> For the complete documentation index, see [llms.txt](https://docs.relevant-digital.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.relevant-digital.com/hb-manager/integrations-and-connections/hbm-and-prebid-server.md).

# HBM and Prebid Server

## What Is Prebid Server, and When Do You Need It

**Prebid Server (PBS)** is an open-source solution — Relevant Digital runs its own Go-based fork — that shifts the work of calling multiple demand partners (SSPs) from the user's browser to a high-performance server. It's the shared engine behind three otherwise-separate integration paths: **AMP** (which has no client-side JavaScript at all), **Mobile App** (the stored-request/resolved-request mechanics covered in Mobile App Integration), and optional **server-to-server** bidding on ordinary web pages.

If you've read either of those sections already, you've been using PBS without a dedicated page for it until now — this section documents the engine itself.

### The three call types (web context)

On a standard web page, you can run Prebid one of three ways:

| Type                  | What happens                                                          | When to use                                                                 |
| --------------------- | --------------------------------------------------------------------- | --------------------------------------------------------------------------- |
| **Client-Side Only**  | Traditional browser-based bidding — every bidder called from the page | The default; no server involvement                                          |
| **Server-Side Only**  | Every configured bidder is called via PBS instead of the browser      | Once you're confident in server-side performance                            |
| **Parallel (Hybrid)** | Both run simultaneously, client and server bids compete               | Recommended for initial testing — lets you compare safely before committing |

### Reported benefits — and the honest caveat

Moving bidder calls server-side can mean: more bidders competing without loading down the browser, faster page speed from fewer HTTP requests, fewer client-side timeouts, and access to demand integrations that only exist server-side.

**None of this is guaranteed automatically.** Actual performance improvement depends on your specific bidder mix, traffic, and page weight — it needs to be verified with A/B testing (the Parallel/Hybrid mode above is exactly how you'd run that test) rather than assumed from the general pitch.


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