Why Vibel's numbers can differ from Shopify's own analytics

Both read the same orders, so a small, explainable gap is normal: timezone, refund timing, and which orders count (POS, drafts, test orders) are the usual reasons, not a tracking fault.

The short answer

Vibel and Shopify's own analytics both start from your Shopify order ledger, so they should never disagree wildly. When they differ, it is almost always one of a short list of honest reasons, not a tracking problem.

The usual reasons for a gap

1Timezone and day boundaries: a report drawing its 'today' boundary in your store's timezone versus UTC can place a handful of late-night orders in a different day, which shows up as a one-day shift, not a missing order.
2Refund timing: an order refunded after the sale can net differently depending on whether a figure is computed at the moment of sale or recomputed after the refund posted.
3What counts as an order: POS, draft, and app-created orders are handled explicitly rather than silently folded into the same bucket everywhere, because no browser pixel can ever see an order that never had a browser session, and counting those the same way as a tracked online order would misrepresent what tracking achieved.
4Currency and market splitting: a brand running several country stores can see Shopify's own per-store totals add up differently from a consolidated cross-market figure, depending on whether currency conversion happened before or after the number you are comparing.

When the gap is NOT one of these

A gap that is large, growing, or does not match any of the reasons above, rather than a steady small offset, is worth a support ticket with the exact two numbers and the date range you compared. That is a genuinely different class of problem from the explainable gaps above, and it is worth someone looking at your account specifically rather than guessing from a general answer.

Choosing an attribution model and a lookback window