Hey Product Hunt! 👋 My actual workflow: I get a lot of CSV/Excel files (many from college), and I want to analyze them with ChatGPT/Claude. Two things always annoyed me: 1. I want to control exactly which rows/columns I hand to the AI — not upload the whole file blindly. 2. I just want a quick sum of some numbers without writing =SUM() first. So I made LazySheet, a fast, local-first desktop viewer for spreadsheets. Local-first means your files never leave your machine — no upload, no cloud, no account, no telemetry. It even works fully offline. The only thing that ever leaves your computer is the exact range you choose to copy into the AI. That's the whole point: you decide what the model sees. The features I actually use: - Copy as Markdown — select a range, copy, paste into the AI. Clean table, model reads it perfectly. - Instant aggregates — select cells, the sum shows up. No formula needed. - Opens big files fast — only renders visible rows, so 100MB CSVs don't lag. - Column filters, group-by summaries, find-in-sheet. Reads .xlsx / .xlsm / .xls / .csv / .tsv. Free, runs on macOS / Windows / Linux. 🔗 https://lazysheet.brata.cloud Early release — happy to take feature requests or feedback. What would make this part of your workflow?

LazySheet

Fast. Simple. Spreadsheet Viewer.

Fast. Simple. Spreadsheet Viewer.