Merge CSV Files in Your Browser: Columns Line Up by Name, Nothing Is Uploaded

CSV merger that lines up mismatched columns by header, browser-only

This free browser-based tool merges multiple CSV files into one, aligning columns by header name so mismatched columns become blank cells instead of shifting data. It runs entirely on your device—no uploads, even works offline. Supports files up to 20MB, handles quoted fields with commas and line breaks, and offers an optional source column. Perfect for combining spreadsheets with different column orders.