At my previous startup, CSV import was make-or-break for customer onboarding. We built the first version in three days. Then reality hit: Windows-1252 encoding, European date formats, embedded newlines, phone numbers in five different formats.

We rebuilt that importer multiples over the next six months. Our onboarding completion rate dropped 40% at the import step because users couldn't fix errors without starting over.

The real problem isn't parsing (PapaParse is excellent). It's everything after: mapping "Customer Email" to your "email" field, validating business rules, and letting users fix errors inline.

Flatfile and OneSchema solve this but won't show pricing publicly. Most open source tools only handle pieces of the workflow.

ImportCSV handles the complete flow: Upload → Parse → Map → Validate → Transform → Preview → Submit. Everything runs client-side by default. Your data never leaves the browser. This is critical for sensitive customer data - you can audit the code, self-host, and guarantee that PII stays on your infrastructure. The frontend is MIT licensed.

Technical approach

We use fuzzy matching + sample data analysis for column mapping. If a column contains @ symbols, it's probably email.

For validation errors, users can fix them inline in a spreadsheet interface - no need to edit the CSV and start over. Virtual scrolling (@tanstack/react-virtual) handles 100,000+ rows smoothly.

The interesting part: when AI is enabled, GPT-4.1 maps columns accurately and enables natural language transforms like "fix all phone numbers" or "split full names into first and last". LLMs are good at understanding messy, semi-structured data.

GitHub: https://github.com/importcsv/importcsv Playground: https://docs.importcsv.com/playground Demo (90 sec): https://youtube.com/shorts/Of4D85txm30

What's the worst CSV you've had to import?

Flowering time and pollinator visits shape which plants thrive each season

Huawei develops AI inference solution to reduce reliance on foreign HBM chips

AI models need a virtual machine

ABD Online Directory Discover Alabama's Automotive, Retail, Healthcare,Travel

I Taught Myself to Vibe Code: A Free Bootcamp

Light detection in blind human retina using ultra-sensitive human ion channels

Executing Untrusted Code in Serverless Environments

Show HN: Community-Powered Product Launch

Show HN: OpenAnimation – KMP app for exploring and editing Lottie animations

Show HN: Clone of a Macintosh-Like Computer with a Built-In Basic Interpreter

2x Performance, $300k Savings: Rewriting a Critical Service in Rust at TikTok

Art Index in ShannonBase

Guide to Contrastive Learning: Techniques, Models, and Applications

Musk's xAI sues engineer for allegedly taking secrets to OpenAI

Today's game consoles are historically overpriced

Nearly 900k Cars Sold: Toyota's Record July Proves Strategy Works

Potassium-rich diet may cut risk of heart failure by 24%

Bcachefs Goes to "Externally Maintained"

ResumeAI 2.0

Fishermen Pulled in an Orange Shark Off Costa Rica: 'My God, What Is This?'

The AI Productivity Paradox- Chopping Wood Cubed

Nobel Prize and a Testy Phone Call: How the Trump-Modi Relationship Unraveled

Show HN: Reactylon – An open-source framework for building 3D/XR apps with React

Cognitive Load is what matters

Proposals for commercial planes to operate single pilot shelved after EU report

Build Your Own Htmx

Show HN: I built an open-source CSV importer that I wish existed

Not in my browser Vivaldi capo doubles down on generative AI ban

AMD Ryzen CPUs fry twice in the face of heavy math load, GMP says

FBI cyber cop: Salt Typhoon pwned 'nearly every American'

Show HN: Keeptalking