Open the comparison tool before you buy, not after you regret. The checklist is five items and takes five minutes.
- Expense ratio: the only fee you pay with certainty, every year - Actual holdings, because similar names can own very different stocks - Overlap with your portfolio, where most people quietly fail - Tracking difference: how closely it follows the index after costs - Fund size and age; tiny new ETFs sometimes close, and a closure is a forced taxable event - Liquidity: thin trading and wide spreads are a hidden fee the expense ratio never shows
That five-minute check is exactly what Overlap ($4.99 one-time) does: fees, holdings overlap, returns, one screen.