I Built a 100MB Browser-Based CSV Cleaner After Getting Frustrated With Messy CRM Exports

I kept running into the same issue: messy CSV exports from CRMs. Duplicates. Blank rows. Extra whitespace. Broken email columns. For smaller files, Excel works fine. But once files get larger, cleanup becomes repetitive and time-consuming. So I decided to build a small browser-based tool to automate the common cleanup steps. The Idea I wanted something that: Supports large files (up to 100MB) Removes duplicate rows Trims whitespace Cleans email formatting Works entirely in the browser Doesn’t store files The goal wasn’t to replace Excel or Power Query — just to simplify quick cleanup. Technical Challenges Handling large files in the browser is tricky. Some things I had to consider: Memory usage Streaming file processing Efficient duplicate detection Keeping UI responsive during processing I ended up using streaming techniques to avoid loading everything into memory at once. What I Learned Many CSV issues are repetitive and predictable Most cleanup workflows are 3–4 repeated steps Perfo