If your rankings dropped in the last week of March and you didn’t change anything on your site, Google’s March 2026 core update is the most likely reason. Core Web Vitals now carry significantly more ranking weight, and SEMrush Sensor data showed over 55% of tracked domains shifting more than five positions during the rollout.
Here’s how to check if you’ve been hit and what to fix first.
Content Overview
What changed in the March 2026 update
Google increased the ranking influence of Core Web Vitals. That’s the set of three metrics Google uses to measure how your site performs for real users on real devices.
The three metrics are:
LCP (Largest Contentful Paint) measures how long it takes for the main content on your page to load. Think: the hero image, the headline, the first thing a visitor sees. Google considers under 2.5 seconds “good.”
INP (Interaction to Next Paint) measures how quickly your site responds when someone interacts with it. Clicking a button, tapping a link, or typing into a form all count. Under 200 milliseconds is “good.”
This metric replaced the older FID (First Input Delay) in March 2024. The March 2026 update gave it significantly more ranking weight than it previously carried.
CLS (Cumulative Layout Shift) measures how much the page jumps around while it loads. You know the experience: you go to tap a button and the page shifts, so you hit an ad instead. Under 0.1 is “good.”
None of these metrics are new. What’s new is how heavily Google weighs them when deciding where your pages rank. Sites that were borderline before, sitting in the “needs improvement” range, are now feeling the impact in their organic positions.
How to check your scores in under 10 minutes
Two free tools will tell you most of what you need to know.
Step 1: PageSpeed Insights
Go to pagespeed.web.dev and enter your homepage URL. Then test your top 3-4 landing pages individually. Each page gets its own score.
When the results load, look at the section labelled “Discover what your real users are experiencing.” This is your field data, based on actual visitors to your site over the past 28 days.
It matters more than the lab data below it, because lab data simulates a test environment. Field data shows what’s happening for your customers on their connections.
You want green on all three Core Web Vitals. Amber or red on LCP or INP is likely contributing to any ranking movement you’ve noticed since late March.
Step 2: Google Search Console
Log into Search Console and open the Core Web Vitals report. You’ll find it under “Experience” in the left menu. This shows your entire site’s performance, grouped by URL pattern.
Search Console splits results into “Good,” “Needs improvement,” and “Poor.” Focus on the “Poor” URLs first. These are the pages Google is most likely to deprioritise in rankings.
Step 3: Check the trend
The Core Web Vitals report in Search Console also shows a timeline. If your “Poor” count jumped in late March without any changes on your end, it’s not a coincidence. The update’s increased weighting is the most likely cause.
What INP measures and why it matters now
LCP and CLS have been around longer and are more intuitive to understand. INP is different because it measures interactivity, not just loading.
INP tracks what happens when a visitor taps your navigation menu or clicks “Add to Cart.” It measures the gap between their action and the browser’s visual response.
A 400-millisecond delay on a button click feels sluggish. The visitor might not consciously register it, but they’re more likely to abandon the form or navigate away.
Poor INP scores typically come from heavy JavaScript execution, third-party scripts, and unoptimised event handlers. Chat widgets, analytics tags, heatmap tools, and remarketing pixels all compete for the browser’s attention. Every user interaction triggers all of them at once.
Picture a site running Google Analytics, a Facebook Pixel, Hotjar, a live chat widget, and a cookie consent banner. That’s five separate scripts the browser must process before it can respond to a click.
Each one adds milliseconds, and they compound.
What to fix first: the 90-day priority list
If dev time is tight, prioritise in this order.
Weeks 1-2: Quick wins
Images are almost always the first thing to address. Uncompressed images are the single most common reason for poor LCP scores on Australian SME websites. Convert to WebP or AVIF formats and compress to appropriate file sizes.
Make sure you’re serving correctly sized images for each device. A 4000px wide hero image served to a mobile screen is wasting bandwidth and time.
Custom fonts can also slow your LCP. If your site uses them, set font-display: swap so text renders immediately with a fallback font. The custom font loads in the background without blocking the page.
Remove any CSS or JavaScript files that aren’t being used on the page. WordPress sites accumulate these over time as plugins are added and removed. Caching plugins like WP Rocket and similar performance tools can help identify and defer unused assets.
Weeks 3-6: Medium impact
Audit every third-party script on your site. Open your browser’s developer tools, go to the Network tab, and reload the page.
Count the requests from external domains. Each one is a potential INP problem.
Is that live chat widget generating leads? Or is it costing you 150 milliseconds of interaction delay for nothing? Has anyone on your team logged into the heatmap tool in the past six months?
Lazy loading for below-the-fold images and embeds can also make a meaningful difference. If a YouTube embed or Google Map sits halfway down the page, load it only when the visitor scrolls there.
Server-side caching solutions like Varnish can reduce server response times and improve LCP scores. This is especially useful on sites with more complex infrastructure.
Weeks 7-12: Structural fixes
If your quick wins and script audit haven’t brought your scores into the green, the remaining issues are typically structural. JavaScript execution time, server response time (TTFB), and hosting infrastructure are the usual suspects.
These fixes usually require developer involvement. The key question for your developer is: “Which long tasks are blocking the main thread during user interaction?”
Chrome DevTools’ Performance panel shows this clearly. Tasks longer than 50 milliseconds are flagged as “long tasks” and are the primary cause of poor INP.
If your TTFB (Time to First Byte) is above 600 milliseconds, your hosting environment may be the bottleneck. No amount of front-end optimisation will compensate for a slow server.
Core Web Vitals could be making your Google Ads more expensive too.
Core Web Vitals feed into your Google Ads landing page experience score. That score is one of the three components of Quality Score and a lower Quality Score means you pay more per click for the same ad position.
If your landing page experience drops from “above average” to “average” or “below average,” your Quality Score drops. Google then charges a higher CPC to maintain the same position. Or your ad drops to a lower position at the same cost.
A slow website is now costing you twice: once in organic rankings and once in paid advertising efficiency. Fixing site speed improves both channels simultaneously.
Running technical SEO and Google Ads under the same roof catches these problems early. An SEO team that doesn’t talk to the web team leaves money on the table. So does a paid team unaware of a site speed problem.
The traps to avoid
Don’t chase a perfect score. PageSpeed Insights shows a number out of 100. That number is a lab-based estimate and is less important than your field data.
A site scoring 65 in the lab but green on all three field metrics is in a stronger position. A site scoring 90 with red field data is not.
Don’t strip functionality to improve speed. The goal is a fast and functional site.
Removing your contact form or disabling your image gallery to hit a better score defeats the purpose. Optimise the assets, don’t remove the features.
Don’t treat this as a one-off project. Every new plugin, tracking script, or design change can affect your Core Web Vitals. Build a monthly check into your workflow.
Five minutes in PageSpeed Insights once a month catches problems before they become ranking problems.
Don’t assume your developer already knows about these changes. The March 2026 update’s increased CWV weighting is an SEO development.
Your developer builds sites. They may not be tracking Google’s ranking algorithm changes.
What to do this week
Run PageSpeed Insights on your top five landing pages. Check your Core Web Vitals report in Search Console. Amber or red on INP or LCP is very likely contributing to any ranking drops you’ve noticed since late March.
If your scores are green across the board, you’re in a strong position. The sites around you may not be, and that’s an advantage worth holding onto.
If you’re seeing problems and want help diagnosing the full picture, talk to our web team. You can also get in touch with our SEO specialists. We run both under one roof for exactly this reason.
