What is Fixed Bids?

Fixed bids is the Sponsored Products bidding strategy in which Amazon uses your bid as entered. There is no real time increase or decrease for predicted conversion likelihood. The only thing that changes the bid is your own campaign settings.

What still applies

Fixed does not mean unmodified. Placement modifiers still multiply the bid, because a modifier is a setting rather than a prediction.

Effective bid = Base bid × (1 + Placement modifier)

So a fixed campaign with a 100 per cent top of search modifier is bidding twice its base figure in that placement, every time, with no variation. An hourly dayparting schedule, which works by rewriting the stored bid, also still applies.

Why anyone chooses it

Control and attribution. With fixed bids there is exactly one variable you own and one price you pay, so when performance moves you can say what caused it. Under the dynamic strategies, a change in cost per click may be your edit or may be Amazon's model reacting to something invisible to you, and the two cannot be separated after the fact.

That makes fixed the right setting whenever the purpose of the campaign is to learn something: testing a match type, measuring a placement's true economics, or establishing what a keyword is actually worth before automation is pointed at it.

What it costs you

You pay your bid on weak auctions as well as strong ones. Amazon will not step back from a query it judges unlikely to convert. The work that down only was doing for you has to be done another way, which means match type discipline, negative keywords and regular search term review carry more weight on a fixed campaign than on any other.

The house view

Shurq's doctrine defaults to fixed bids and dynamic down only, with the shaping done through placement modifiers and hourly schedules rather than delegated to a real time model. The reasoning is that a modifier is measurable and reversible, and a prediction made inside an auction is neither. Fixed is the cleaner half of that pair, and down only is the protective half.

Comparing the three

Whichever you choose, keep it consistent within a campaign for long enough to read the result, and compute your target bids from realised cost per click rather than from the setting itself.