When You Need to Split Files
You have a massive text file—maybe millions of lines. Your target system only accepts files under a certain size. Or you need to distribute work across multiple processes. Or your email service limits how many addresses you can import at once.
Desktop tools exist but often crash on large files. Online services upload your data to unknown servers. Command-line utilities require technical knowledge.
We built this splitter to handle massive files efficiently, entirely in your browser. Your data never leaves your device, and you get all split files in a convenient ZIP download.
Three Split Modes
By Line Count
Specify exactly how many lines each file should contain. Perfect when you need consistent batch sizes.
- 10,000 lines input, 1,000 lines per file = 10 files
- 10,500 lines input, 1,000 lines per file = 11 files (last file has 500)
- Best for: Import limits, batch processing, consistent workloads
By File Count
Specify how many output files you want. Lines are distributed as evenly as possible.
- 10,000 lines input, 4 files = ~2,500 lines each
- 10,003 lines input, 4 files = files with 2501, 2501, 2501, 2500 lines
- Best for: Distributing work to N workers, creating N test batches
By File Size
Specify maximum file size in MB. Each output file stays under this limit.
- 50MB input, 10MB max = 5+ files depending on line lengths
- Useful when target systems have upload size limits
- Best for: Email attachment limits, upload restrictions, storage constraints
Practical Use Cases
Email List Management
Most email services limit import batches. Split your master list into chunks of 500 or 1,000 addresses, then import each file separately.
Parallel Processing
Divide data across multiple workers or threads. Use "By File Count" mode to create exactly the number of batches matching your parallel capacity.
API Rate Limits
APIs often limit requests per batch. Split your data into chunks that fit within rate limits, process each file separately with delays between batches.
Storage Constraints
Some systems limit file sizes. Use "By File Size" mode to ensure each split file meets your storage system's requirements.
Options Explained
- Output Prefix: Filename prefix for split files (default: "split")
- Remove Duplicates: Deduplicate all lines before splitting
- Randomize Before Split: Shuffle lines before distributing to files
- Trim Lines: Remove leading/trailing whitespace
- Skip Empty Lines: Ignore blank lines in input
Workflow Tips
Combine this tool with others for complete data processing:
- Remove duplicates first to clean your data
- Filter to keep only relevant lines before splitting
- Combine files if you need to merge them back later
Performance and Privacy
Everything runs in your browser. Files are read in 4MB chunks to handle large inputs without memory issues. The ZIP file is generated client-side using JSZip.
Frequently Asked Questions
What are the three split modes?
By Line Count: Each file gets exactly N lines. By File Count: Splits into exactly N files with lines distributed evenly. By File Size: Each file stays under the specified MB limit.
How do I download all split files at once?
Click the 'Download All (ZIP)' button to get all split files in a single ZIP archive. You can also download individual files by clicking the download icon next to each file.
What happens if my file doesn't divide evenly?
The last file will contain the remaining lines. For example, splitting 1000 lines by 300 lines per file creates 4 files: three with 300 lines and one with 100 lines.
Can I randomize before splitting?
Yes. Enable 'Randomize Before Split' to shuffle all lines before dividing them into files. This is useful for creating randomized test batches.
What file naming convention is used?
Files are named using the prefix you specify followed by a 4-digit number: prefix_0001.txt, prefix_0002.txt, etc. Change the Output Prefix field to customize naming.