Create Holdout Groups & A/B Test Segments Instantly
Free tool to split customer lists into 2-10 random groups with custom ratios. Perfect for email campaign testing, holdout analysis, and controlled experiments. 100% privacy-safe - all processing happens in your browser.
Drag-drop or select your Klaviyo export file. The tool can handle any size from 100 rows to 1M+ rows, limited only by your browser memory.
Choose how many groups you want (2-10) and set your holdout percentage (0-50%). For example, a 20% holdout with 3 test groups means each test group gets 26.7% of the list.
The tool uses the Fisher-Yates shuffle algorithm to randomly shuffle and split your list into perfectly random, unbiased groups. All processing happens in your browser—your data never leaves your device.
Download a ZIP file containing all split CSV files plus a summary document showing exact counts and percentages. Upload the groups back to Klaviyo as separate segments for testing.
Processing speed: 100k rows in under 10 seconds
Perfect for A/B testing (2 groups) or multi-variant testing (3-10 groups). Each group gets an equal share of your list with perfectly random distribution.
Set aside 10-50% as a control group that doesn't receive your campaigns. This lets you measure true incremental lift and prove campaign ROI vs. baseline behavior.
Uses the Fisher-Yates shuffle algorithm for cryptographically unbiased randomization. Unlike manual splitting, eliminates human error and ensures scientifically valid test groups.
All processing happens in your browser using JavaScript. Your customer data NEVER leaves your device, uploads to servers, or gets exposed to third parties. Fully GDPR compliant.
Handle files with 100 to 1,000,000+ rows, limited only by your browser memory. Works with all CSV formats from Klaviyo, Shopify, and other platforms.
If you set a 20% holdout with 3 test groups, each test group automatically gets 26.7% and the holdout gets 20%. The tool handles the math for you.
All groups packaged in one convenient ZIP file with a summary document showing exact row counts and percentages for each group.
Completely free tool with no account creation, no email required, no credit card, and unlimited uses. Just upload and split.
Split your list into 2-5 groups to test different subject lines, send times, offers, or creative approaches. Measure which variation drives the best results.
Create a 10-30% control group that doesn't receive your campaigns. Compare their behavior vs. test groups to measure true incremental lift and prove campaign ROI.
Split subscribers to test different automation flow sequences and message timing. Measure which flow variant drives higher conversion and engagement.
Split large lists into smaller batches to avoid sending spikes that trigger email provider throttling or deliverability issues.
Test 3-10 different campaign variations simultaneously with perfectly equal distribution. Ideal for testing multiple creative concepts or messaging angles.
Unlike manual splitting or sorting by characteristics, the Fisher-Yates algorithm ensures perfectly unbiased groups with zero human error. Essential for valid A/B testing.
Holdout groups let you prove incremental value vs. baseline customer behavior. Show exactly how much revenue came from the campaign vs. what would have happened anyway.
Proper A/B testing requires random assignment, not segmenting by demographics or behavior. This tool ensures scientifically valid experiment design.
Unlike cloud-based CSV tools, your customer data never uploads to third-party servers. No risk of data breaches, leaks, or unauthorized access.
Optimize your Klaviyo account with our complete suite of free tools.
Identify and remove inactive profiles to reduce Klaviyo costs by 20-30%
Deploy proven email flow templates (abandoned cart, winback, thank you)
Create perfectly random test groups in seconds. 100% privacy-safe with all processing in your browser.
Launch List Splitter Tool →