Back to Merge CSV
    Common Problem

    "File Too Large to Upload"

    You need to merge CSV files, but every online tool says your files are too large. 50MB limit. 100MB limit. Upload stuck at 99%. Timeout errors.

    The Upload Trap

    Here's the pattern you've probably experienced:

    1. 1Google "merge CSV files online" and find a tool
    2. 2Upload starts... 10%... 25%... 50%...
    3. 3Either: "File size exceeds limit" OR upload times out OR browser crashes
    4. 4Repeat with a different tool. Same result.

    This happens because most CSV tools use server-side processing. They need to upload your file before they can do anything with it. And hosting large file uploads is expensive, so they cap it at 50-100MB.

    Typical Tool Limits (That Block You)

    Most online CSV tools
    50-100 MB per file
    Google Sheets import
    100 MB (and 10M cells)
    Excel Online
    100 MB file size
    Many paid SaaS tools
    250 MB on expensive plans
    carbonapps Merge CSV
    No limit - browser memory only

    What Doesn't Solve It

    ✕

    Splitting files manually

    Time-consuming, error-prone, and you still need to merge the splits somewhere.

    ✕

    Paying for a premium account

    Usually just raises the limit to 250MB-500MB. Still not enough for multi-GB datasets.

    ✕

    Installing desktop software

    Works, but requires installation, setup, and often costs money. Overkill for a one-time merge.

    ✕

    Learning Python or command-line tools

    Steep learning curve for non-technical users. Not practical for quick tasks.

    No Upload = No Limit

    Process CSV files directly in your browser. Files never upload anywhere. The only limit is your computer's RAM.

    Select CSV files from your computer (no upload)
    Files are read and processed locally by JavaScript
    Merge happens in browser memory - no server involved
    Download the merged result - any size your browser can handle
    Works with files up to several GB (depending on your RAM)

    How Browser Processing Works

    Modern browsers can handle large files using the File API and Web Workers. Here's what happens:

    1. File Reading

    Files are read from your disk into browser memory using FileReader API. No network transfer.

    2. CSV Parsing

    JavaScript parses CSV data in memory. Handles quoted fields, escaped characters, and different encodings.

    3. Merging

    Rows are combined in memory according to your merge type (vertical stack or horizontal join).

    4. Download

    Merged data is converted back to CSV format and downloaded directly from browser memory. No server involved.

    Performance Notes

    • •File size: Can handle files totaling several GB on a modern computer with 8GB+ RAM
    • •Processing speed: 100MB files typically merge in 5-10 seconds
    • •Browser tab: Keep the tab active during processing for best performance

    Try It With Your Large Files

    No upload. No file size limits. Free forever. Works in your browser.

    Merge CSV Files Now

    Related Resources

    Excel Row Limit

    Over 1 million rows?

    Google Sheets Cell Limit

    Hit the 10 million cell limit?