Conversion Upload Checker is a free tool I built with Bolt to check a Google Ads offline conversion import file before you upload it. Its checks come from Google's own help pages and CSV template, and the few heuristics are labelled as heuristics. It catches an unfilled time zone line, wrong column names, day-first dates, conversions past Google's 90-day click limit, rows with no click ID, email or phone, bad consent values, duplicates, and plain emails or phones that may still need hashing (always shown masked). It also lists what a file can't prove, such as the real click time, and lets you download only the rows with no errors. Everything runs in your browser and nothing is uploaded. Try it: https://conversion-upload-checker.bolt.host