Formatters & Code
Free Email List Cleaner & CSV Batch Splitter
Clean, dedupe, and split email list CSVs for Klaviyo, Mailchimp, and HubSpot locally. Fix EU semicolon delimiters and filter role emails with zero uploads.
Email list & platform settings
Drop your CSV or TXT file here, or browse
100% Client-Side Privacy • Zero Data Uploads • Max 25 MB
Results
What the result means
Email list imports fail when delimiters are mismatched, headers contain trailing whitespace, or lists exceed ESP batch thresholds. This tool parses CSV and TSV files locally using web workers without transmitting contact data over the network. It auto-detects column separators, identifies the primary email column, trims surrounding whitespace, lowercases addresses, and removes invalid syntax under RFC 5322. Deduplication retains either the earliest or most recent entry, while role accounts (such as admin@ or info@) and disposable email domains can be isolated into separate quarantine files. Clean contacts are then partitioned into platform-tailored batches (such as 25,000 rows for Klaviyo or 40,000 for Mailchimp) and packaged as individual CSVs or a single ZIP archive.
Related tools
Guides
Questions
Does customer or subscriber data leave my browser?
No. All CSV parsing, delimiter conversions, deduplication, and batch splitting execute entirely inside your local browser using Web Workers. Zero bytes of contact data are sent to our servers or stored anywhere.
Why do Klaviyo and Mailchimp imports fail with delimiter errors?
European versions of Microsoft Excel and LibreOffice export CSV files using semicolons (;) rather than commas. Most marketing automation platforms expect comma-delimited files, causing them to read the entire row as a single unparseable column.
How does deduplication choose which row to keep?
By default, the cleaner preserves the latest row encountered in the file, ensuring that updated customer tags, purchase dates, or subscription preferences take precedence over older records. You can also configure it to keep the first row.
What are role-based emails and why quarantine them?
Role-based emails (such as admin@, sales@, or info@) belong to departments or distribution groups rather than individuals. Blasting marketing campaigns to role emails significantly increases spam complaints, hurting your sender domain reputation.