The problem nobody audits
You launch a Google Ads or Meta Ads campaign. You check the targeting, the creative, the bids. But do you check that the landing page still exists?
According to CampaignTrackly, 25% of active ads point to dead pages: 404s, broken redirects or obsolete URLs. Every click on these ads is billed. Every visitor who lands on an error page leaves immediately. The budget is spent and nobody can convert.
Worse, most brands only audit their destination URLs once a quarter. Between two audits, pages die silently.
Why pages die
The causes are mundane and recurring:
1. Redesign or migration. A site redesign changes the URLs. The old pages become 404s. Nobody updates the ads.
2. Product removal. A product pulled from the catalog generates a 404 if no redirect is set up. The Shopping ad keeps pointing to nothing.
3. A typo in the final URL. A typo in the campaign's URL field. Google Ads doesn't check that the page returns a 200.
4. Expired landing pages. Promotional landing pages (sales, Black Friday) are deactivated after the event. Evergreen campaigns pointing to them keep running.
The real cost, month after month
The math is mechanical. Every click to a 404 is a paid click with zero chance of converting. Here's the impact based on the daily volume of clicks to dead pages:
| 404 clicks/day | CPC €0.50 | CPC €0.85 | CPC €1.20 | CPC €2.00 |
|---|---|---|---|---|
| 10 | €150/month | €255/month | €360/month | €600/month |
| 30 | €450/month | €765/month | €1,080/month | €1,800/month |
| 50 | €750/month | €1,275/month | €1,800/month | €3,000/month |
| 100 | €1,500/month | €2,550/month | €3,600/month | €6,000/month |
| 200 | €3,000/month | €5,100/month | €7,200/month | €12,000/month |
For a mid-market site with 200+ active campaigns and catalogs that change every week, 50 to 100 clicks/day on 404s is nothing unusual. That's €1,275 to €2,550/month of budget thrown away, before counting the indirect effects.
The collateral damage
Wasted budget is only the visible part. 404s in your paid campaigns cause three side effects:
Skewed attribution. The click is recorded, the session exists, but no conversion follows. Your campaign conversion rate drops. Your GA4 reports show an underperforming channel when the problem is the page, not the campaign.
Inflated bounce rate. A visitor who lands on a 404 bounces in under 3 seconds. That negative quality signal hurts your Quality Score on Google Ads, which raises your CPC on every ad in the group.
Confused Smart Bidding. Bidding algorithms see clicks with no conversions. They read this as a targeting problem and reallocate budget to less relevant audiences, so the damage keeps growing.
What standard tools miss
Google Ads checks the final URL only when the ad is created. If the page dies three months later, nothing alerts you.
GA4 records page views on 404s, but doesn't cross-reference them with the paid source. You have to build a custom report, know what to look for and check it regularly. In practice, nobody does.
SEO crawlers (Screaming Frog, Semrush) audit 404s but don't link them to ad spend. They flag a technical error and say nothing about the money lost.
How Korvus detects it
The principle is the same as for detecting sponsored out-of-stock products: Korvus cross-checks two signals in real time.
- The visitor comes from a paid campaign: identified by UTM, gclid or fbclid
- The page returns a state that can't convert: 404, empty page, server error, or out-of-stock product
When both conditions are met, Korvus triggers an alert with the euro amount already wasted. Whether it's a 404, an out-of-stock product or a page broken by a deployment, the result is the same: a paid click paid for nothing.
The action plan
Immediate audit. Export all the final URLs from your active campaigns. Test them with a crawler. Identify the 404s, redirect chains and slow pages.
Systematic redirects. Every deleted page needs a 301 redirect to the most relevant alternative. Never a bare 404 on a URL that receives paid traffic.
Continuous monitoring. A one-off audit isn't enough. Pages die every week. Monitoring that constantly cross-checks paid traffic against the state of landing pages is the only way to catch leaks before they pile up.
Key takeaways
- 25% of ads point to dead pages, according to market benchmarks
- Every click to a 404 is budget thrown away: from €255 to €5,100/month depending on volume and CPC
- 404s skew attribution, inflate the bounce rate and confuse Smart Bidding
- Standard tools (GA4, Google Ads, SEO crawlers) don't cross-reference page status with paid cost
- Detecting paid traffic + a page that can't convert in real time is the only way to stop the leak