What is mobile-first indexing?

Google crawls and indexes the mobile rendering of a page and uses it for ranking on all devices. Content that only exists in the desktop template is not considered.

Do I need a separate mobile site?

No. A responsive site with one URL per page is the recommended setup, because it keeps content, links and signals in one place instead of splitting them across two hostnames.

Is content inside an accordion penalised on mobile?

No, as long as it is present in the HTML and expandable. Collapsed content is indexed normally; content injected only after a user action or loaded conditionally may not be.

Which Core Web Vital should I fix first on mobile?

Largest Contentful Paint, and usually by compressing or resizing the hero image. Interaction to Next Paint comes next and is almost always about reducing JavaScript work.

How do I test mobile performance realistically?

Test with network throttling and a mid-range device profile rather than your own phone on Wi-Fi, and re-run after every deployment so regressions are caught while they are cheap to fix.

Mobile SEO: rank on the version Google actually indexes

Last reviewed and updated September 3, 2026

Mobile is the indexed version of your site and the majority of your traffic, so mobile problems are ranking problems. This guide covers indexing, content parity, layout, asset weight, Core Web Vitals and ongoing testing.

Each step links to the free browser tool that performs the check, so you can measure as you read.

1Understand mobile-first indexing

Google indexes the mobile rendering of your pages. Anything hidden, collapsed away entirely, or omitted from the small-screen template is effectively missing from the version that gets ranked.

Fetch the page as a crawler and read the markup rather than trusting the desktop view.

Tools for this step

These checks need a data provider connected. For a live measurement right now, run the SEO dashboard audit against the same URL.

Go deeper

Technical SEO guide — Crawling and indexing in dependency order.

2Keep content and links at parity

Headings, body copy, structured data and internal links must exist on mobile in full. Accordions are fine when the content is in the HTML; conditionally loading it only on desktop is not.

Check that the mobile navigation exposes the same internal links, since that is how deeper pages get discovered.

Tools for this step

Word CounterCount words, characters, sentences and paragraphs, estimate reading time and see the keyword frequency of any passage.Live

HTML Viewer & SanitizerPreview HTML with scripts, event handlers and unsafe URLs stripped, and inspect the cleaned markup.Live

Tools marked Live open a working workspace that runs entirely in your browser — start with Word Counter and HTML Viewer & Sanitizer.

3Fix layout, tap targets and readability

Text should be legible without zooming, tap targets should be comfortably separated, and nothing should overflow horizontally. These are usability issues that surface as bounces long before they surface as ranking changes.

Reserve space for images, ads and embeds so the layout does not jump while loading.

Tools for this step

CSS MinifierStrip comments and redundant whitespace from stylesheets.Live

HTML MinifierCollapse whitespace and comments from markup while keeping pre and textarea content intact.Live

Tools marked Live open a working workspace that runs entirely in your browser — start with CSS Minifier and HTML Minifier.

4Cut image and asset weight

Phones on mobile networks pay for every kilobyte. Compress, size correctly for the viewport, and lazy-load anything below the fold — the hero image alone usually decides your Largest Contentful Paint.

Convert oversized PNG photography to JPEG, and stop shipping desktop-resolution files to a 390px screen.

Tools for this step

Image CompressorRe-encode JPG, PNG or WebP files at a quality you choose and compare before/after file size.Live

Image ResizerResize images to exact pixel dimensions with optional aspect-ratio lock and instant preview.API

PNG to JPGFlatten PNG transparency onto a background colour and export a JPEG at your chosen quality.API

Crop ImageTrim an image to a rectangular selection using numeric crop controls and a live overlay.API

Tools marked Live open a working workspace that runs entirely in your browser — start with Image Compressor.

Go deeper

Image optimisation for page speed — Compression and sizing in the order that moves LCP.

5Chase Core Web Vitals on phone hardware

LCP, INP and CLS are collected from real visits, and most of those visits are mobile. Lab scores on a fast laptop hide the JavaScript cost that mid-range phones actually pay.

Trim blocking third-party scripts first: tag managers, chat widgets and font loaders are the usual offenders.

Tools for this step

HTML MinifierCollapse whitespace and comments from markup while keeping pre and textarea content intact.Live

CSS MinifierStrip comments and redundant whitespace from stylesheets.Live

Tools marked Live open a working workspace that runs entirely in your browser — start with HTML Minifier and CSS Minifier.

Go deeper

Core Web Vitals tools compared — Which measurement to trust for each metric.

6Test and monitor on real conditions

Throttle the connection, use a mid-range device profile, and re-test after every release. Mobile performance regresses silently whenever a new script is added.

Keep uptime, redirects and response time in the same routine — a slow redirect chain costs far more on mobile than on fibre.