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 (.xlsx Excel 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

Setting	Options	Default
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

Setting	Type	Default
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

Smaller Parts	Larger Parts
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

Setting	Options	Default
User Confirmation	No / Yes / No, only if there are no errors	No

Controls whether users must manually continue between parts.

Available Modes

Mode	Behavior
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

Processing (2/5)

2,000 / 5,000 rows processed

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

Status	Meaning
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.

Column	Description
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.