How ads pay

How does a free game earn?

Garden Defense is free to download. So how does it pay for itself? With ads. Advertisers pay to show them, and a share of that money comes to us.

Google runs two ad programs: AdSense for websites and web games, and AdMob for phone apps like Garden Defense. Both work the same way, in five steps that happen in less than a second.

Five steps, in under a second

• 1. Make a spotWe add an ad unit: a place where an ad may appear, like after a level.
• 2. Ask for an adThe game tells Google: "one player is looking at this spot. Who wants it?"
• 3. Lightning auctionAdvertisers' computers bid in milliseconds. The best bid that follows our rules wins.
• 4. The ad showsThe player sees it. That is one impression.
• 5. PaydayGoogle keeps a share and pays the studio's bank account monthly, once we have earned at least US$100.

Ad words to know

• ImpressionOne ad shown to one player, one time.
• CPMMoney per 1,000 impressions. M is "mille", Latin for thousand.
• eCPMWhat we actually earned per 1,000 impressions. The number that matters.
• Fill rateHow often Google found an ad for our spot. 80% means 1 in 5 requests stayed empty.

Bolt says: For normal website ads, Google says publishers keep about 68% of what advertisers pay.

Three kinds of game ads

• Banner: use with careA thin strip at the edge. Keep it far from buttons so nobody taps it by accident.
• Interstitial: use with careFull screen between levels. Only at natural breaks, never mid-battle.
• Rewarded: fairThe player chooses to watch for a bonus. Feels like a deal, and usually pays the most.

Bolt says: This website is free, and the occasional card labeled "Ad" after a finished lesson helps pay for it. Notice it never appears inside a lesson, and any link that leaves the site asks a parent first.

Rules for games kids play

• Family-safe ads onlyGames aimed at kids must follow each store's family rules: only approved ad networks, and no personalized ads based on tracking what kids do. Laws like COPPA (US) and GDPR (Europe) protect children's data (Stage 4 covers them in Keeping player data safe).
• An adult holds the accountAdSense and AdMob account holders must be 18 or over, because the terms are a contract about getting paid. The company owns the account, and a parent signs up with us.
• Never click your own adsAdvertisers pay for real players. Google treats clicks from the studio as invalid activity and can close the account for good.

Bolt says: Ad and store rules change often, so check the latest version with a parent before launch. Next lesson: bank accounts and taxes, where the ad money lands.