Data Utility
CSV Merger
Merge multiple CSV & XLSB files in your browser. Validates headers, detects row mismatches, and exports a single clean file - zero uploads, zero server.
Zero uploads
Instant processing
Free forever
Header validation
Upload Files
0 files
Drop files here or click to browse
Supports CSV & XLSB · Max 5 MB per file · Up to 1000 files
How it works
Four steps, zero setup
Everything runs in your browser. No accounts, no waiting, no privacy risk.
01
Upload Files
Drag & drop or click to select any number of CSV or XLSB files.
02
Validate
Headers, row lengths, encoding, and file integrity are checked automatically.
03
Merge
Valid files are concatenated in memory. Progress is tracked in real time.
04
Download
One click to download the merged CSV to your device. Nothing is stored.
100% Private - Your data never leaves your device
All merging and validation runs client-side in JavaScript. No data is uploaded, logged, or transmitted to any server. Safe for PII, secrets, and sensitive production data.
Zero transmission
FAQ
Common questions
Is the CSV Merger really free?
Yes. No sign-up, no paywall, no usage limits. All features available to all users, always.
Does it upload my files to a server?
No. Everything runs in your browser's JavaScript engine. Your files never leave your device. Safe for production secrets, customer PII, and sensitive payloads.
What happens when headers don't match?
Files with mismatched headers are flagged as invalid in the validation log and skipped during the merge. Only files whose headers match the first valid file are included.
What are the limits?
Maximum 1,000 files per session, 5 MB per file. These limits exist to protect browser memory - not because of server costs. Very large merges are best done in batches.
Can I merge XLSB files?
XLSB files are accepted and treated as tabular data. The first row is used as the header. Mixed CSV+XLSB merges work as long as all headers match.