How many games are included in this data?

The database currently contains information about 881392 Ability Draft games, played between Aug 09, 2020 and Oct 27, 2020.

What's with some of the pairs that have a very high / very low win rate?

Calculating accurate win rates for all 100,000+ pairs of abilities requires a lot of data. With that many pairs, it is likely there are some that have gotten very "lucky" or "unlucky". So it is best not to trust those rates completely, at least until more games are played.

Especially when looking at pairs with the highest or lowest win rates, pairs with few games played are more likely to come up, not because they actually have a very high or low rate, but because small sample size means higher variance.

How is "synergy" calculated?

Somewhat arbitrarily. It is the difference between the combined win rate and the geometric mean of the individual win rates. It is intended to measure the strength of interactions, independent of their components. For example, Sticky Napalm and Ion Shell both have very average win rates individually, but they have high synergy, leading to a higher winrate when picked together.

Can you include information about pick order?

No, unfortunately Valve does not make this information available in their API.

Can I reverse the sort order, or sort by a different column?

Yes, click the column header.

Can I see the number of wins or losses, or a confidence interval for win rates?

Yes, hover over any win rate (or tap on mobile) to see wins, losses, and 95% confidence interval.

How is the confidence interval calculated?

I use the Jeffreys Interval. The win rate is modeled as ~ Beta(1/2 + wins, 1/2 + losses), and I give the locations at which the CDF of that distribution is 2.5% and at which it's 97.5%.

Who runs this website / how should I contact you with feedback?

My name is Joe Kelley. I've been programming for fun since 2006 and professionally since 2010. I've been playing DotA for fun since 2004, and still haven't gone professional. You can find links to all of the rest of my online presence on my website: Feel free to email me at