Technical SEO Services: What They Include and How to Choose

Technical SEO services fix the plumbing behind your website: the bits that decide whether Google can find your pages, render them, index them and show them to people. A good provider audits the site, sorts the problems by what they cost you in enquiries or sales, works with your developers to fix them without breaking anything, and then proves the result in your analytics. A weak one sends a 200-page crawler export and wishes you luck. This guide covers what the work includes, how a sensible audit is prioritised, what changes for shops and service businesses, and the questions to ask before you sign.

Not sure whether your site has a technical problem or a content problem? Castle’s in-house SEO team will tell you which, and what it’s worth fixing first.

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TL;DR

• Technical SEO covers crawling, indexing, rendering, site speed, structured data, mobile and migrations. Your content and links depend on it.
• A useful audit is validated by a person, scored on impact, confidence and effort, and comes with a test plan. A raw list of crawler warnings isn’t an audit.
• Shops need control of filter URLs, product markup in the initial HTML and fast category templates. Service businesses need fast, accessible pages and forms that actually work on a phone.
• Judge agencies on how they prioritise, whether they can work alongside your developers, and whether they report on enquiries and revenue.
• The same foundations decide whether AI search tools can read your site and cite it.

Table of Contents

• What technical SEO services actually are
• What a technical SEO service includes
• How a good audit prioritises problems
• What happens after the audit
• Technical priorities for ecommerce and lead-generation sites
• Technical SEO in Manchester and the North West
• Why technical health matters for AI search
• How to choose a technical SEO agency
• Our perspective
• Work with Castle on technical SEO
• FAQ
• Sources

What technical SEO services actually are

Content and links tell search engines what you sell. Technical SEO decides whether they can get to that information in the first place. If a key page is blocked, duplicated, slow to render or hidden behind scripts, the best copy on the site never gets a look in.

Search Engine Land’s guide puts it simply: technical SEO is making sure search engines can find, understand and display your website properly. Google’s own crawling and indexing documentation is the rulebook for most of it, covering sitemaps, robots.txt, canonical tags, JavaScript, redirects and site moves. A technical SEO service applies that rulebook to your platform, your templates and your commercial goals.

It helps to think in three layers:

• Access. Can crawlers find and fetch the pages that make you money?
• Understanding. Once fetched, can they render the content and read it correctly, through clean HTML, sensible canonicals and structured data?
• Experience. Do those pages load quickly, respond to taps and stay still while they load on a mid-range phone?

One honest caveat before going further. Technical work removes barriers; it doesn’t create relevance. Google’s page experience guidance says its systems always seek to show the most relevant content, even if the page experience is sub-par. A perfect Lighthouse score on a thin page will lose to a slower page that answers the question. Fix the plumbing so your best content can compete, then go and write the best content.

What a technical SEO service includes

Scopes vary, but credible services cover the following. If a proposal skips one of these, ask why.

Crawlability and indexation

This comes first. The work covers robots.txt, XML sitemaps, internal linking, redirect chains, 404s, orphaned pages and canonical tags, with one aim: crawlers should spend their time on pages that earn you money rather than on parameter URLs, empty filter pages or products you stopped selling in 2022.

Small details cause big messes here. Google treats URLs as case sensitive, so /Boots and /boots are two different addresses. Its URL structure guidance says that if your server treats them as the same, you should convert everything to one case, and it recommends trimming parameters that don’t change the content.

What about crawl budget? Most sites can relax. Google says its crawl budget guide is aimed at sites with over a million unique pages that change weekly, or over 10,000 pages that change daily, and that if your new pages are crawled the day they’re published you don’t need it. An agency that leads its pitch to a 60-page plumbing firm with “crawl budget optimisation” is selling you something you don’t need.

Site speed and Core Web Vitals

Google’s Core Web Vitals documentation sets three targets: Largest Contentful Paint within 2.5 seconds, Interaction to Next Paint under 200 milliseconds, and Cumulative Layout Shift under 0.1. In plain English: how quickly the main content appears, how fast the page reacts when someone taps a button, and whether things jump about while it loads. INP is the newest of the three; it replaced First Input Delay as a Core Web Vital in March 2024, and plenty of sites that passed the old test fail the new one.

The bar isn’t low. The HTTP Archive’s 2025 Web Almanac found that only 48% of mobile sites passed all three Core Web Vitals in its July 2025 data, against 56% on desktop. Loading was the weak spot, with just 62% of mobile sites achieving a good LCP.

A proper service tells you which templates fail, why, and what it would take to fix them. “Your PageSpeed score is 41” is a reading, not a diagnosis.

JavaScript and rendering

Google processes JavaScript sites in three phases: crawling, rendering and indexing. Its JavaScript SEO basics are blunt about the consequence: Google can only see content that’s visible in the rendered HTML. The same page says server-side rendering or pre-rendering is still a great idea because it makes the site faster for users and crawlers, and because not every bot runs JavaScript. If your product listings, prices or internal links only appear after scripts run, rendering goes to the top of the audit.

Structured data

Schema markup helps search engines interpret products, services, organisations, reviews and FAQs. For shops with colours and sizes, Google supports product variant markup using ProductGroup, with hasVariant for the individual variants, variesBy for the attributes that differ and productGroupID for the parent SKU. Google announced that support in February 2024.

Mobile, security and international setup

Mobile display, HTTPS, intrusive interstitials and the line between main content and everything else all sit in Google’s page experience checklist. If you sell into more than one country, hreflang belongs here too, and it’s one of the easiest things in SEO to get quietly wrong.

Migrations and replatforming

Redesigns, domain changes and platform moves are where rankings most often go to die. Redirect mapping, pre-launch testing and post-launch monitoring are core technical SEO tasks, not extras. If a migration is on your roadmap, bring your SEO provider in before the designs are signed off. After launch is too late to discover that 400 product URLs now redirect to the homepage.

How a good audit prioritises problems

Anyone can run a crawler. The value is in deciding what to fix first, and what to ignore.

Every finding should be checked by a person against more than one data source (the crawl, Search Console, analytics and ideally server logs) before it goes in the report. Crawlers flag plenty of things that don’t matter on your site and miss some that do.

Then it needs a score. One practical method, described in Search Engine Land’s guide to high-impact technical audits, is ICE: rate each recommendation on impact, confidence and ease of execution. The agency in that piece doubles the weight on impact (score = 2 × impact + confidence + ease), which we think is right. A fix that touches every product page should beat a tidy-up of three blog tags, even if the tidy-up is easier.

Here’s what each finding in a useful audit should give you:

• The issue: a plain description, with example URLs or the template name.
• The root cause: why it happens, for instance a plugin, a theme template or a server rule.
• The priority: a score based on impact, confidence, effort and how many pages are affected.
• The fix: instructions specific enough for a developer to build without a meeting.
• Acceptance criteria: how you’ll know the fix worked.
• Measurement: the page groups, queries or conversions to watch afterwards.

If an audit arrives as an unfiltered export of crawler warnings, nobody has prioritised it. You’ll pay for that later in developer hours spent working out what matters.

What happens after the audit

The audit is the start of the job. In her Search Engine Land piece on safely implementing high-impact technical SEO changes, Amsive’s Dayna Lucio argues that a clear recommendation, a test plan and stakeholder agreement are what move implementation forward, and recommends testing redirects in a development environment before launch, then checking them again after. That means your provider has to work alongside your developers (or theirs), on a staging site where possible, with a named owner for each task.

A sensible rhythm after the audit looks like this:

1. Quick wins. Low-risk, high-impact fixes such as collapsing redirect chains or correcting canonicals.
2. Template fixes. Speed, rendering and structured data changes that improve hundreds of pages at once.
3. Validation. Checking in Search Console and server logs that Google has seen and accepted the changes.
4. Monitoring. Alerts for new errors after each release, so a regression is caught in days rather than at the next quarterly review.
5. Reporting. Movement in indexed pages, organic enquiries and revenue, not just rankings.

For the reporting side, our guide to using Google Analytics to improve SEO shows how to connect technical changes to what visitors actually do.

Technical priorities for ecommerce and lead-generation sites

The right priorities depend on how the site makes money.

Ecommerce sites

• Filters and faceted navigation. A filter that helps a shopper isn’t automatically a page worth indexing. Google thought this was a big enough problem to publish dedicated documentation on crawling faceted navigation URLs in December 2024.
• Product markup in the initial HTML. Google’s documentation updates from 1 October 2024 recommend putting Product markup in the initial HTML for best results, and making sure your server can cope with the extra load if the markup is generated with JavaScript.
• Variants. Use ProductGroup markup so colours and sizes are understood as one product family rather than 30 near-duplicates.
• Speed on category and product templates. These carry most of your revenue, so audit them before the blog.

To see why filters matter, run the numbers (this is an illustrative example). Take a shop with 40 category pages. Give each category five colour filters, six sizes, four price bands and three sort orders, and every combination gets its own URL. That’s 40 × 5 × 6 × 4 × 3 = 14,400 crawlable URLs built on 40 pages you actually care about. Googlebot doesn’t know which 40 those are unless you tell it.

Our walkthrough of five ways to improve SEO on your ecommerce website covers the commercial side of this in more detail, and our ecommerce marketing service pairs the technical fixes with the campaigns that send buyers to those pages.

Lead generation and service businesses

Service sites are usually smaller, so the gains come from precision rather than scale. A useful real-world benchmark is what public bodies now write into their website tenders. Plumpton College’s invitation to tender for a new website, published in September 2025, asks for mobile-first responsive design with faster load speeds, a PageSpeed Insights score of 90 or more, WCAG 2.2 AA accessibility, GDPR and cookie compliance, and redirect planning for a migration of around 1,000 pages. A college isn’t your business, but that list is a decent checklist for any service site.

Forms deserve special attention. A page that ranks and then loses people on a broken or fiddly mobile form still costs you money, it just hides the cost better. If you serve several towns, each location page needs unique content, clean internal links and correct local business details, not the same template with the place name swapped. Our lead generation service connects those foundations to a measurable pipeline.

Technical SEO in Manchester and the North West

Searches such as “technical SEO Manchester” tell us many buyers want a team they can meet. That’s reasonable. Crawling, rendering and indexing work the same in Salford as in Shoreditch, but a regional team brings local context: multi-location structures for firms covering Greater Manchester, Cheshire and Merseyside, consistent business details across location pages, and someone who can sit in a room with your developers.

If you’re comparing regional options, our pages for SEO in Manchester, Cheshire and Liverpool show how we structure local work. For towns further out, our guide to SEO for Southport, Warrington and Chester businesses goes into more detail.

Why technical health matters for AI search

ChatGPT, Gemini and Google’s AI features draw on web pages to build their answers. If your pages are hard to crawl, slow to render or only make sense once JavaScript has run, you’re harder to read and harder to cite, and as Google’s JavaScript guidance points out, not every bot runs JavaScript in the first place.

That’s why we treat technical SEO as the base layer for generative engine optimisation and answer engine optimisation. For the wider picture, read our take on SEO in 2026, or see how AI SEO compares with traditional SEO.

How to choose a technical SEO agency

Plenty of agencies list technical SEO on their services page. A handful of questions separates the ones who do it from the ones who resell a crawler licence.

• Who does the work? Ask whether strategists and developers sit in one team or whether the build is outsourced. Handovers between suppliers are where technical fixes stall.
• How do you prioritise? Ask for a sample audit with its scoring. You want impact, confidence and effort against each finding, not a list of warnings.
• Can you work with our developers? A provider that writes clear tickets, reviews staging builds and tests after release will save you weeks.
• What do you report on? Rankings alone aren’t enough. Ask for reporting tied to enquiries, orders and revenue.
• How do you price? Retainers suit ongoing monitoring; fixed fees suit one-off audits and migrations. Ask exactly what’s included and who owns implementation, and get a written scope rather than comparing day rates.
• What happens with AI search? Ask how their technical work helps your pages get read and cited by AI tools, not only ranked in blue links.

Be wary of anyone who promises rankings by a date, won’t give you access to the tools and accounts, or can’t explain a finding without reading it off the report.

Our perspective

Most technical SEO fails at the handover, not the audit. Lots of agencies can produce a thorough report. Far fewer stay involved until the redirect rules are live, the templates are fast and the enquiries start to move.

That’s why we run technical SEO with one in-house team, so the people who find a problem sit with the people who help fix it and measure it. We tie our reporting to enquiries and revenue, because a clean crawl report has never paid anyone’s wages.

We’d also argue that technical SEO is the cheapest way into AI search. Sites that are easy to crawl, render and understand give ChatGPT and Gemini something they can read, and that’s the starting point for being cited. Our approach combines traditional SEO with GEO and AEO so one technical foundation does both jobs.

Work with Castle on technical SEO

Castle has been helping UK businesses get found online since 2014. Our technical SEO work sits alongside AI SEO, GEO, AEO, content, Shopify development and paid media, all delivered by one in-house team, so fixes don’t get lost between suppliers. You can see the full range on our services page.

Send us your site and your biggest worry about it, and we’ll tell you what we’d fix first.

Talk to our SEO team

FAQ

What is included in technical SEO services?

Typical work covers crawling and indexation, robots.txt and sitemaps, canonical tags, redirects, site speed and Core Web Vitals, JavaScript rendering, structured data, mobile usability and migrations. A good service also prioritises the findings, supports implementation and reports on the commercial result.

How long does technical SEO take to show results?

It depends on the problem and how quickly fixes are released. Removing a crawling or indexing barrier can show up once Google recrawls the affected pages, while template-level speed work usually needs development time first. Ask any provider for a phased plan with milestones you can check yourself in Search Console and analytics.

Do I need an agency or can my developers handle it?

Developers are essential for implementation, but technical SEO also involves decisions about what to index, how URLs should be structured and which fixes carry the most commercial value. Most businesses get the best results when an SEO team specifies and tests the changes and developers, in-house or agency, build them.

Is technical SEO a one-off project or ongoing?

Both exist. A one-off audit suits a site that has never been reviewed or is about to migrate. Ongoing monitoring suits sites that release changes often, such as online shops, because new code, plugins and content can bring old problems back after any fix.

Does technical SEO help with AI search visibility?

It supports it. AI tools rely on content they can access and understand, so crawlable, fast, well-structured pages give you a better chance of being used as a source. Technical work is the base; content and authority build on it.

Sources

• What is technical SEO? The definitive guide, Search Engine Land
• Crawling and indexing, Google Search Central
• Understanding page experience in Google Search results, Google Search Central
• URL structure best practices for Google Search, Google Search Central
• Optimize your crawl budget, Google
• Understanding Core Web Vitals and Google search results, Google Search Central
• Interaction to Next Paint is officially a Core Web Vital, web.dev (March 2024)
• Performance chapter, Web Almanac 2025, HTTP Archive
• Understand JavaScript SEO basics, Google Search Central
• Product variant structured data, Google Search Central
• Adding structured data support for product variants, Google Search Central Blog (February 2024)
• Latest Google Search documentation updates, Google Search Central
• 7 tips for delivering high-impact technical SEO audits, Search Engine Land
• How to safely implement high-impact technical SEO changes, Search Engine Land
• Plumpton College website invitation to tender, Find a Tender (September 2025)

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• 5 Ways to Improve SEO on Your Ecommerce Website
• SEO Beyond Liverpool: A Guide for Southport, Warrington and Chester Businesses
• AI SEO vs Traditional SEO: What Does Your Business Need?