Updated on 9 November 2026 by Nicolas Finet, CEO of Sortlist. This checklist has been rewritten for 2026: it explains on-page SEO and what an on-page SEO service should cover, with current guidance on titles and meta descriptions (Google measures title links in pixels and rewrites weak ones), content quality, structured data, internal links and Core Web Vitals.
On-page SEO is everything you control on a page that helps search engines and people understand it: content, titles, headings, links, images, markup and performance. This guide gives a checklist you can use yourself or use to judge an SEO service.
Key takeaways
- On-page SEO covers content, HTML elements and page experience. Off-page SEO covers signals from other sites, mainly links and mentions.
- Google cuts desktop title links at about 600 pixels (roughly 50-60 characters) and often rewrites titles that are too long, boilerplate or mismatched with the page's H1 and content.
- Write for the reader first: match search intent, show real expertise and keep pages fast. Core Web Vitals thresholds are LCP 2.5 seconds, INP 200 milliseconds and CLS 0.1.
What is on-page SEO?
On-page SEO is the optimisation of individual pages so that they rank well and satisfy visitors. It includes the visible content and the code behind it. A page that is helpful, clear, fast and well structured is easier for search systems to understand and more likely to be chosen.
On-page SEO vs off-page SEO
| Area | On-page SEO | Off-page SEO |
|---|---|---|
| Where it happens | On your own pages | On other sites and platforms |
| Examples | Content, titles, headings, internal links, schema, speed | Backlinks, mentions, reviews, digital PR |
| Control | Direct | Indirect |
See how to get quality backlinks for off-page tactics.
On-page SEO vs local SEO
Local SEO focuses on visibility for searches with local intent, using Google Business Profile, citations, reviews and location pages. It overlaps with on-page SEO, since location pages and local content are on-page work, but it also depends on off-site profiles. See our Google SEO guide.
Why is on-page SEO important?
- It is within your control and does not depend on others.
- It helps search engines understand relevance.
- It improves user experience, which supports conversions.
- Improvements to existing pages are often faster than building new ones.
- It prepares your content to be cited in AI-generated answers by being clear, accurate and structured.
On-page SEO checklist
1. Keyword research and search intent
- Choose a primary phrase and related questions for each page. See focus keywords and keyword research tools.
- Check what ranks and what format it takes (guide, list, product page).
- Map each page to a distinct topic; avoid pages that compete.
2. Title tags
- Put the main topic first and the brand last.
- Keep it to about 50-60 characters. Length is measured in pixels, and Google truncates desktop title links at about 600 pixels.
- Make each title unique, specific and consistent with the H1 and content.
- Avoid boilerplate and keyword stuffing, which lead Google to rewrite titles.
“Length is measured in pixels, not characters; around 60 characters is a safe proxy. Front-load the words that distinguish the page; the brand goes last. Google rewrites titles that are too long, boilerplate, or mismatched with the H1 and content.”
Serion Flow, Title tag length and best practices
3. Meta descriptions
They are not a ranking factor but affect clicks. Summarise the benefit in around 150 characters, include a reason to click and write uniquely for each page. Google may rewrite them to match the query.
4. Headings and structure
- One H1 that states the page topic.
- H2s and H3s that follow a logical outline and answer likely questions.
- Short paragraphs, lists and tables where they help.
5. Content quality and E-E-A-T
- Answer the question completely and directly, with the answer near the top.
- Show experience and expertise: author names, credentials, original data, examples.
- Cite sources and date the content; update it when facts change.
- Avoid thin, duplicate or mass-produced pages: scaled content abuse is a spam policy violation.
6. URLs
Use short, readable, lowercase URLs with hyphens and the main topic. Avoid unnecessary parameters and change URLs only with proper redirects.
7. Internal links
Link to relevant pages with descriptive anchor text, and make sure that important pages are linked from others. See internal linking.
8. Images and media
- Use descriptive file names and meaningful alt text.
- Compress and use modern formats (WebP, AVIF) with set width and height.
- Lazy-load below-the-fold images, but not the main image.
- Add captions, transcripts and video where helpful.
9. Structured data
Mark up articles, products, reviews, events, local business and breadcrumbs with schema.org, matching what is visible on the page. Note that FAQ rich results are no longer shown; see FAQ rich results.
10. Page experience and Core Web Vitals
| Metric | Good threshold |
|---|---|
| Largest Contentful Paint (LCP) | 2.5 seconds or less |
| Interaction to Next Paint (INP) | 200 milliseconds or less |
| Cumulative Layout Shift (CLS) | 0.1 or less |
Also ensure mobile usability, secure HTTPS and no intrusive pop-ups.
11. Indexing controls
Check canonical tags, robots directives and noindex tags. See canonical tags. Submit an XML sitemap and monitor indexing in Search Console.
12. Calls to action and conversion
SEO only pays if visitors act. Make the next step clear and test layouts. See CRO agencies.
What should an on-page SEO service include?
| Deliverable | What you should receive |
|---|---|
| Page audit | Issues by page and priority |
| Keyword and intent mapping | A target phrase and topic for each page |
| Title, meta and heading rewrites | Implemented or supplied for approval |
| Content updates | New or improved copy, with an editorial brief |
| Internal linking plan | Links to add and pages to connect |
| Technical fixes | Speed, indexing and schema recommendations or fixes |
| Reporting | Rankings, clicks, conversions and a plan for next steps |
UK SEO retainers run from about £1,500 to £5,000 a month for growing businesses, according to 2026 guides. One-off audits cost less; see SEO audit prices and advanced SEO services. Be wary of guaranteed rankings.
Examples
| Before | After |
|---|---|
| Title: "Home | Acme Ltd | Services | Welcome" | Title: "Boiler Servicing in Leeds | Acme Heating" |
| H1: "Welcome to our site" | H1: "Boiler servicing in Leeds, from £75" |
| Image alt: "image1" | Image alt: "Engineer servicing a combi boiler in a Leeds kitchen" |
| Link text: "click here" | Link text: "book a boiler service" |
The examples are fictional.
Frequently asked questions about on-page SEO
What is on-page SEO?
The optimisation of content and HTML elements on a page so that it ranks well and satisfies visitors.
How long should a title tag be?
About 50-60 characters, as Google truncates at about 600 pixels on desktop. Put the main topic first.
Do meta descriptions affect rankings?
Not directly, but they influence click-through rate.
How much does on-page SEO cost?
UK retainers typically run about £1,500-£5,000 a month, and one-off audits and fixes cost less.
Is schema markup required?
No, but it helps search engines understand content and can enable rich results where available.
How often should I update pages?
Review key pages at least twice a year and whenever facts, prices or rules change.
Need on-page SEO help? Post your project on Sortlist and compare UK SEO agencies for free.
Sources: Serion Flow, title tags, LaunchScaler, title tag length, Google, Core Web Vitals, Rubik Digital, SEO cost UK. Examples are fictional.
