---
title: "Ad server vs DSP: what each does and where Epom fits"
description: "How an ad server and a DSP differ, why they are complementary, and how Epom's ad server auctions your direct campaigns against the DSP partners you plug in."
type: "concept"
audience: [network-manager, admin]
keywords: [ad server, DSP, demand-side platform, SSP, OpenRTB, RTB, demand partner, direct campaign, programmatic, auction, do I need a DSP]
---

Fetch the complete documentation index at: https://epom.com/ad-server/docs/llms.txt. Use this file to discover all available pages before exploring further. Append .md to any documentation page URL to get its markdown version.

# Ad server vs DSP: what each does and where Epom fits

"Ad server" and "DSP" get used as if they were rival products you have to choose between. They
are not — they do different jobs, and Epom uses both at once. Epom **is** an ad server, and a
DSP is a bidder you plug into it. This page explains the split in plain terms and shows exactly
where each one sits in Epom, so you can answer the real question: *do I need to add a DSP, or is
Epom already enough?*

## The short version

- An **ad server** stores your inventory and creatives, decides which ad wins each request, and
  logs the result. It is the referee and the record-keeper. **Epom is the ad server.**
- A **DSP (demand-side platform)** is a buyer's tool. It shops for impressions across many
  supply sources and **bids** on the ones it wants, in real time. In Epom, a DSP is an external
  **partner** whose bids compete inside the same auction Epom already runs.

You always have an ad server (Epom). A DSP is optional extra demand you connect to it.

## What the ad server does — Epom’s job

When a page, app or player requests an ad, Epom's ad server runs one fixed pipeline
([how ad selection works](https://epom.com/ad-server/docs/concepts/how-ad-selection-works.md)):

1. **Resolves the placement** and gathers the demand linked to it.
2. **Filters** that demand by pre-targeting, targeting, capping, limits and format fit.
3. **Ranks and picks** a winner by priority tier, then campaign, then banner.
4. **Generates the markup**, substitutes macros, attaches tracking, and returns it.
5. **Logs** the impression, click and conversion so it shows up in Analytics.

Everything you build in the account area — advertisers, campaigns, banners, sites, zones,
placements — is demand and supply that this ad server owns and serves directly. That is the
whole [quick-start walkthrough](https://epom.com/ad-server/docs/start/quick-start-network.md): no DSP involved.

## What a DSP does — the buyer’s side

A DSP works for advertisers, not publishers. Its job is to *buy* impressions programmatically:
it receives bid requests describing an impression (the user, the site, the format), decides how
much that impression is worth to its advertisers, and returns a **bid** with a price and a
creative. It never stores your inventory or runs your auction — it just answers "here's my
price for this one impression."

In Epom you don't operate a DSP; you **connect to** one as an OpenRTB demand partner (your network
administrator configures it under [DSP partners](https://epom.com/ad-server/docs/guides/admin/dsp-partners.md)). The pre-built partner types
Epom ships (TrafficStars, ExoClick, Kadam, TwinRed and others) plus the plain-OpenRTB
*Custom DSP Endpoint* type are all examples of this: external bidders you invite into your
auction.

> **Note:** the mirror-image term is **SSP (supply-side platform)** — the seller's programmatic
> tool. When Epom sends a bid request to a DSP partner, Epom is acting as the SSP for that
> exchange. You don't configure a separate SSP; the ad server plays that role.

## Where they meet: two demand sources, one auction

The point that makes Epom coherent is that direct campaigns and DSP partners are **both just
demand** to the same ad server. When the pipeline picks a winner, a programmatic banner is not a
finished creative — it is a placeholder for an auction:

- If the pick lands on a **direct** banner, Epom serves your stored creative.
- If the pick lands on an **OpenRTB (DSP) banner**, Epom fires bid requests to the eligible DSP
  partners, collects their bids, drops any creative that
  [creative scanning](https://epom.com/ad-server/docs/use-cases/creative-policy-protection.md) has blocked, and serves the winning bid's
  creative. The winner pays its own bid (first price) unless a second-price setting applies, and
  a bid below the bid floor never wins — see
  [first vs second price](https://epom.com/ad-server/docs/concepts/auction-first-vs-second-price.md).
- If **no acceptable bid** comes back, Epom excludes the programmatic banners and re-runs the
  pick over the remaining direct demand in the same priority tier, then the tiers below it — so a
  dead auction still fills with your own ads when it can.

So your direct sales and your DSP demand compete for the same impression under the same rules
(priority, targeting, floors). The ad server is the single referee; the DSP is one more bidder
at the table.

## "Do I need both?"

| Your situation | What you need |
|---|---|
| You sell your own inventory to your own/direct advertisers | The ad server (Epom) alone. Build advertisers, campaigns, banners; link and serve. |
| You have unsold inventory and want programmatic demand to fill it | The ad server **plus** one or more DSP partners connected via OpenRTB. |
| You want direct deals to take priority and programmatic to backfill | Both — put direct campaigns in a higher [priority tier](https://epom.com/ad-server/docs/concepts/how-ad-selection-works.md#7-priority-tiers-then-campaign-then-banner) than the OpenRTB banners. |
| You are a pure buyer with no inventory | A DSP is the buyer's tool; Epom's ad server is a seller/network platform. Different job. |

The common case for an Epom network is **both at once**: your direct campaigns carry the
premium demand and DSP partners monetise whatever direct demand doesn't fill — all decided in
the one auction.

## Corner cases

> **Corner case:** priority still beats price across the boundary. A high-priority direct
> campaign outserves a DSP bid even when the DSP would pay more, because eCPM ranking runs only
> *inside* one priority tier. If you want your direct floor price to genuinely compete with
> programmatic, put the direct campaign and the OpenRTB banners in the *same* tier.

> **Corner case:** the banner's own **Pricing** card offers CPM alone for an OpenRTB banner,
> whatever your CPC/CPA permissions — what it earns is the auction price, not a price list you
> type in. The event a *partner* pays on (CPM, CPC or CPI) is a separate setting on the DSP
> partner. See [OpenRTB DSP banners](https://epom.com/ad-server/docs/guides/advertising/banner-openrtb-dsp.md).

> **Corner case:** connecting a DSP is a network administrator's action, not a demand-user one. Advertisers
> and network managers pick from the partners that already exist; they can't add a bidder
> themselves. The network administrator works in **Admin → Demand partners (DSP) → DSP partners**, or hands the
> same screens to network staff through the account's **RTB** tab (three *RTB Management*
> permissions, all shipped disabled). If a partner you expect is missing from the banner's DSP
> list, it either hasn't been configured there or has been deactivated — a deactivated partner is
> not offered.

## Related

- [DSP partners](https://epom.com/ad-server/docs/guides/admin/dsp-partners.md)
- [How ad selection works](https://epom.com/ad-server/docs/concepts/how-ad-selection-works.md)
- [OpenRTB / DSP banners](https://epom.com/ad-server/docs/guides/advertising/banner-openrtb-dsp.md)
- [Protect your inventory from bad creatives and bad traffic](https://epom.com/ad-server/docs/use-cases/creative-policy-protection.md)
- [Quick start: serve your first ad](https://epom.com/ad-server/docs/start/quick-start-network.md)
- [Glossary](https://epom.com/ad-server/docs/reference/glossary.md)