Dota 2 has broken its own record for the biggest esports prize pool ever.

The prize pool for this year's The International – Valve's annual Dota 2 esports tournament that is basically its World Cup – was US$20.9m at the time of publication.

This surpasses last year's record US$20.8m total, and there is with more than a month of crowdfunding to go.

For those not aware, Valve boosts The International's prize pool each year by releasing a paid "compendium" in-game app, also known as a Battle Pass.

It began the practice in 2013, and since then the Battle Pass has grown, as has its popularity.

The Battle Pass usually contains items like loot boxes, inside which are cosmetic items of extreme rarity, including effigies and map overhauls, new user-interfaces, and new voice lines.

It also contains a Dota fantasy league, wherein users draft players and set a line-up to earn points from match results.

There are even different levels of Battle Pass, which you can pay to unlock, or earn through an in-game wagering system.

This year, Level 1 sets you back US$10, while Level 75 is US$40. A mere 25 percent goes towards the prize pool, while Valve keeps the rest for itself.

In the Battle Pass this year is a brand-new quest path and cosmetic for Kunkka, a cosmetic that turns Io the Wisp into Portal’s Companion Cube, new announcers and taunts, integrated voice lines that let you play sound files of famous esports moments, and more.

A total of 18 teams take part in The International: six are invited, and 12 earn their place via regional qualifiers. This year, the tournament takes place at Seattle's KeyArena from August 7-12.

Dota 2 is the most popular game on Steam, and one of the most popular games in the world.