As others have mentioned, none are accurate. That being said, I kinda like Humbleworth conceptually because it attempts to give different values for auction/marketplace/brokered sales (even if they're mostly wrong). I've seen so many domains that would be appraised as being worth thousands of dollars fail to even get a 1$ bid at auction. The reason the sweet spot for mediocre domains is around 2000$ isn't because they're worth that much... It has more to do with the business model of resellers with large portfolios. They sell about 1% of inventory per year... at 10$ reg fee per domain per year, their average sale price per domain needs to be well above 1k + acquisition cost to even be profitable long-term. No matter how shitty your domain is, you'll be able to find a comparable past sale of 2000$. But if it wouldn't sell at auction right now, it's just a lottery ticket that expires in a year. More on reddit.com

Sounds good. I hope this stays alive long cause you know GD is limiting the number of appraisal right? More on reddit.com

It could do with some validation to check the user has provided a tld (.com etc)

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Sedo does manual appraisals (i.e. a human is involved). Human appraisals are superior to automatic ones, because humans are context-aware whereas machines are not. It is perfectly possible for Estibot or similar ilk to appraise an arguably worthless two-word combination in the high four digits because "cars.com" sold for for $987053890703 and "potatoes" gets 100m daily searches on Google and, therefore, potatoescars.com should be an excellent domain. But the problem with domain appraisals is that (a) they are subjective (b) beauty is in the eye of the beholder and (c) you can do a lot of the research yourself (comparable sales). Sedo does not publish the results of your appraisal, or even the fact of it, but you can share the appraisal through their system when communicating with your buyer through their portal as negotiating leverage. However, I would probably skip paying for their service and do the research myself. Also, be sure to not overestimate yourself. It is very easy to think you have a seven-figure domain, but, chances are, if you registered it yesterday, there was probably a reason for that. More on reddit.com