CSV Merger

Upload several CSVs and merge them locally with header mapping.

Privacy-first — format, validate and inspect data entirely in your browser. Nothing is uploaded to FreeConverter.

Paste data

Tip: drag & drop a supported file onto this area.

Upload Files

Tool Options

Same Headers Only Auto Header Mapping Ignore Duplicate Rows Sort by first column

Upload multiple files with “Upload Files”, or paste CSVs separated by lines starting with --- filename ---.

Results

Results will appear here…

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How It Works

Inspector + formatter workflows for developers and QA.

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Paste or upload

Paste data or drop XML, YAML, JSON, CSV, SQL or TXT. Nothing is uploaded to our servers.

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Inspect & process

Format, validate or convert in your browser with structure stats and quality warnings.

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Copy or download

Export TXT, JSON, YAML, CSV, SQL, Excel or ZIP instantly.

Your data stays on your device — format, validate and convert locally.

About CSV Merger

Merge multiple CSV files in your browser with same-headers-only or auto header mapping, duplicate ignore, sort and preview. Part of FreeConverter’s Developer Data Toolkit for XML, YAML, CSV, SQL and API payloads.

FAQs

Is my data uploaded?

No. The Developer Data Toolkit runs entirely in your browser. FreeConverter servers never receive your input.

Who is this for?

Developers, DevOps, API engineers, DBAs and QA — for formatting, validating and inspecting structured data.

Is this free?

Yes. FreeConverter.app browser developer tools are free to use.