CSV File Splitter

Split large CSV files with progressive record increases

Split Large CSV Files Online Free & Secure

CSV File Splitter is a powerful, free online tool designed for email marketers, data analysts, and business professionals who need to divide large CSV files into smaller, manageable segments. Whether you're preparing contact lists for email campaigns, splitting customer databases for team distribution, or organizing data for CRM imports, our tool handles files of any size with complete privacy—all processing happens in your browser.

100% Private

Files never leave your computer. All processing happens locally in your browser.

Lightning Fast

Process millions of rows in seconds with our optimized client-side engine.

No File Limits

Split files of any size without restrictions. No signup or payment required.

Easy to Use

Simple three-step process: upload, configure, download. No technical skills needed.

Start Splitting Your CSV Files

Upload your file below to get started. All processing happens in your browser—your data never leaves your device.

Upload Mode
Choose between single file or dual file merge mode
Upload CSV File
Select a CSV file to split into multiple smaller files
Split Configuration
Configure how you want to split your CSV file

Split with increasing record counts per file

Number of records in the first file

Percentage to increase records for each subsequent file

Files will be named: output_part001.csv, output_part002.csv, etc.

Shuffle the CSV rows randomly while preserving the header row. Useful for creating randomized datasets.

Frequently Asked Questions
Everything you need to know about splitting and merging CSV files. Can't find what you're looking for? Check our detailed how-to guide for step-by-step instructions.

Splitting a CSV file with our tool is straightforward. First, click the file upload button and select your CSV file from your computer. The file will be loaded into your browser's memory (not uploaded to any server). Next, choose your split mode: Progressive Split creates files with increasing record counts, while Even Split divides records equally. Configure your parameters—for Progressive Split, set the initial record count and percentage increase; for Even Split, specify the number of output files. Finally, click the 'Split CSV File' button. Your files will be generated instantly, and you can download them individually or as a ZIP archive.

Yes, CSV File Splitter includes a powerful dual-file merge feature specifically designed for email marketers. Switch to 'Dual File (Merge & Split)' mode using the toggle at the top of the tool. You'll see two upload areas: one for your 'Opener Data' (contacts who open emails) and one for your 'Clicker Data' (contacts who click links). Upload both CSV files—they must have the same column structure. Then choose a merge strategy: 'Mix Evenly' alternates rows from both files throughout the output, while 'Front-load Clicker Data' places 75% of clicker data in the first file. After merging, the combined data is split according to your configured settings.

Progressive Split and Even Split are two different approaches to dividing your CSV data. Progressive Split creates files with increasing record counts based on a percentage you specify. For example, if you set 1,000 initial records with a 10% increase, your first file contains 1,000 records, the second contains 1,100 records, the third contains 1,210 records, and so on. This is ideal for email campaign warm-up where you want to gradually increase sending volume. Even Split, on the other hand, divides your total records equally across a specified number of files. If you have 10,000 records and request 5 files, each file will contain approximately 2,000 records. This is perfect for A/B testing, team distribution, or batch processing where you need equal segments.

How CSV File Splitter Works

Splitting your CSV files takes just three simple steps. No account required, no software to install, and no technical expertise needed. Get started in seconds.

1

Upload Your CSV File

Select your CSV file from your computer. The file is loaded directly into your browser's memory—it's never uploaded to any server. You can also use our dual-file mode to merge two CSV files before splitting.

2

Configure Split Settings

Choose your split mode (Progressive or Even), set the initial record count and percentage increase for progressive splits, or specify the number of output files for even splits. Enable randomization if you need unbiased distribution.

3

Download Your Files

Click the split button and watch as your files are generated instantly. Download individual files or grab everything as a convenient ZIP archive. Your split files are ready for immediate use in your campaigns or workflows.

Technical Details

Supported File Formats

CSV File Splitter accepts standard CSV (Comma-Separated Values) files with any delimiter. The tool automatically detects headers in the first row and preserves them in all output files. UTF-8 encoding is fully supported for international characters.

Browser Compatibility

Our tool works in all modern web browsers including Chrome, Firefox, Safari, and Edge. Since processing happens client-side using JavaScript, you need a browser that supports the File API and Blob downloads. No plugins or extensions required.

Performance Considerations

File processing speed depends on your computer's memory and processor. Most files under 100MB process in seconds. For very large files (500MB+), we recommend using a desktop computer with at least 8GB RAM for optimal performance.

Data Security

Your files are processed entirely in your browser using client-side JavaScript. No data is ever transmitted to our servers or any third party. When you close the browser tab, all file data is automatically cleared from memory.

Powerful Features for Data Professionals

CSV File Splitter offers a comprehensive set of features designed to handle any CSV splitting or merging task. From simple file division to complex merge strategies, we've got you covered.

Progressive Split Mode
Create files with progressively increasing record counts, perfect for email campaign warm-up strategies. Start with a small batch and gradually increase volume to build sender reputation and improve deliverability rates.
Even Split Mode
Divide your CSV file into equal-sized segments for A/B testing, team distribution, or batch processing. Specify the number of files you need, and our tool automatically calculates the optimal record distribution.
Dual File Merge & Split
Combine two CSV files (like opener and clicker lists) before splitting. Choose from merge strategies including even mixing or front-loading high-engagement contacts for maximum campaign effectiveness.
Data Randomization
Shuffle your records randomly before splitting to ensure unbiased distribution across output files. Essential for creating statistically valid A/B test groups and preventing systematic bias in your campaigns.
Bulk ZIP Download
Download all split files as a single ZIP archive for convenient organization. Each file is named sequentially (part001, part002, etc.) with your custom filename prefix for easy identification.
Complete Privacy
Your data never leaves your device. Unlike cloud-based tools, CSV File Splitter processes everything locally using JavaScript in your browser. No uploads, no servers, no data retention—guaranteed privacy.

Who Uses CSV File Splitter?

Our tool serves professionals across industries who need to manage, organize, and distribute large datasets efficiently. Here are some common use cases from our users.

Email Marketing Campaigns
Email marketers use CSV File Splitter to prepare contact lists for campaign deployment. Split large subscriber databases into smaller batches to comply with ESP sending limits, warm up new IP addresses with progressive sends, or create segmented lists for targeted messaging.
Campaign warm-up sequencesESP upload limits complianceSubscriber segmentation
A/B Testing & Analytics
Data analysts and marketing teams rely on our tool to create statistically valid test groups. Use even split with randomization to divide contacts into equal, unbiased segments for testing subject lines, send times, content variations, or landing pages.
Subject line testingSend time optimizationContent variation tests
Team Workload Distribution
Sales managers and team leads use CSV File Splitter to distribute leads and contacts among team members fairly. Split prospect lists evenly to ensure balanced workloads, or use progressive split to assign more contacts to senior team members.
Lead distributionTerritory assignmentSales quota allocation
CRM Data Migration
IT professionals and database administrators use our tool when migrating data between CRM systems. Split large export files into manageable chunks that meet import limits, ensuring smooth data transfers without timeout errors or system overloads.
Salesforce importsHubSpot migrationsDatabase transfers
E-commerce Operations
Online retailers and e-commerce managers split customer databases for targeted promotions, loyalty programs, and personalized marketing. Segment customers by purchase history, location, or engagement level for more effective outreach.
Customer segmentationLoyalty program managementRegional campaigns
Research & Academia
Researchers and academic institutions use CSV File Splitter to prepare datasets for analysis. Split large survey responses, experimental data, or research databases into manageable portions for statistical analysis or collaborative review.
Survey data processingResearch collaborationStatistical sampling