latest file.
- Choose the key column, or two columns if one repeats.
- Read the added, changed and removed rows and download the differences.
When to use the Data Comparison
- Find what changed in a daily export
- Check an incremental load before it runs
- Audit edits between two versions of a report
- Verify a migration by comparing source and copy
Example
Input: before.csv + after.csv, key = id
Output: Added 3 · Removed 2 · Changed 5
Frequently asked questions
Can I use it for change data capture (CDC)?
For files, yes. Load yesterday's snapshot and today's, choose the key, and the added rows are the inserts, the changed rows are the updates and the removed rows are the deletes. It is a snapshot comparison, not log-based CDC: it does not read database logs or stream changes live.
How do I find new, updated and deleted rows between two files?
Load both files, choose a key column such as id, and read the three lists: added (new), changed (updated, with the old and new value of each cell) and removed (deleted).
Can the files be different formats?
Yes. A can be a CSV and B an Excel file. Columns are matched by name. JSON and Parquet files are not supported here, so convert them to CSV first.
Can Data Comparison do change data capture (CDC)?
It does the snapshot version of CDC for files. Compare the earlier and the latest export by key: added rows are inserts, changed rows are updates and removed rows are deletes. It does not read database logs or run in real time.
Tip: Pick a key that is unique in both files. If one column repeats, add a second, such as id and region.