Split Large CSV
Automatically split large CSV files into smaller parts for faster, more reliable imports with improved browser performance.
Overview
Uploading very large CSV files can cause browser slowdowns, high memory usage, or upload timeouts — especially when files contain thousands of rows.
The Split Large Files feature solves this by automatically dividing large CSV files into smaller parts and processing them sequentially behind the scenes.
Each part:
Preserves the original headers and column structure
Reuses the same column mappings automatically
Is processed independently for improved reliability
Remains grouped under a single parent import for easier tracking
This makes large imports significantly more stable and easier to manage.
When does file splitting activate?
File splitting activates only when all of the following conditions are met:
The uploaded file is a CSV file (
.xlsxExcel files are not currently supported)Split Large Files is enabled for the sheet
The uploaded file exceeds the configured Rows per Import limit
Admin Configuration
The feature can be enabled per-sheet from:
Sheet Settings → Import Steps
1. Split Large Files
Split Large Files
Yes / No
No
Enable this setting to automatically split large CSV uploads into smaller parts.
When disabled, the entire CSV file is processed as a single upload.
2. Rows per Import
Rows per Import
Number
1000
Defines the maximum number of rows processed in each part.
Example
If a CSV contains 4,500 rows and the limit is set to 1,000 rows, CSVBox will process the file in:
Part 1 → Rows 1–1000
Part 2 → Rows 1001–2000
Part 3 → Rows 2001–3000
Part 4 → Rows 3001–4000
Part 5 → Rows 4001–4500
Choosing the right value
Faster processing per upload
Fewer total parts
Lower browser memory usage
Higher memory usage
Better reliability for large datasets
Faster overall completion for moderate files
For most use cases, 1,000–5,000 rows per part works well.
3. User Confirmation Between Parts
User Confirmation
No / Yes / No, only if there are no errors
No
Controls whether users must manually continue between parts.
Available Modes
No
All parts upload automatically
Yes
User must confirm before each next part uploads
No, only if there are no errors
Upload continues automatically unless a part contains validation errors
For the smoothest experience, we recommend using No.
End User Experience
Step 1 — Upload a CSV File
The user uploads a CSV file normally through the importer.
If the file exceeds the configured row limit, CSVBox automatically prepares the file for multipart processing.
Step 2 — Split Notification
Before processing begins, the user sees a notification such as:
Large file detected We'll split this file into smaller parts (X rows each) for smoother processing. Each part will be uploaded automatically, and your column mappings will be reused.
The user can then:
Start Upload — Continue processing
Cancel — Cancel the upload
Step 3 — Map Columns (First Part Only)
The first part behaves exactly like a normal CSVBox import.
The user:
Maps columns
Reviews data
Fixes validation issues if needed
Submits the import
CSVBox automatically reuses the same mappings for all remaining parts.
The user does not need to map columns again.
Step 4 — Automatic Processing of Remaining Parts
After the first part is submitted, remaining parts are processed automatically.
A progress indicator shows overall upload progress.
Example
Depending on the confirmation mode, the user may or may not be prompted between parts.
Step 5 — Import Completion
Once all parts finish processing:
The multipart upload is marked as completed
All parts remain grouped under a single parent import
Users can review part-level details if needed
Viewing Multipart Imports
Multipart uploads appear as a single grouped import in the All Imports page.
CSVBox automatically tracks:
Overall import status
Number of processed parts
Row counts
Failed or partial parts
Multipart Import Statuses
Success
All parts processed successfully
Processing
Upload is still running
Partial Failure
Some parts failed
Failed
Entire upload failed
Viewing Part Details
Opening the import details shows information for each individual part.
Part
Part sequence number
Status
Success / Failed / Processing
Rows
Rows processed in that part
Import ID
Individual import reference
Errors
Validation or processing errors
Import Limits & Billing
Multipart uploads count as a single import toward your plan limits.
For example:
A 10-part upload = 1 import
A 50-part upload = 1 import
Individual parts are not counted separately.
Reliability & Error Handling
Each part is processed independently for improved stability.
This means:
A failure in one part does not invalidate already completed parts
Failed parts can be retried individually
Successfully processed parts remain intact
If a Part Fails
If a part encounters validation errors or processing failures:
The multipart upload is marked as Partial Failure
Error details are available for the failed part
Successfully processed parts remain unaffected
If the Browser is Closed Mid-Upload
If the browser closes before processing completes:
Completed parts remain saved
Remaining parts stop processing
The upload status reflects the completed progress
We recommend keeping the browser open until the upload finishes.
Limitations
Excel Files Are Not Supported
Currently, multipart processing supports CSV files only.
Excel (.xlsx) files are processed as a single upload regardless of size.
If needed, convert Excel files to CSV before uploading.
Maximum Parts Per Upload
To ensure reliable processing, a single upload can generate up to 100 parts.
If the configured row limit would exceed this number, the upload will stop with an error message.
In this case:
Increase the Rows per Import value
Or split the source CSV manually before uploading
Best Practices
For optimal performance:
Use CSV files instead of Excel for very large datasets
Keep row limits between 1,000–5,000
Enable automatic uploads when possible
Use smaller part sizes for slower devices or lower-memory environments
FAQ
Do all parts use the same column mapping?
Yes. Once the first part is mapped, CSVBox automatically reuses the same mapping for all remaining parts.
Are parts sent separately to destinations?
Yes. Each part is processed independently and sent separately to the configured destination.
Can users retry failed parts?
Yes. Failed parts can be retried individually without re-uploading the full file.
Can I disable this feature for specific users?
No. The feature is configured per sheet, not per user.
If different users require different behavior, create separate sheets with different settings.
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