Core Web Vitals Changed Again: INP Replaced FID, and Your Audit Process Probably Hasn't Caught Up

Google replaced FID with INP on 12 March 2024. WCAG 2.2 added 9 new criteria in October 2023. The European Accessibility Act became enforceable on 28 June 2025.

Modern web standards are evolving faster than ever—but most agency audit workflows are still running the same checks they ran in 2020.

The result: teams audit against outdated standards without realising it, shipping sites that pass 2020 requirements but fail current ones.

The March 2024 Core Web Vitals Update

Google announced officially that Interaction to Next Paint (INP) replaced First Input Delay (FID) as a Core Web Vitals metric on 12 March 2024.

This wasn't a minor adjustment. INP fundamentally changed how Google measures responsiveness:

FID (deprecated): Measured only the first interaction on a page INP (current): Measures all interactions throughout the entire page lifecycle

Google explains: "INP takes into account all interactions on the page and evaluates the entire cycle of interactions and the time until the next visual change on the page. This is more comprehensive than FID, which only measured the first interaction."

Current 2025 Core Web Vitals Thresholds

According to official Google documentation, these are the current thresholds your sites need to meet:

Largest Contentful Paint (LCP):

• Good: <2.5 seconds
• Poor: >4.0 seconds

Interaction to Next Paint (INP):

• Good: <200 milliseconds
• Poor: >500 milliseconds

Cumulative Layout Shift (CLS):

• Good: <0.1
• Poor: >0.25

Google's guidance: "A good INP score is less than 200 milliseconds, while an INP over 500 milliseconds is considered poor and may negatively impact your search rankings."

INP as a Ranking Factor

DebugBear confirms: "Interaction to Next Paint became one of the Core Web Vitals metrics in March 2024 and therefore is a Google ranking factor."

The competitive implications: "Since the INP score will be included in the calculation of this score, the INP score of your website will also become one of the determining factors affecting the ranking of your website compared to that of your competitors from March 12."

If your audit workflow is still checking FID, you're optimising for a deprecated metric that Google no longer uses for rankings.

The Business Impact of Poor Performance

Research from BrightVessel shows the business cost beyond rankings:

Sites with LCP >4 seconds see 61% lower conversions.

That's not a ranking penalty—that's direct revenue impact from users leaving before content loads.

John Mueller from Google provides important context: Core Web Vitals are "not worth over-focusing on tweaking scores just for SEO." They function as a tie-breaker between similar quality content, not a primary ranking driver.

But the conversion impact exists regardless of ranking effects. Performance matters for business outcomes beyond search visibility.

The Broader Standards Evolution Timeline

Core Web Vitals aren't the only standards that have evolved. Consider what's changed since 2020:

October 2023: WCAG 2.2 published

• Added 9 new success criteria vs WCAG 2.1
• Focus on mobile accessibility and cognitive disabilities
• Source: W3C Web Accessibility Initiative

March 2024: INP replaced FID in Core Web Vitals

• Changed from first-interaction to all-interactions measurement
• New threshold: <200ms good, >500ms poor
• Source: Google Developers

October 2024: UK WCAG 2.2 monitoring began

• WCAG 2.2 became enforceable UK legal standard
• Public sector monitoring active
• Source: GOV.UK Service Manual

June 2025: European Accessibility Act enforcement

• Affects UK businesses with EU customers
• Products/services must meet accessibility requirements
• Source: AbilityNet EAA Guidance

October 2025: Current date (one year WCAG 2.2 enforced, 19 months INP live)

The Audit Workflow Problem

Most agency audit workflows are static manual processes:

1. Team member remembers to check PageSpeed Insights
2. Looks at the scores
3. Maybe checks a few other tools
4. Makes note of issues
5. Moves on

The problem: which metrics are being checked?

If your workflow was established in 2020-2022, you're likely still checking:

• ❌ FID (deprecated March 2024)
• ❌ WCAG 2.1 (superseded October 2023)
• ❌ Outdated security header configurations

Current 2025 standards require:

• ✅ INP (not FID)
• ✅ WCAG 2.2 Level AA (not just 2.1)
• ✅ Current security headers (HSTS, CSP with frame-ancestors)
• ✅ Schema.org for AI search optimisation
• ✅ Modern framework patterns

The Business Cost of Outdated Audits

When your audit workflow checks outdated standards:

SEO impact: Sites optimised for deprecated FID instead of current INP Compliance risk: WCAG 2.1 audits miss 9 new WCAG 2.2 criteria Conversion loss: Sites with LCP >4s see 61% lower conversions Competitive disadvantage: Competitors checking current standards rank better False confidence: "We passed the audit" based on outdated requirements

What 2025 Comprehensive Audits Should Check

Performance (Core Web Vitals - 2024 Update):

• ✅ LCP (Largest Contentful Paint) <2.5s
• ✅ INP (Interaction to Next Paint) <200ms [Current since March 2024]
• ✅ CLS (Cumulative Layout Shift) <0.1
• ❌ FID (First Input Delay) [Deprecated March 2024]

Accessibility (WCAG 2.2 - October 2023):

• ✅ WCAG 2.2 Level AA (9 new criteria)
• ✅ Focus appearance (new 2.2 criterion)
• ✅ Target size (new 2.2 criterion)
• ✅ Dragging movements (new 2.2 criterion)
• ❌ WCAG 2.1 only [Superseded October 2023]

Security (Current Best Practices):

• ✅ HSTS (HTTP Strict Transport Security)
• ✅ CSP (Content Security Policy)
• ✅ CSP frame-ancestors directive (modern alternative to X-Frame-Options alone)

SEO (Modern Search):

• ✅ Schema.org markup for AI search
• ✅ Semantic HTML structure
• ✅ Mobile-first responsive design

GuardianScan: Auditing Against Current Standards

GuardianScan was built to solve the standards evolution problem.

The challenge: Web standards evolve continuously. Manual audit workflows remain static. Teams unknowingly audit against outdated requirements.

The solution: Automated checking against current 2025 standards, updated as standards evolve.

What GuardianScan checks:

• Core Web Vitals 2024: LCP, INP (not deprecated FID), CLS
• WCAG 2.2: All 9 new criteria included
• Modern security: HSTS, CSP, current header best practices
• AI search optimisation: Schema.org, semantic HTML
• Framework patterns: Modern JavaScript framework best practices

50 checks in 45 seconds across performance, security, accessibility, SEO, modern standards, and code quality.

The Future-Proof Approach

Standards will continue evolving. That's normal and expected as the web advances.

The question isn't "will standards change?"—it's "will your audit workflow keep up?"

Static manual workflows: Require retraining every time standards change Automated current checking: Updates automatically as standards evolve

When Core Web Vitals Matter (and When They Don't)

Let's be honest about where Core Web Vitals fit in the ranking picture:

Ranking factor reality:

• Core Web Vitals are a tie-breaker for similar quality content
• Not a primary ranking driver
• Relevance and content quality still outweigh performance

Business impact reality:

• 61% conversion drop with poor LCP (bigger impact than SEO)
• User experience affects business outcomes regardless of rankings
• Performance + relevance wins, not performance alone

Recommended approach:

• Meet "good" thresholds (<2.5s LCP, <200ms INP, <0.1 CLS)
• Focus on content quality and relevance
• Don't over-optimise scores at expense of user value
• Balance technical excellence with editorial excellence

The Modern Standards Checklist

Use this to verify your audit workflow checks current requirements:

Performance:

• LCP <2.5 seconds
• INP <200 milliseconds (not FID)
• CLS <0.1

Accessibility:

• WCAG 2.2 Level AA (including 9 new criteria)
• Focus appearance (2.4.11)
• Target size (2.5.8)
• Dragging movements (2.5.7)

Security:

• HSTS header configured
• Content Security Policy implemented
• frame-ancestors directive (modern clickjacking protection)

SEO:

• Schema.org markup for rich results
• Semantic HTML structure
• Mobile-responsive design
• Core content accessible to crawlers

Modern Standards:

• Responsive images (srcset, picture element)
• Modern image formats (WebP, AVIF)
• Lazy loading where appropriate
• Accessible interactive components

Honest Scope

GuardianScan checks current standards as of 2025. Standards will continue evolving—that's expected as web technology advances.

The value proposition: an audit tool that updates with standards, so you're always checking current requirements, not 2020 baselines.

No tool replaces understanding web standards evolution. Professional judgement about when to prioritise optimisation remains essential.

The Standards Evolution Continues

Web standards will keep evolving. Google will update Core Web Vitals again. WCAG will publish 2.3 eventually. Security best practices will advance.

The question: will your audit workflow evolve with them, or will you unknowingly optimise for deprecated standards?

Try GuardianScan free — Check INP, not deprecated FID. WCAG 2.2, not superseded 2.1. Current standards, not 2020 requirements.

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Standards Evolution Timeline

Core Web Vitals: Current vs Deprecated

Resources

• Google Developers: Introducing INP to Core Web Vitals
• Google Developers: Understanding Core Web Vitals and Google Search Results
• DebugBear: Measure and Optimise Interaction to Next Paint (INP)
• GOV.UK Service Manual: Understanding WCAG 2.2
• BrightVessel: Core Web Vitals in 2025

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Modern web standards deserve modern audit tools. Check current requirements, not 2020 baselines.