Drop any CSV up to 100 MB. Trim whitespace, detect data types, remove empty rows, deduplicate — all processed locally. Nothing ever leaves your device.
What it does
Most CSV files that leave a database, CRM or spreadsheet tool carry invisible damage. LeanCSV fixes the six most common problems in one pass — no code, no installs, no server.
Strips leading and trailing spaces from every cell. The most common cause of failed joins and broken lookups — fixed in under a second regardless of row count.
Convert any column to UPPERCASE, lowercase or Title Case. Standardize product codes, city names, status fields and email addresses before they hit your pipeline.
Detects and deletes rows and columns where every cell is blank — artifacts of copy-paste or deleted content that inflate row counts and break schema validation.
Samples up to 200 values per column and classifies each as number, date, boolean or text. Colour-coded badges re-run after every operation.
Removes exact duplicate rows in one pass. The stats bar shows the count before you commit so you know exactly what's about to be deleted.
Renders up to 100 rows per page with sticky typed headers. Scroll, inspect and verify the data before exporting — all inside the browser tab.
Use cases
Real-world CSV files come from dozens of sources and each introduces its own class of dirt. Here are the situations where LeanCSV saves the most time.
Before importing into PostgreSQL, MySQL or SQLite you need clean types and no stray whitespace — otherwise VARCHAR columns get padded values, integer casts fail, and UNIQUE constraints throw on near-duplicates that differ only by a trailing space.
Salesforce, HubSpot and Mailchimp exports frequently contain duplicate contacts, inconsistent capitalisation and empty rows from deleted records. Deduplicate and normalize case in seconds before importing into a new system or running a mail merge.
Excel and Google Sheets exports often include ghost columns with invisible formatting characters and accidental rows below the data range. Remove Empty Rows/Cols clears these in one click and gives you a row count you can trust.
Want to audit an input file before it hits the transformation stage? LeanCSV gives you an instant structural scorecard — column count, type per column, empty ratios, duplicate count — without writing a single line of code.
Legal, financial and healthcare CSVs can't be uploaded to a third-party service without compliance review. Because LeanCSV runs 100% in your browser with no network activity during processing, it's safe with PII, financial records and protected health information.
Shopify, WooCommerce and Magento exports often contain blank SKU rows, inconsistent category casing and duplicate product IDs. Clean the feed in the browser and upload a valid file directly to the next platform.
Why LeanCSV
Most CSV tools either require an upload, a subscription, or a Python environment. LeanCSV has none of those dependencies.
Everything runs inside your browser tab. There is no upload, no queue, no API call. The only latency is your CPU parsing text.
The CSV parser, type detector and all cleaning logic are hand-written vanilla JavaScript. No npm, no bundler, no library to audit.
Your file content is never transmitted. Not to our servers, not to analytics, not anywhere. It's a guarantee baked into the architecture, not a policy.
Every feature — trim, deduplicate, type detection, export — is available to everyone with no account, no daily limit and no watermark on the output.
Comma, semicolon, tab or pipe — LeanCSV sniffs the delimiter from the first 4 KB of the file and preserves it in the exported output.
Number, date, boolean or text — detected on load and refreshed after every operation so the table always reflects the current state of the data.
FAQ
Yes, completely. No premium tier, no feature gating, no account. LeanCSV is part of the RuntimeHub suite of free browser-native tools.
No. Your file is read by the browser's FileReader API and handed to a Web Worker running locally in your tab. No network request is made at any point during processing. Verify it yourself: open DevTools → Network and watch it stay empty.
LeanCSV automatically detects the delimiter from the first 4 KB of the file. Supported: comma (,), semicolon (;), tab (\t) and pipe (|). The detected delimiter is preserved in the exported file.
Up to 100 MB. Files above 10 MB are read in 4 MB streaming chunks to keep memory stable. A 500 MB limit is planned for a future Pro tier.
Yes. The parser handles RFC 4180-style quoting: fields wrapped in double quotes, delimiters inside quoted fields, and escaped double quotes (""). Both CRLF and LF line endings are supported.
Each column is sampled — up to 200 non-empty values — and tested against regex patterns for numbers, ISO dates, and boolean values. A column is only classified as a non-text type if at least 85% of sampled values match the pattern, preventing false positives on mixed data.
Deduplication compares raw cell values — whitespace included. For whitespace-insensitive deduplication, run Trim spaces first, then Deduplicate. This gives you explicit control over what counts as a duplicate.
Not yet — there's no multi-step undo stack currently. Each operation is applied to the in-memory dataset immediately. Click Reset and re-upload to start over. Your original file on disk is never modified.
Any modern browser with Web Workers and ES6: Chrome 80+, Firefox 75+, Safari 14+, Edge 80+. For best performance on large files, Chrome or Edge on desktop is recommended.
It's on the roadmap. For now, export your Excel file as CSV first — every major spreadsheet tool supports this in one click.