Why login screens kill MVPs
Signup forms typically shed the majority of first-time visitors — Baymard's checkout research puts abandonment at ~70% [1] and product-led onboarding studies land in a similar range. Gating your MVP before anyone has seen the product means you're optimising the wrong funnel — you can't fix retention if nobody got past the door. [1] https://baymard.com/lists/cart-abandonment-rate
What to do instead
Let users do the core thing immediately. Save their work in localStorage. Ask for an email only when they want to save permanently, share, or unlock a second feature. We did exactly this on Fuel Finder — zero login, instant value.
When you do need auth on day one
B2B tools where the user's company expects SSO. Anything storing personal data. Apps with social/collaborative features. For everything else, defer it.
The metric to watch
Time-to-value: seconds between landing and 'oh, that's useful'. Under 10 seconds is the bar. A login screen alone takes longer than that.