An instant online estimate is the first thing most sellers check, and there is nothing wrong with that. It is a fine starting point. The mistake is treating it as an answer. An algorithm prices your home from public records and an average of nearby sales. It has never seen the inside.
What the algorithm is missing
The things that move price the most are the things an automated model cannot measure. A renovated kitchen versus an original one. A flat, usable backyard versus a steep slope. A quiet interior street versus a busy through-road. Morning light. A view. None of that lives in the public record, and all of it shows up in the final number.
It also cannot see demand. How many buyers are actively competing on your street this month is not a data point a model updates in real time, and in a market like Silicon Valley that single factor can swing an outcome by a wide margin.
What actually tells you the number
Two things. First, recent comparable sales within walking distance, read by someone who knows which of those homes was truly comparable and which had a hidden issue. Second, an honest read of your own home's condition and position against those comps. That is what a pre-listing strategy review is, and it is the difference between a guess and a number the market will validate.
If you want to start with the real market data for your city before going further, that is exactly what the home value page is for: current, sourced figures, and then a hand-written read on your specific home.
The number that matters is the one a real buyer will pay. An estimate that never walked through the front door is not that number.
Thinking about selling? Request a pre-listing strategy review.