The Bid Optimizer manages the bids of all your keywords on a daily basis. For new keywords, it builds up the bid step by step. For keywords that are already performing, it adjusts based on your target ACOS.
The Bid Optimizer is the automation that manages your bids every day. It does this for every keyword in your campaigns, but in a different way depending on how far along a keyword is. Keywords that haven’t received any clicks yet are built up. Keywords that are already performing are adjusted based on actual results. All within the limits you set yourself via your rule set.
The Bid Optimizer automatically recognizes which phase a keyword is in and adjusts its approach accordingly.
Keywords without clicks A new keyword starts with a starting bid but doesn’t have any data yet. The system doesn’t know yet whether the keyword is profitable. What it does know is that the keyword needs visibility to be able to determine that. The Bid Optimizer therefore increases the bid every day by your set change rate, until the keyword starts generating clicks or reaches the max. CPC.
This continues as long as the keyword has zero clicks. As soon as clicks start coming in, the system automatically switches to the second approach.
Keywords with data As soon as a keyword has gathered enough clicks or spend, the Bid Optimizer calculates what the bid should have been to land exactly on your target ACOS. Is a keyword losing money? The bid goes down. Is it converting better than your target? The bid goes up.
Every day in two rounds:
At 2:00 PM the keywords without clicks are processed. At 3:00 PM the keywords with data are processed.
You don’t have to do anything for this. The system itself determines which keyword falls into which round.
For keywords without clicks
The bid is increased every day by your set change rate. If the current bid is €0.50 and your change rate is 10%, then the new bid will be €0.55. This repeats daily until clicks come in or the max. CPC is reached.
For keywords with data
The system calculates the difference between what you spent and what you were allowed to spend based on your target ACOS:
Loss = spend - (sales x max. ACOS)
If the loss is positive, you spent more than your target allowed. The bid goes down. If the loss is negative, you’re performing better than your target. The bid goes up. If the loss is zero or there are no clicks, the bid stays the same.
The loss or profit is then converted per click and added to or subtracted from the average CPC over the past 7 days:
With loss: new bid = average CPC - (loss / clicks) With profit: new bid = average CPC + (profit / clicks)
The system always works on 7 days of data, not on a single day. That makes the calculation more stable and less sensitive to outliers.
An example: you spent €12, there is €30 in sales, and your max. ACOS is 25%.
Loss = €12 - (€30 x 0.25) = €12 - €7.50 = €4.50
The loss is positive: the bid goes down.
Suppose your max. ACOS was 50% with the same figures:
Loss = €12 - (€30 x 0.50) = €12 - €15 = -€3
The loss is negative: the bid goes up.
A keyword with data is included if, in the past 7 days, it meets at least one of these three situations:
You’ve spent more than your set max. keyword budget, but there have been no sales.
The keyword has reached more clicks than your click threshold, but there have been no sales.
The keyword has more clicks than your click threshold and the actual ACOS is above your max. ACOS.
In addition to these triggers, these basic conditions always apply: the keyword is set to ENABLED, the match type is EXACT or PHRASE, the ad group is set to ENABLED, and the campaign has an active ruleset with all required settings filled in. Broad match keywords are not included; they’re too broad to base reliable ACOS conclusions on.
After the new bid is calculated, the system checks three protections. These are always applied in this fixed order, for both keywords without clicks and keywords with data.
1. Change rate If the calculated change is bigger than your set change rate, the adjustment is capped at that maximum percentage. This prevents one week of bad data from completely messing up a keyword.
2. Max. CPC The bid is compared to your max. CPC. If it’s above that, it’s brought back down to your max. CPC.
3. Min. CPC Finally, it’s checked whether the bid stays above your min. CPC. If it’s below, it’s increased to your min. CPC. This protection always wins, even if the calculation or the change rate would justify a lower bid.
The Bid Optimizer works entirely through the ruleset you link to a campaign. Without an active ruleset, the Bid Optimizer doesn’t do anything with that campaign.
Max. ACOS This is your goal. The Bid Optimizer calculates everything back to this number. Set it to what your product can actually handle commercially, not what you wish it could be. A max. ACOS that’s too low will make the system keep lowering bids, even on keywords that are profitable in the long run.
Click threshold The minimum number of clicks a keyword needs to have before the Bid Optimizer steps in based on data. For most categories, a threshold between 10 and 30 clicks works well.
Max. keyword budget The maximum spend per keyword as an extra trigger. If a keyword reaches this amount without a single sale, the system steps in, even if the click threshold hasn’t been reached yet.
Change rate The maximum percentage by which a bid is allowed to change per day. This applies both to increasing bids for new keywords and adjusting based on data. A change rate of 10 to 20% is a good starting point for most situations.
Min. CPC The bid will never drop below this value. Make sure it’s high enough to stay visible in the Bol auction.
Max. CPC The bid will never rise above this value. This is your absolute upper limit, even for keywords without clicks that are being increased step by step.
