--- title: "What Is an Ad Server? Definition and Examples | RentAnOTT" description: "An ad server decides which ad to show for each request and records what was delivered. See what it does for a streaming service and where SSPs fit." url: "https://www.rentanott.com/glossary/ad-server" markdown_url: "https://www.rentanott.com/glossary/ad-server.md" category: "Advertising" updated: "2026-10-05" --- # What is an ad server? An ad server is the system that decides which ad to show each time a player or stitching service asks for one, delivers the details of that ad and counts the result. For a publisher it is the control center of an advertising business. ## What an ad server does - Stores campaigns: the creative, dates, budget and number of impressions sold - Targets: matches campaigns to audience, content, device, region and time - Decides: picks the best ad for each request according to priority and price - Paces: spreads a campaign's impressions across its dates - Caps frequency: limits how often one viewer sees one ad - Counts: impressions, quartiles, completions and clicks - Reports: delivery for advertisers and revenue for the publisher ## How a request is handled A request arrives describing the opportunity. The ad server first looks for a directly sold campaign that matches. If none qualifies, or if an auction might pay more, it offers the slot to programmatic demand through one or more supply-side platforms. The winner is returned as a VAST response. ## Ad server, SSP and DSP Several products combine an ad server and an SSP. A small service may start with a single ad network that performs all of these roles and add its own ad server once it sells advertising directly. - Ad server: the publisher's own decision and delivery system - SSP (supply-side platform): sells the publisher's unsold inventory to many buyers by auction - DSP (demand-side platform): the advertiser's tool for bidding on inventory across many publishers ## Ad server on RentAnOTT AVOD is included on every RentAnOTT plan. The advanced advertising add-on ($169/month) adds deeper targeting, frequency control and ad performance reporting, and ad platforms can be connected through premium integrations. [See pricing](https://www.rentanott.com/pricing). ## Related terms - [VAST](https://www.rentanott.com/glossary/vast) — VAST (Video Ad Serving Template) is the industry standard, published by the IAB Tech Lab, for how an ad server describes a video ad to a player. A VAST response is an XML document that tells the player which media file to play and which tracking addresses to call. - [Programmatic advertising](https://www.rentanott.com/glossary/programmatic-advertising) — Programmatic advertising is the automated buying and selling of ad impressions through software, in place of orders negotiated by sales teams. Each ad opportunity is offered to buyers and sold, often by auction, in the fraction of a second before the ad plays. - [Dynamic ad insertion](https://www.rentanott.com/glossary/dynamic-ad-insertion) — Dynamic ad insertion (DAI) is choosing which ads to show at the moment a viewer reaches an ad break, individually for that viewer, instead of permanently embedding the same ads in the video file for everyone. - [SSAI](https://www.rentanott.com/glossary/ssai) — SSAI (server-side ad insertion) is a way of delivering video advertising in which the ads are stitched into the stream on the server before it reaches the viewer. The player receives one continuous stream containing both program and ads. - [CSAI](https://www.rentanott.com/glossary/csai) — CSAI (client-side ad insertion) is a way of delivering video advertising in which the player on the viewer's device requests each ad from an ad server and plays it itself, pausing the program while the ad runs. - [Fill rate](https://www.rentanott.com/glossary/fill-rate) — Fill rate is the percentage of ad requests that are answered with an ad. If a service requests 1,000 ads and receives 700, its fill rate is 70%. Unfilled requests earn nothing. ## Further reading - [Add-ons](https://www.rentanott.com/features#addons) - [Content monetization platforms compared](https://www.rentanott.com/blogs/content-monetization-platforms) - [OTT revenue calculator](https://www.rentanott.com/tools/ott-revenue-calculator) ## Frequently asked questions ### Does a streaming service need its own ad server? Not at the start. An ad network can supply ads through a single tag. Your own ad server becomes worthwhile when you sell campaigns directly or use several demand sources. ### What is the difference between an ad server and an ad network? An ad network sells your inventory for you and sends back ads. An ad server is software you control that chooses between your own campaigns and outside sources. ### How does an ad server connect to a video player? Through a VAST tag, which the player or the server-side stitching service requests at each ad break. All 163 terms: [Streaming and OTT glossary](https://www.rentanott.com/glossary). ## Book a demo Tell RentAnOTT what you are launching. The team walks through the platform and maps the path to go-live around your catalog, markets and revenue model. Book a demo: https://www.rentanott.com/contact ## More from RentAnOTT - [Home](https://www.rentanott.com/index.md) — What RentAnOTT is, what every plan includes, and how launch works - [Features](https://www.rentanott.com/features.md) — Every core feature and optional add-on - [Pricing](https://www.rentanott.com/pricing.md) — Platform tiers, apps, add-ons, usage rates and example bills in INR and USD - [Free tools](https://www.rentanott.com/tools.md) — OTT app builder and calculators for streaming revenue, bandwidth, bitrate and pricing - [Insights](https://www.rentanott.com/blogs.md) — All streaming business articles - [Glossary](https://www.rentanott.com/glossary.md) — Definitions of streaming and OTT terms - [Book a demo](https://www.rentanott.com/contact.md) — Talk to RentAnOTT about your launch Full site in one file: https://www.rentanott.com/llms-full.txt