I usually start with test events to make sure all the key actions View Content, Add to Cart, Initiate Checkout, Purchase are firing correctly.
After that I compare Shopify orders with Meta or TikTok conversions over a longer period rather than day by day. Its normal for the numbers to differ because of attribution windows ad blockers and privacy settings.
As long as the events are firing correctly and the overall trends are consistent I dont worry too much about getting a perfect 1:1 match.
comparing pixels against each other is the part that trips most people up, because Meta and TikTok are both lossy in the same direction, so a match between them doesn’t prove either one is right. the only complete source you have is Shopify orders themselves, since those are server side and don’t drop to ad blockers or ITP.
so the check I trust is direction. a pixel should always show fewer purchases than Shopify orders for the same window, never more. if a platform reports more conversions than you had orders, that’s usually double firing (the theme pixel plus an app both sending purchase), not good coverage.
the other useful number is the gap between your browser pixel and the server side Conversions API for the same platform. that gap is basically your ad blocker plus ITP loss rate, and watching it over time tells you if tracking is degrading. for a real spot check I just take one known order id and confirm it shows up in each platform’s event manager, instead of trusting the aggregate count.
what does your Shopify orders number look like next to the pixel for the same day, higher or lower?