You open the device report and the answer looks obvious. Phones are eating most of the budget, and a lead from a phone costs nearly twice what a lead from a desktop costs. So you do the sensible thing. You find the bid adjustment column, set mobile to minus 30%, save it, and wait for the cost per lead to come down.
It doesn't. A month later the split looks about the same, and nothing in the account tells you why. There is no warning next to the setting and no error message. The number you typed is sitting right there in the column, exactly where you left it.
Here is why. If your campaign uses one of Google's Smart Bidding strategies, and most campaigns do now, Google is not using that number. It has not been using it for years. It kept the column. It stopped reading it.
The Bid Adjustment Box Is Still There. Smart Bidding Stopped Reading It.
A bid adjustment was built for a world where you set the bid yourself. You told Google "pay up to $4 a click," and then you added rules on top: 20% more on Saturdays, 30% less on tablets, 15% more in the zip codes that buy. Google multiplied your bid by those percentages in every auction. That system was called manual bidding, and for a long time it was the only system.
Smart Bidding replaced it. Instead of you setting a bid, you give Google a goal, and Google sets a fresh bid for every single search based on how likely that search is to turn into the result you asked for. When Google is setting the bid, your percentage has nothing to multiply.
Google's own help page on bid adjustments lays out what each strategy does with a device adjustment, and the answer is blunt:
- Target ROAS: only minus 100% works. Anything else is ignored.
- Maximize Conversions: only minus 100% works.
- Maximize Conversion Value: only minus 100% works.
- Target CPA: the adjustment changes your target for that device, not your bid. More on that in a minute, because it is the one that catches people out.
- Manual CPC and Maximize Clicks: the adjustment works the old way.
Google is just as direct in the sentence above that table: if you use Smart Bidding, you don't need to make manual bid adjustments, and if you make one, "it won't be supported." The same page says the identical thing about ad schedule adjustments. Smart Bidding respects the hours you set, but it ignores the plus 20% you put on Saturday mornings, which is why we argued in Your Phones Close at 6. Your Google Ads Keep Buying Calls Until Midnight. that the schedule itself is the setting that matters.
This is not a hidden trick or a recent change. It is how the system has worked since Smart Bidding took over, and it is the reason so many owners feel like they have no control. They are pulling a lever that isn't connected to anything anymore.
We checked our own client accounts while writing this. Across 31 accounts, four Smart Bidding campaigns were still carrying device adjustments Google doesn't use, left over from earlier setups. If it happens in accounts we watch every week, it is almost certainly sitting in yours.
Target CPA Is the Exception. It Moves Your Goal, Not Your Bid.
Target CPA is the one Smart Bidding strategy where a device adjustment still does something. It just does something different from what the column suggests.
Under Target CPA, you tell Google what you're willing to pay for a lead, say $100. Google then bids, search by search, to bring you leads at about that cost. A device adjustment here doesn't touch the bid. It changes the target for that device.
Google's help page gives its own example: with a $10 Target CPA, a plus 40% adjustment on mobile raises your target to $14 for mobile searches. Run that the other way and a minus 30% adjustment on mobile tells Google you'll pay $70 for a phone lead instead of $100.
That sounds like the control you wanted, and sometimes it is. But notice what you actually asked for. You didn't say "spend less on phones." You said "only buy phone leads that come in under $70." If Google can't find many of those, it will simply buy fewer phone leads, and since phones usually carry most of the searches, your total lead count can drop with them. A modest-looking adjustment can quietly shrink the whole campaign.
So treat a device adjustment on Target CPA the way you'd treat changing the target itself, because that is exactly what it is. A target is an instruction Google follows literally, which we unpacked in Your Google Ads Bid Target Isn't a Wish. It's an Instruction. Use it deliberately, when you know a phone lead is genuinely worth less to your business than a desktop lead, and know the number you're aiming at. Don't use it as a nudge.
This is the more common case in practice. In our own review, nine of the thirteen campaigns carrying a device adjustment ran Target CPA, each one quietly setting a different target for phones or desktops that nobody had looked at in months. If you have a Target CPA campaign, check for this first.
Smart Bidding Already Prices Every Phone Search
The reason Google ignores your percentage isn't arrogance. It is that Smart Bidding is already doing a more detailed version of the same thing.
Google lists device as one of the signals Smart Bidding uses at what it calls auction time, the split second before each ad is shown. Alongside device, it weighs the searcher's location down to the city, the time of day and day of the week, the exact words they typed, and a long list of other signals only Smart Bidding can see. It combines them, so it isn't bidding on "mobile," it's bidding on "a phone in this suburb at 7 p.m. on a Tuesday typing this exact phrase."
A flat minus 30% on mobile is a blunt instrument by comparison. It treats the person searching "emergency plumber near me" from their kitchen at 10 p.m. the same as the person idly browsing water heaters on their phone during lunch. Smart Bidding can tell those two apart. Your percentage can't.
That doesn't mean Smart Bidding always gets it right. It only knows what you tell it, and that is where most device problems actually come from.
The Device Report Is Not a Scoreboard
The device report is where most bad device decisions start, because it looks like a scoreboard and it isn't one. It shows you where conversions were recorded. It doesn't tell you what those conversions were worth, or why they landed on that device.
Here is what it looks like in practice, across three kinds of accounts we manage.
Local service businesses that get calls. A chiropractic clinic: phones brought in 90% of its conversions over the last 90 days, at $140 each against $225 on desktop. A pain clinic: $59 on mobile against $130 on desktop. A therapy practice: $85 against $213. Easy verdict, phones win. But in all three, most of the conversions were phone calls, and phone calls happen on phones. The report isn't telling you mobile searchers are better customers. It's telling you that you count calls, and calls come from the device with a dial button.
An online store. Over the past year, its main Performance Max campaign spent almost exactly the same on desktop and mobile, about $33,500 each. Mobile brought in 604 orders and desktop brought in 345, so on cost per order, mobile looks like the clear winner at $56 against $97. Now look at revenue. Desktop orders averaged about $308. Mobile orders averaged about $125. Per dollar spent, desktop returned about 3.2 times its cost and mobile about 2.2 times. Judged on order count, you'd cut desktop. Judged on revenue, you'd cut mobile. Both readings come from the same report.
A business where desktop really does win. A vending business selling to other businesses: over the past year, desktop converted 5.7% of its clicks into leads at $274 each, and mobile converted 1.6% at $558. Calls were split evenly between the two, so this one isn't a call-counting quirk. The buyer researches at a desk. That campaign carries a minus 50% mobile adjustment. It runs Maximize Conversions with no target, so Google doesn't use it, and anyone reading the settings would assume phones are being held back when they aren't.
Two rules come out of this. First, before you judge a device, split its conversions by type. If calls dominate, mobile will always look best, and that tells you about your conversion setup, not your customers. Second, if your sales vary in size, give Google the values. A store on Maximize Conversion Value or Target ROAS, with real order values flowing in, lets Smart Bidding see that a desktop order is worth more than double a phone order and bid for that, which no percentage in a column could do.
Switching a Device Off Is the Only Lever Smart Bidding Still Obeys
Minus 100% is the one device setting every Smart Bidding strategy still respects. It isn't really a bid adjustment. It's an off switch: no ads on that device, at all.
There are honest reasons to flip it. A locksmith or a towing company may decide desktop searches almost never turn into jobs, because nobody locked out of their car is sitting at a desk, and a few agencies run those businesses on phones only. A software company selling a product that only works on a computer might reasonably exclude phones. A campaign built around call-only ads has no use for desktop at all.
But it costs more than it looks like. When you exclude a device, Google stops learning from it entirely, and the conversions that used to come from it stop feeding your bidding. Many purchases also cross devices, with someone searching on a phone at lunch and buying on a laptop that evening. Cut the phone and you may be cutting the first half of the desktop sale. Before you switch a device off, check whether it has truly failed over a long stretch, at least 90 days and ideally longer, and with its conversions split by type, not a single bad month.
If a device isn't worth zero, it isn't a candidate for minus 100%. Leave it to the bidding.
A Separate Mobile Campaign Splits Your Data in Half
There is a popular workaround: if Google won't let you price devices inside one campaign, build two. One campaign for phones, one for desktop, each with the other device excluded, each with its own budget.
It works, mechanically. It also cuts your conversion data in half. Smart Bidding learns from the conversions inside each campaign, and two campaigns with 15 conversions a month each are two weaker students than one campaign with 30. We wrote a whole piece on that trade-off: You Organized Your Google Ads Account. You Starved It.
Device campaigns earn their place in a few situations: when the two devices really need different ads (call-only ads on phones, for example), different landing pages, or genuinely different budgets because they serve different businesses. For a small account, those cases are rare. If the only reason is "I want to bid less on phones," the split usually costs more in learning than it saves in clicks.
Performance Max Lets You Pick Devices. It Doesn't Let You Price Them.
Performance Max has always been the campaign type with the fewest controls, and device targeting was one of the things owners kept asking for. Google added it. In a Performance Max campaign's settings, you can now choose which devices to show on: computers, phones, tablets and TV screens.
What you can't do is set a percentage. In Google's own eligibility chart, Performance Max has no device bid adjustment at all. It's in or out. That makes it the same decision as minus 100% on Search, with the same costs. Most of the time the right move is to leave all devices on, give the campaign accurate conversion values, and let it sort out the bidding. Turn a device off only when the business case is as clear as the locksmith's.
A Mobile Page That Doesn't Convert Is Not a Bidding Problem
When a device really does underperform, and the conversion mix doesn't explain it, the bid is rarely the cause. The page usually is.
Pull up your landing page on a phone and try to do what a customer would. Does it load quickly on a cellular connection? Is the phone number a button you can tap, or plain text you have to copy? Does the form fit on the screen, or does it ask for eight fields with a thumb? Is the offer visible without scrolling past a giant photo? We covered this in detail in Your Site Looks Great on Your Laptop. Your Customers Are on Their Phones.
Fixing any of those does what the bid adjustment was supposed to do, only it works. A page that converts phones better makes every phone click cheaper per lead, and Smart Bidding responds to that on its own by buying more of them.
Ten Minutes in Your Google Ads Account Will Show Which Settings Are Dead
Here is the check, start to finish.
- Find your bid strategy. In the campaigns list, add the bid strategy type column. Note which campaigns use Target CPA, Target ROAS, Maximize Conversions or Maximize Conversion Value, and which, if any, still use manual CPC.
- Find the leftover adjustments. Open each campaign, go to the devices report, and look at the bid adjustment column. On Target ROAS, Maximize Conversions or Maximize Conversion Value, anything other than blank or minus 100% is doing nothing. Remove it so the account stops misleading the next person who reads it.
- Check Target CPA campaigns separately. Any device adjustment there is a different target for that device. Do the arithmetic, and decide if that's a target you actually want. If not, remove it.
- Read the device report by conversion type. Segment conversions by type and by device before you judge either one. If calls make up most of your conversions, expect mobile to look best.
- Pick the right lever. If order sizes or job sizes differ by device, send real values and use a value-based strategy. If a device has failed for 90 days or more on every measure, consider minus 100%. If phones underperform for no clear reason, fix the mobile page first.
None of that takes more than an afternoon, and most accounts will find at least one setting that has been sitting in the column doing nothing for a long time.
You Don't Have to Fight Smart Bidding. You Have to Feed It Better Data.
The instinct behind a device adjustment is a good one. You noticed that some customers are worth more than others, and you wanted your money to follow them. Smart Bidding wants the same thing. It just won't take the instruction as a percentage anymore. It takes it as accurate conversions, honest values, and a page that works on the device people are holding.
This is the kind of thing we sort out in accounts every week, usually in the first hour. If you'd rather have someone handle the Google Ads management side while you run the business, we'd be glad to help. And if you're here to learn it and do it yourself, you now know exactly where to look.
