Back in September 2015, my post titled “Forty SEO Checklist Items for Agile Teams” laid out two well-structured lists: one for on-page optimization (things you do to each page) and the other for on-site optimization (site-wide technical, architecture, crawl, redirect management).

It remains a very solid reference because it covers the fundamentals: readable URLs, proper title tags, meta descriptions, canonical tags, H1 structure, sitemaps, robots files, broken link checks, site performance, mobile usability, etc.

If you’re working on individual pages or entire sites, you can use those checklists almost directly as success criteria for each release. The emphasis on clean code, valid HTML, accessibility, site speed, etc. still matter.

But while the fundamentals are still very much relevant, the SEO landscape has continued to shift — especially as we move beyond the site boundaries into the off-site ecosystem, and when you factor in AI, social media, virtual assistants, etc.

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What’s changed (and why we need to extend the list)

Here are some of the major shifts worth noting:

1. Off-site / external credibility really matters

In the original 2015 checklist the “on-site” section does include social sharing links, sitemaps, analytics, etc. But many of the external signals we now recognize were weighted differently.
Today, building trust, authority, and relevance outside your immediate site is a key component of SEO. That means things like:

• Backlinks from trusted media / editorial sources (not just random directories/blog comments)
• Brand mentions (even unlinked) from credible places
• Reviews, ratings on third-party platforms (for local businesses especially)
• Social media presence that drives engagement and signals relevance
• Guest posts, podcasts, videos, etc that place your brand/content in other credible ecosystems

For example, one article notes that while backlinks remain a core part of SEO, “traditional link building … has been ineffective for some time. Success requires creative ideas and real-world events that garner high-tier editorial coverage.” – Search Engine Land
Another states – “Off-page SEO is evolving beyond backlinks, and AI now recognizes brand mentions and authority signals.” – SGD

2. AI / Generative Search Engines are altering the game

Search is not just about keyword matching and links anymore. With large-language models, generative systems, and more sophisticated technology, content intent, reputation and entity-relationships are becoming more significant.
For instance – the concept of “Answer Engine Optimization (AEO)” and “Generative Engine Optimization (GEO)” is emerging to capture how AI-powered retrieval works rather than classic ranked lists. – Wikipedia
Similarly – “AI does not just count backlinks, it understands context, sentiment, and reputation.” – SGD

That means your content, your brand, your mentions, your cited authority all contribute to how well you appear (or are referenced) in AI-driven search results.

3. Social, review & multi-format content amplify signals

While share buttons and social icons were already present in the 2015 list (e.g., “Social Sharing – Make sure they are all set up and working properly” in the On-Site checklist) — the emphasis now is much stronger.
Social media accounts that are active (updated weekly or regularly), audience-relevant, engaging with comments/followers, provide additional signals of relevance → help drive both traffic and credibility.
For local and service-businesses, reviews (on Yelp, Nextdoor, Google Business Profile etc) are increasingly important for “trustworthiness” and therefore SEO strength.
Also, the proliferation of guest blog posts, podcast appearances, video placements, rich content off your site help broaden the footprint of your brand and content — thereby contributing to inbound traffic, authority, brand-mentions and trust.

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Building a holistic, modern SEO strategy

Putting this together, here’s how you can approach an updated, holistic SEO strategy combining the old and new.

Step 1: On-Page Optimization Layer

• Use my 2015 checklist as your foundation: human-readable URLs, short titles, unique meta descriptions, proper heading structure, canonical tags, alt-text for images, technical health (sitemap, robots.txt, redirects, site speed, mobile usability). – Pixelated Blog
• Make sure your content is high-quality (more than 250 words, relevant, avoiding thin/duplicate content). – Pixelated Blog

Step 2: On-Site Optimization Layer

• Continue with the 2015 checklist to ensure your site is technically healthy (404s fixed, server logs checked, performance optimized: compress images, minify CSS/JS) – Pixelated Blog
• Make sure analytics/webmaster tools are set up, review crawl errors, mobile usability, redirect chains etc. – Pixelated Blog

Step 3: Off-site & external credibility (the “authority & trust” layer)

Here’s how to build that layer in the AI + social era:

• Backlinks & media mentions: Seek editorial coverage from trusted external sites (news, industry publications, authoritative blogs). But more importantly now: relevance matters. Links from domain-relevant, trusted sources matter far more than many low-quality links. – rvsmedia.com
• Brand mentions & citations: Even unlinked brand mentions contribute to entity recognition and trust signals for AI-driven search. Monitor your brand’s mentions across the web and aim to increase meaningful citations. – SGD
• Social media activity: Maintain active social accounts with regular updates (weekly or more frequently), relevant to your audience, encouraging engagement (comments, shares, followers). The more your social presence is authentic and engaged, the stronger your brand footprint.
• Reviews & third-party platforms: For businesses especially in local/service categories, ensure you have consistent listing and good reviews on platforms such as Google Business Profile, Yelp, Nextdoor, and other industry-specific directories. Reviews help with trustworthiness signals.
• Guest content / rich formats: Appear as a guest blogger, podcast guest, video interview, or host your own webinar and repurpose/republish externally. These placements do double-duty: they bring referral traffic and build external credibility.
• Content that earns links/mentions: Create high-value content (original research, data, benchmarks, interactive tools, explainer guides) that others want to reference, share or link to. As one recent article flagged: “The future of link building lies in being referenced by authoritative sources across the web.” – Sure Oak

Step 4: Integrate and monitor across all layers

• Ensure your off-site and on-site efforts are aligned: content you publish on your site should easily lend itself to being referenced externally (so your site is the “home base”).
• Track key metrics: referring domains, domain authority/trust scores, brand-mention volume, social metrics (followers, engagement rate), review ratings/volume, unlinked mentions turned into links.
• Use tools to audit backlink health, brand mentions, potential toxic links. For example one guide notes: “Without measurement, strategies lack accountability.” – silicongraphics.ae
• Keep up with AI/algorithm shifts: as AI-powered search and generative results evolve, focus on entity recognition, thematic relevance, semantic relationships (not just keyword-density) and content that answers user needs.
• Think long-term: Off-site authority and trust don’t happen overnight. It’s more like a brand-building/PR plus SEO hybrid. The days of “quick link-spike → ranking boost” are largely behind us. – SGD

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Why this holistic mix matters

When you combine the strong on-page/technical foundation (so your site is crawlable, performant, relevant) and the external credibility/trust signals (media mentions, brand footprint, reviews, guest content, social engagement), you end up with a site and brand that search engines — including AI-driven ones — are more likely to trust, surface and recommend.

In short:

• On-site keeps you in the game (crawlable, relevant, technically sound)
• Off-site builds the reputation that makes you competitive
• AI & social layers amplify the effect by interpreting broader signals of trust/authority

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In summary

The checklist published in 2015 remains an excellent resource for on-page and on-site SEO. But in today’s era of AI, social media, brand ecosystems and rich content formats, you’ll want to extend your strategy with off-site and external signals: backlinks from trusted media, active social presence, guest appearances, reviews on major platforms, brand mentions and content designed to be referenced.

The goal: build a holistic SEO strategy that isn’t just about being found — it’s about being trusted, relevant and linked-into the wider web ecosystem.