Prebid.js is open source. You can download it, pick your adapters, build it and host it yourself for nothing. That fact makes the build option look far cheaper than it is, because the download is the easy part.
What building actually commits you to
- A build pipeline. Prebid is compiled per adapter set. Every bidder you add or drop is a rebuild, a test and a deploy.
- Release cadence. Prebid releases frequently. Falling behind means missing bidder fixes; upgrading blind means breaking things. Somebody has to read changelogs regularly.
- Consent plumbing. TCF 2.0, CCPA, GPP, and the changes to all three. This is compliance work, not feature work, and it does not stop.
- Ad server line items. Generating and maintaining price-priority line items across granularity changes and currency handling.
- Analytics. Prebid gives you events, not reporting. Bid density, timeout rate and win rate per bidder are all things you have to build a pipeline to see.
- Performance engineering. Lazy loading, adaptive timeouts, viewability gating, refresh discipline. Each is a project, and each is where the actual money is.
- Unfilled recovery. Entirely on you. Prebid has no opinion about what to do with an impression nobody bid on.
- Debugging under pressure. When revenue drops 30% on a Saturday, the person who understands the wrapper needs to be reachable.
When building is right
When you have at least one engineer whose actual job is ad technology, revenue large enough that a percentage point is worth a salary, unusual requirements no platform serves, or a strategic reason to keep the capability in house. Large publishers build for good reasons and it works well for them.
When a platform is right
When your engineers are better spent on your product, when you want the performance work already done rather than on a roadmap, or when you cannot carry the on-call risk of a revenue-critical system nobody owns.
The honest framing: a platform is not cheaper than free software. It is cheaper than the engineer who maintains the free software, and it is faster than the eighteen months it takes to learn what that engineer needs to know.
What to ask a vendor
- 1 Do I keep my own Ad Manager network and my own SSP contracts? If no, understand exactly what you are handing over.
- 2 How do you charge, and does it change if my CPMs improve? Flat fees say no.
- 3 Can I export my configuration and my reporting? Lock-in is usually a data problem, not a contract problem.
- 4 What is the actual page weight and main-thread cost of the tag? Ask for a number and verify it yourself.
- 5 How long does a configuration change take to go live? Days means someone is doing it by hand.
- 6 Who do I reach at 9pm on a Saturday when revenue drops?
- 7 What happens to my setup if I leave? "Remove the script" is the right answer.
Ask every candidate the same seven questions and write the answers down. The differences between vendors show up far more clearly in the answers to these than in any deck.
The middle option people forget
You do not have to choose permanently. Running a platform while your team learns the domain is a legitimate strategy, and so is keeping a platform for the long tail of your sites while building for the flagship. Since your SSP contracts are the durable asset, keeping those in your own name is what preserves the option either way.
Related questions
Is Prebid.js free to use?
The library is free and open source. Running it in production is not: you take on the build pipeline, frequent version upgrades, consent compliance, ad server line item maintenance, analytics, performance engineering and out-of-hours debugging. The software costs nothing; the ongoing engineering is the real price.
How much engineering time does a self-hosted Prebid setup need?
Plan for meaningful ongoing capacity rather than a one-off project — Prebid releases frequently, bidder requirements change, and consent frameworks evolve. Most publishers who build successfully have at least one person for whom ad technology is a named responsibility, not a side task.
What is the biggest risk of using a header bidding platform?
Lock-in through ownership rather than contract: if the vendor holds your Ad Manager network or your SSP relationships, leaving means rebuilding your demand from scratch. Keep the network and the contracts in your own name and the platform becomes replaceable, which is the position you want to negotiate from.
Can I switch header bidding platforms later?
Yes, if you kept your own Ad Manager network and SSP contracts — then switching is swapping a script and re-entering configuration. If a vendor holds the demand relationships, switching means reapplying to every SSP and waiting weeks for approvals. That difference is worth more than most feature comparisons.
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