Ad Waterfall: How Publishers Can Fill More Ad Space and Earn More

Nov 04, 2026 | Akriti Bhatnagar

An ad waterfall is a system that ranks ad networks or ad sources in priority order, usually by expected eCPM, and offers each ad request to them one at a time until one fills it. Every empty ad slot is money you didn’t earn, and every ad that sells too cheaply is money you gave away. The ad waterfall is one of the oldest ways publishers deal with both problems. It lets you line up several networks so that if one can’t fill an impression, the next one gets a chance. It’s simple and it still works, but it has limits, especially next to bidding. This guide explains how a waterfall works, what its tiers and types are, where it falls short and how publishers can fill more ad space and earn more with it.

What is an ad waterfall?

An ad waterfall is a list of ad sources, each in its own tier, ranked from highest expected pay to lowest. When your app or page asks for an ad, the request goes to the top tier first. If that source fills the request, the ad shows and the process ends. If it can’t, or its price is below your minimum, the request drops to the next tier, and so on down the list. In practice, a mediation platform or ad server runs this for you. Each source is usually ranked by its historical eCPM, meaning its past average earnings per 1,000 impressions. Read our eCPM guide if you need a refresher.

How does an ad waterfall work?

Here’s a simple example. The numbers are illustrative, not benchmarks.

A user opens a screen with an ad slot, and your app sends an ad request.
Tier 1: Network A ranked highest at an expected $8 eCPM. It has no ad to fill, so it passes.
Tier 2: Network B, expected $6. It fills the request, so the ad is shown.
The process stops. Networks C and D never see this request.
For the next ad request, the process starts again from the top.

Mediation platforms can also set a minimum price per tier. A network only shows an ad if it meets or beats that minimum.

What are the lines (tiers) of an ad waterfall?

Each “line” or tier in a waterfall holds a few things:

The ad source: a specific network or an instance of one.
Its priority: its position in the order.
Its price floor or expected eCPM: the number that decides where it sits.
A fallback tier at the bottom: a lower-paying source that fills slots nobody else wanted, so space doesn’t go empty.

You can usually override the automatic order and set manual rates. That helps when you want to push a source up or down based on what you know about it.

What are the different types of ad waterfalls?

Neither of the main guides defines formal types, so here’s a practical way to group them:

Manual (static) waterfall: you set the order and prices yourself and change them by hand. It gives full control, but it takes ongoing work.
Dynamic waterfall: the platform ranks sources by recent eCPM and updates the order automatically. This is what most mediation platforms do by default.
Hybrid waterfall: bidding runs alongside the waterfall. Real-time bidders compete with the waterfall tiers, and the highest value wins. Most publishers are heading here.

Ad waterfall on the web vs in mobile apps

The idea is the same in both, but the tools differ:

In apps, a mediation platform manages the waterfall, so you integrate one SDK instead of one per network.
On websites, ad server priorities and “passback” rules do the same job, sending an unfilled request to the next source.

If you’re comparing platforms for apps, see our best mobile app monetization platforms guide.

What are the benefits of an ad waterfall?

More fill. Several sources behind one slot means fewer empty impressions.
Simple to understand. The logic is easy to follow and explain.
Control. You decide the order and the minimum prices.
Wider reach. You can work with networks that don’t support bidding.
One integration point. In apps, a mediation SDK covers many networks.

What are the limits of an ad waterfall?

The order is based on history, not live bids. A source ranked lower might have paid more for a particular impression, but it never gets the chance if a higher source fills first.
It’s slow. Requests go one at a time, so each ad can take longer to appear.
It needs upkeep. Prices move, so the order goes stale unless someone updates it.
Less competition. Sources aren’t fighting for the same impression, so you may miss the highest price.

Ad waterfall vs header bidding and in-app bidding

	Ad waterfall	Header bidding / in-app bidding
How the winner is picked	First source in order that fills the request	Highest bid in a real-time auction
Competition	Sequential	All sources at the same time
Pricing	Based on past eCPM and set floors	Based on live bids
Speed	Slower, since calls run one by one	Usually faster, since calls run at once
Upkeep	Regular manual tuning	Less manual ordering
Network support	Works with networks that don’t bid	Needs bidding-enabled partners

For a deeper look at the bidding side, read our header bidding guide and real-time bidding platforms guide.

How can publishers fill more ad space and earn more with a waterfall?

Order tiers by recent, real eCPM, not old numbers. Check them regularly.
Set floors by country and format. One floor for everything leaves money behind in strong markets and blocks fill in weak ones.
Add fallback tiers so no slot goes empty.
Keep the list lean. Too many tiers add delay, and a source that rarely fills is just latency.
Set sensible timeouts so a slow network doesn’t hold up the whole request.
Test one change at a time and compare with your baseline.
Review the setup often. Prices and demand shift over time. Our ad revenue optimization guide has more tips.

When should you move to bidding, or go hybrid?

Look for these signs:

Fill is good but eCPM has stalled.
You spend a lot of time reordering tiers by hand.
Ads load slowly because requests pass through many tiers.
You suspect lower-ranked sources would pay more for some impressions.

A hybrid setup lets you keep the networks that only work through a waterfall while adding bidding for competition.

How do you migrate step by step?

Record your baseline: eCPM, fill rate, latency and revenue by country and format.
Add bidding alongside your waterfall, not instead of it.
Start with a share of traffic or a few placements.
Compare results, including load speed and user metrics.
Shift more traffic as the results hold up.
Keep waterfall tiers as a fallback for sources that don’t bid.

How MagicBid can help

MagicBid helps publishers monetize through mediation and bidding, so multiple demand sources compete for your impressions. If you’d like help setting up a hybrid waterfall, or want to see where your current one is leaving revenue behind, see our web monetization service. For app-specific tuning, read our mobile ad performance guide.

FAQs

What is an ad waterfall?

A system that ranks ad networks by expected eCPM and offers each ad request to them in order, until one fills it.

What are the lines of the waterfall?

They’re the tiers in the list. Each one holds an ad source, its priority and its price floor or expected eCPM, with a fallback at the bottom.

What is the waterfall concept?

It’s a top-to-bottom flow. In advertising, the ad request goes to the highest-priority source first and falls to the next only if the first can’t fill it.

What are the different types of waterfalls?

Manual (you set the order), dynamic (the platform orders by recent eCPM) and hybrid (waterfall combined with bidding).

What does waterfall mean in funds?

That’s a finance term for the order in which investors and managers are paid from a fund’s returns. It’s a different concept from an ad waterfall.

How many networks should a waterfall have?

There’s no fixed number. Enough to keep slots filled, but not so many that extra tiers add delay for little return.

Is the ad waterfall outdated?

Not entirely. It still helps with networks that don’t support bidding, but bidding often earns more, so many publishers run both.

Does an ad waterfall slow down my site or app?

It can, because requests go one at a time. Fewer tiers, sensible timeouts and bidding alongside it help.

Keep the Waterfall Working for You

An ad waterfall is a simple way to fill more ad space, but the order only helps if it reflects what sources actually pay today. Keep the tiers lean, update the floors, add fallbacks and watch speed. When the waterfall starts holding you back, add bidding alongside it, instead of replacing everything at once. If you’d like a second opinion on your setup, talk to MagicBid. magicbid.ai

If you’re not making the most of your ad space, you’re leaving money on the table. MagicBid helps web, app, and CTV publishers maximize revenue with smarter ad placement and optimization tools.

Web Monetization: Get better ad visibility, higher engagement, and more revenue from every impression.
In-App Monetization: Connect with premium advertisers to effortlessly boost fill rates and eCPMs.
CTV Monetization: Deliver high-quality, tailored ad experiences that keep viewers engaged and advertisers paying more.

With MagicBid’s advanced ad tech and expert support, you can turn your traffic into higher earnings without the guesswork. Connect with us now to get a free ad revenue evaluation.