Zero Snippet

CSV deduplicator for mailing lists, CRM exports, and product feeds

Use this free CSV deduplication tool when you need to remove duplicate rows from spreadsheet exports—by email, SKU, order ID, or any combination of columns. Paste comma-, semicolon-, tab-, or pipe-delimited text, or upload a file. Processing runs entirely in your browser, so subscriber lists and inventory files are not sent to a server for deduping. Choose keep first or keep last when keys repeat, optionally trim whitespace for fair comparisons, then copy or download a cleaned UTF-8 CSV ready for Mailchimp, HubSpot, Shopify imports, or SQL loaders.

Delimiter: Auto (Comma)
Delimiter
On duplicate rows

Columns used for duplicate detection

Rows match if every selected column matches. With none selected, the entire row must match to count as a duplicate.

Deduplicated CSV

Data rows: 4 in → 4 out

Why deduplicate CSV files before imports?

Duplicate rows inflate bounce risk in email campaigns, skew analytics in ad audiences, and break uniqueness constraints in databases. Marketing automation platforms often charge by contact count, so a clean deduplicated mailing list saves money and protects sender reputation. E-commerce teams merge vendor catalogs and marketplace exports; deduping on product SKU or GTIN keeps feeds consistent for Google Merchant Center and internal PIM workflows. Doing this step before you run CSV to SQL inserts or sync to a CRM reduces failed batches and support tickets.

How to use this CSV deduplicator (step by step)

  1. Paste or upload your export. If cells contain commas inside quotes (for example "Acme, Inc.",US), keep the quotes—the parser treats them as one field.
  2. Set Delimiter to Auto unless you know the file uses a fixed separator (common for EU semicolon CSV and tab-separated files).
  3. Enable First row is header when the top row names columns so checkboxes show meaningful labels like email or sku.
  4. Under Columns used for duplicate detection, check every field that must match for two rows to count as duplicates. Example: only email for contacts, or brand + part number for spare parts. Clear all boxes to dedupe when the entire row is identical.
  5. Toggle Trim values when comparing to ignore leading and trailing spaces in keys—recommended for email and phone columns extracted with our email extractor.
  6. Choose Keep first (default) or Keep last depending on which row should win when keys repeat.
  7. Click Copy CSV or Download .csv. For JSON pipelines afterward, use our CSV to JSON converter or round-trip with JSON to CSV.

Column keys vs full-row deduplication

Selective column deduplication is ideal when the same person or product appears more than once but auxiliary fields differ—notes, import batch, or campaign tags. With every column checked, two rows must match across all those fields to count as duplicates (after optional trimming)—the usual approach for exact spreadsheet duplicates. Clear all column checkboxes to treat the entire padded row as one key, which matches only when the full line is the same. For plain text without CSV columns, our duplicate line remover works on raw lines instead of parsed cells.

Delimiters, locales, and data hygiene

Excel and Google Sheets often export locale-specific CSV: semicolons in many European locales, commas in US-style files. Tab-separated values appear in analytics and scientific exports. Auto detection inspects the first lines to pick a stable separator. After deduping, you can normalize line endings or split fields further with our comma separator tool when preparing data for other tools.

Privacy and performance

Parsing and duplicate detection run locally in your browser—useful for GDPR-sensitive lists, unreleased catalog updates, and large spreadsheets you do not want to upload to third-party SaaS. Very large files may hit browser memory limits; split by segment or year if needed. Preview columns in your spreadsheet app first if you are unsure which fields form the natural duplicate key.

Related file and data tools

Browse the full File & data tools section on the home page, or open a nearby utility below.

  • CSV Viewer & Editor — Open CSV as a sortable, filterable table, tweak cells, and export without a spreadsheet app.
  • CSV to SQL Converter — Generate INSERT statements from a CSV for quick database seeding and migrations.
  • Image to Base64 Converter — Encode images to Base64 data URIs for embedding in HTML, CSS, or API payloads.
  • Image Resizer — Resize by pixels or percentage in the browser—privacy-friendly, no server upload required.
  • Image Compressor — Shrink JPG and PNG with quality control and before/after size stats for faster pages.
  • Image Format Converter — Convert between JPG, PNG, and WebP locally to match CMS, email, and performance needs.
  • Image Metadata Viewer — Inspect EXIF: camera, lens, GPS, dimensions, and exposure—great for photographers and forensics.
  • File Hash Checker — Compute MD5, SHA-1, and SHA-256 hashes of uploads to verify downloads and integrity.
  • SVG Optimizer — Minify and clean SVG markup to cut file size for icons, illustrations, and inline graphics.

Frequently asked questions

What does CSV deduplication mean?
Deduplication removes extra rows that match on the columns you care about. For example, if two rows share the same email address but differ in a notes column, you can select only the email column so one row is kept and the other is dropped. The tool preserves your header row and outputs a clean CSV you can import into CRMs, ESPs, or databases.
Does this tool upload my CSV to a server?
No. Parsing, duplicate detection, and export run entirely in your browser. Files stay on your device, which is important for mailing lists, customer data, and unreleased product feeds. For other local file workflows, see our CSV viewer and CSV to SQL tools in the File & Data Tools section.
Should I keep the first or the last duplicate row?
Keep first is typical for newsletter lists and lead imports when the earliest subscription or signup row is authoritative. Keep last is useful when later rows contain corrected phone numbers, updated SKUs, or refreshed timestamps and you want the newest values to win. You can switch modes without re-uploading the file.
What is “trim values when comparing”?
When enabled, leading and trailing spaces are ignored when building the duplicate key. That way email@example.com and email@example.com with accidental spaces are treated as the same contact. Turn it off if whitespace is meaningful in your dataset (for example fixed-width codes).
Which delimiters are supported?
You can use comma, semicolon, tab, or pipe—or leave delimiter on Auto so the tool inspects the first lines and picks the most consistent separator, matching how European CSV exports and TSV files are often saved.
How do I dedupe by multiple columns?
Check every column that must match for a row to count as a duplicate—such as first name plus last name plus postal code. The tool builds a composite key from all selected columns, so only rows that match on every selected column are collapsed.
Can I remove completely identical rows only?
Yes. Select all column checkboxes (the default) so the duplicate key includes every field. Rows must match in full to be considered duplicates—useful after merging exports or concatenating spreadsheets.
How is this different from the duplicate line remover?
The duplicate line remover treats each line as plain text. This tool understands CSV structure: quoted fields, delimiters inside quotes, and column-based keys. Use the text tool for logs or code; use the CSV deduplicator for tabular data and mailing lists.