How does bol's advertising system (Sponsored Products) really work?
Lars HurkmansCo-founder22 July 2026Temps de lecture 12 minutesBol's advertising system is an auction, but the highest bidder does not win. The platform ranks on your expected click-through rate multiplied by your bid and charges through a second-price auction, so you usually pay less than your maximum. That is why a strong listing makes your ads both cheaper and more effective than a higher bid.
Many sellers switch on a campaign, pick a budget and wait. The clicks come, but the sales do not, or the sales come but the ad costs eat up the whole margin. The conclusion is then often that advertising no longer works, or that more budget is needed, while the problem is somewhere else. To see where it really is, we go a few layers deeper than the average explanation: the auction, what you really pay, and the mistakes that burn your budget.
Why can you hardly do without advertising on bol anymore?
Because visibility is scarce and competition is fierce. There are more than 50 million items on bol, while around 13 million customers are searching. On mobile, where most visitors are, you often see only two results directly on screen for a search, and both are ads. If you are not among them, you do not exist for most buyers.
A few years ago you could put a product online and it more or less sold itself. Those days are over. With organic findability alone, you will not make it as a new seller anymore.
Advertising is not a button you switch on, after which the sales roll in. In practice we see two groups that make it. The first is the group with a bigger starting budget that does it properly from day one: good photos, a well-thought-out listing, and enough budget to get through the learning phase. The second is the group that starts small, does not make a profit straight away, but uses every sale to learn and improve. The group in between, which puts a product online and hopes it does something, often disappears after a few months. Not because bol does not work, but because the system is not understood.
What exactly does advertising on bol do?
Advertising only raises your findability, nothing more. Whether people then click and buy depends on your listing, your price and your reviews. If you remember one thing from this whole piece, make it this: a product with a poor listing that gets more visibility will get more clicks, but no extra sales. More clicks without sales means more costs without results.
Advertising and the quality of your offer are therefore always linked. Buying visibility for a product that does not convince yet only makes the problem more expensive.
Which three ad placements does bol have?
Bol has three kinds of ad placements, and they differ in purchase intent. You see that difference reflected in the price per click.
- Keyword pages. Your ad appears at the top of the results when someone searches for, say, "blue yoga mat". This is the most expensive placement, because purchase intent is highest here. Someone searching for a specific product is often almost ready to buy.
- Category pages. Your ad sits among the products when someone browses through, say, "sports and fitness". The intent is less focused, the price per click lower, and the conversion usually lower too.
- Product pages. The ads under "also view" or on a competitor's page. You ride on the intent of someone who is already looking at a comparable product. Cheaper than keyword pages, and with the right competitors as a target it can work well.
Which placement works best differs per product and per category. Most sellers start with keyword pages because of the high intent, but do not leave the other two untouched. A product-page ad might well turn out to be the most profitable placement for your product.
How does bol decide who comes out on top?
Bol does not let the highest bidder win, but ranks on your expected click-through rate multiplied by your bid. The platform looks at three things at once. First relevance: does your product match the search query? If not, you are not in the running at all. Then your expected click-through rate: how likely is it that someone clicks on your product? And finally your bid: how much you are willing to pay per click. The last two are multiplied, and bol sorts on the result (the expected revenue per impression).
The reason the click-through rate counts so heavily is simple: bol only earns money when someone clicks, not on an impression. A product that gets clicked more often is therefore worth more to bol.
An example makes it concrete. Two sellers advertise on the same keyword. Seller A bids 1 euro per click and has an expected click-through rate of 2 percent. Seller B bids 70 cents, but has an expected click-through rate of 4 percent. Seller A comes out at 2 percent times 1 euro, which is 2 cents of expected revenue per impression. Seller B comes out at 4 percent times 70 cents, which is 2.8 cents. Seller B wins, despite the lower bid, because bol expects to earn more from him per impression. So it is not about who has the deepest pockets.
What is a second-price auction, and what do you really pay?
Your bid is a ceiling, not a fixed amount. In a second-price auction you do not pay your full bid, but just enough to beat the seller below you, plus a small increment. If you bid 1 euro and the seller below you bids 80 cents, you pay slightly more than 80 cents, not your full euro.
That means aggressive bidding does not automatically cost a lot more. What you really pay per click depends on what your competitors do. Bol shows you an average winning bid: the average of what winning ads pay for a placement. That is a good indication, not a guarantee. If you have a product with a low click-through rate, you often pay more than that average for the same position. If your product converts well, you often pay less.
What determines your expected click-through rate?
Everything the consumer sees before the click: your main image, your title, your price and your reviews. Of those elements, your main image has by far the biggest impact. A white background is mandatory on bol, so you do not need to get creative there, but there is plenty of room to stand out within those rules. If your competitors align their product to the left, align yours to the right. If one or two colours dominate your category, pick a contrasting colour. If everyone photographs the product straight on, a slightly tilted photo already draws extra attention. The goal is not to be extremely different, because that looks unprofessional, but to stand out subtly, so the scrolling consumer's eye lingers on your photo.
There is a double effect here, and that is why your listing matters more than your bid. A higher click-through rate directly delivers more clicks. But because bol earns per click, the system also rewards a higher click-through rate with a lower price per click: at the same bid you get a better position, or at the same position you pay less. Suppose you change your main image and your click-through rate rises from 1 to 1.5 percent. That sounds small, but it is 50 percent more clicks for the same number of impressions, and on top of that you pay less per click.
Optimising your listing costs nothing extra per click and delivers more at a lower price; raising your bid does not. If you want to switch on your ads tomorrow, first look at your listing and especially your main image.
What needs to be right before you spend a single euro on ads?
Your listing. Advertising with a poor listing means more clicks that do not convert, and so higher costs with nothing to show for them. You are then paying bol to send people to your product who then drop off. Go through these points before you start:
- Title. Clear, with the most important features, and readable on a small screen. Most visitors order via mobile.
- Main image. The first thing someone sees in the results. If it does not stand out, nobody clicks, and then your bid does not even matter.
- Description and specifications. Fill them in completely. The consumer may not read them, but bol uses them to match your product to search queries. If someone searches for "sports bag red" and you have not filled in the colour attribute, you miss that match, and a competitor with fewer sales who did fill it in can rank above you.
- Price. Realistic compared to the rest, but not necessarily the lowest. A tip: put a new product online well before launch at a slightly higher price and lower it as soon as your stock arrives. A promotion label then appears automatically, which helps your click-through rate and your conversion.
- Reviews. The first ones make the difference. The gap between zero reviews and a few reviews is big; after that it levels off.
- Delivery time. If you offer ordered-today-delivered-tomorrow, you stand stronger in the auction than someone who takes three days. If you use logistics via bol, that alone strengthens your position.
- Stock. If you structurally run out of stock or your stock is very low, your ads perform worse. Bol does not want customers clicking on an ad for a product that will not be available for another week.
Why is profitable advertising from day one not realistic?
Because a new product without reviews converts structurally below average. Customers simply trust a product with reviews more, and there is no getting around that. Advertising in the early phase is therefore an investment, comparable to the marketing budget of your own webshop.
That investment pays itself back through a flywheel. You buy visibility with ads, you bring in sales, you build relevance (which is mainly about sales numbers, not revenue), and once you are visible enough organically, you can scale your ads back. A sale counts towards your relevance straight away; a review often takes a few weeks to be posted, and it is precisely those reviews that determine whether your future sales rise. For most products you are looking at three to six months of active advertising before your organic positions start to rise seriously, depending on your category and how quickly reviews come in. That is a guideline, not a hard limit.
We have worked out that flywheel separately in why a new product on bol starts at the bottom. The core here: that investment only works if your foundation is right.
ACOS and TACOS: which one should you really track on bol?
ACOS shows what you spend on ads relative to your ad revenue, but says nothing about your profit. TACOS does that better, because it sets your ad costs against your total revenue, including organic.
ACOS stands for Advertising Cost of Sales: the percentage of your ad revenue that you spent on ads. If you spend 100 euros and sell 1,000 euros' worth through ads, your ACOS is 10 percent. That sounds low, but it says nothing about what you keep. If your margin after all costs is 15 percent, an ACOS of 10 percent already eats up two thirds of your margin. At an ACOS of 15 percent you break even on those sales, and above that you earn nothing anymore. Many sellers think they are doing well on their ACOS, while they are hovering around break-even or even making a loss, because they have never worked out their real margin. Which costs belong in that margin is covered in profitability on bol.
TACOS stands for Total Advertising Cost of Sales: your ad costs divided by your total revenue, so including your organic sales. That metric is often more valuable. If your TACOS drops while your ad budget stays the same, your organic sales are rising, and that is ultimately what you want to see. ACOS can fool you, TACOS cannot. Build up that metric once you are a few months in; it is your real indicator of whether your investment is paying itself back.
What is cannibalisation, and how do you prevent it?
Cannibalisation is paying for sales you would have made without the ad anyway. That easily costs sellers a few hundred euros a month without them noticing. If your product already ranks high in the organic results and someone still clicks on your ad above it, you pay for a click you would have had for free: that customer would probably have scrolled on to your organic spot.
This mainly plays a role with products that already sell well and with brand-name or very specific product keywords. If someone searches for your brand name, they are already convinced, and advertising adds little. Yet it does have a function: if you do not advertise on your own brand name, a competitor can, and put their product above yours. Stopping completely is therefore not a solution.
What is smart: look at the added value at product level. How many extra sales does that ad deliver compared to none? That is hard to measure, but you estimate it by switching off the ad on a product that already sells well for a week and watching what your total sales do. If they barely drop, that ad was mostly cannibalisation. To judge that, you want to be able to see your organic position separately from your sponsored position; why that difference matters is explained in rankings on bol: organic versus combined. A second leak is keywords that do get clicks but deliver no sales. Go through your keywords at least once a month and switch off what does not convert.
Which three mistakes cost sellers the most?
Too little patience in the learning phase, putting everything on one keyword, and not distinguishing between launch budget and optimisation budget. At MarktMentor we look at the ad data of hundreds of sellers every week, and these three keep coming back.
- Too little patience. A new campaign needs time to learn what works. Many sellers see a high ACOS in the first week and switch everything off, or push the bids so low that the ads are no longer shown at all. Give the system at least two to four weeks to collect data before you make big changes.
- Everything on one keyword. Sellers find their winning keyword and pour their whole budget into it. That works in the short term, but as soon as the price on that keyword rises or a competitor bids harder, you grind to a halt. Build a mix: a few keywords with high purchase intent for sales, and a few broader, cheaper keywords that attract traffic. How to find them is covered in finding relevant keywords for your bol campaign.
- No distinction between launching and optimising. A freshly launched product has high ad costs and low conversion. That is normal, you have to get through it. But a product that has been running for a year and still spends 30 percent of its revenue on ads is no longer in the launch phase. Then the listing no longer works, or the product is structurally too weak to run organically. Ask yourself every three months which products are in which phase, and adjust your strategy accordingly.
The common thread: advertising is woven into your whole store
For a new product, advertising on bol is hardly a choice anymore, but it is also not a matter of spending money and hoping for the best. The system does not reward the highest bidder, but the product the consumer most often wants to click, combined with what you are willing to pay. A better listing therefore makes your ads both more effective and cheaper. The early phase is an investment: you build relevance through ads so that later you become less dependent on them. That only works if your foundation is right, meaning your photos, your title, your price and your description.
In short:
- Advertising only raises your findability. If your product, listing or price is not right, more visibility makes the problem more expensive.
- Bol ranks on expected click-through rate multiplied by bid and charges through a second-price auction. Your listing therefore weighs more than your bid.
- Track TACOS alongside ACOS: TACOS shows whether your organic sales are really growing.
- Factor in cannibalisation and switch off non-converting keywords monthly.
- Give a campaign two to four weeks to learn, and assess every three months which phase each product is in.
Setting up campaigns, choosing the right keywords, determining your bids and knowing when to scale up or down is a discipline in itself. That is why at MarktMentor we are building an advertising platform that handles the campaign structure and the daily optimisation for you. If you want to see how that works, start a free trial and try it yourself.
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