How to Choose a Technical SEO Agency

Choosing a technical SEO agency shouldn’t come down to who can produce the longest audit.

Most SEO tools can crawl a website and generate hundreds, sometimes thousands, of warnings within minutes. They’ll find broken links, missing metadata, redirects, slow pages, canonical issues and plenty of other things that look concerning in a spreadsheet.

Finding issues isn’t usually the difficult part. The difficult part is understanding which issues actually matter, why they’re happening and what should be fixed first.

That’s where a good technical SEO agency earns its value.

The right partner should be able to investigate how search engines discover, crawl, render and index your website, connect technical problems to their likely impact and work with developers to implement realistic solutions.

They should also know when not to recommend a change.

At ZEAL, we see technical SEO as a diagnostic discipline rather than a box-ticking exercise. A technically perfect score in an auditing tool isn’t the objective. Creating a website that search engines can access and understand while supporting users and commercial performance is.

So, how do you distinguish a thorough technical SEO agency from one simply exporting reports from the same tools everybody else uses? Here are the questions worth asking.

What Does a Technical SEO Agency Do?

A technical SEO agency specialises in identifying and resolving technical issues that can affect a website’s organic search performance. Depending on the website, its work might include:

• Technical SEO audits
• Crawlability analysis
• Indexation analysis
• Site architecture
• Internal linking
• Robots.txt
• XML sitemaps
• Canonicalisation
• Redirects
• HTTP status codes
• Duplicate content
• JavaScript SEO
• Structured data
• Core Web Vitals
• Website performance
• Mobile SEO
• International SEO
• Ecommerce SEO
• Log file analysis
• Website migrations
• Technical implementation
• Ongoing monitoring

That list can make technical SEO sound like a collection of individual checks, it isn’t. The real skill is understanding how those areas interact. An indexation problem might originate from poor internal linking. A crawl problem could be caused by faceted navigation. A performance problem might originate from design decisions or third-party scripts. A strong technical SEO agency investigates the cause rather than treating every symptom independently.

When Do You Need a Technical SEO Agency?

Not every website needs permanent access to a team of technical SEO specialists. For a small, straightforward website, many technical requirements can be handled within a broader SEO strategy.  Specialist support becomes increasingly valuable as complexity grows.

You may need a technical SEO agency if:

• Organic traffic has fallen unexpectedly
• Search engines aren’t indexing important pages
• You operate a large ecommerce website
• Your site uses significant JavaScript
• You’re planning a website migration
• You’re changing CMS or ecommerce platform
• You’re moving domains
• You operate internationally
• Your website generates large numbers of dynamic URLs
• Core Web Vitals are consistently poor
• Developers need specialist SEO guidance
• You’ve accumulated years of technical debt
• Previous audits have identified problems but nobody has implemented them
• Your SEO team can’t explain why particular technical problems are occurring

You may also bring in a technical SEO agency proactively. Finding migration risks before launching a new website is generally preferable to diagnosing a traffic decline afterwards.

Technical SEO Agency vs General SEO Agency

Many full-service SEO agencies provide technical SEO, that can work extremely well. The distinction is usually one of depth and focus rather than a completely different service.

A general SEO agency might work across:

• Technical SEO
• Keyword research
• Content
• Digital PR
• Link acquisition
• On-page optimisation
• Reporting

A specialist technical SEO agency may spend more of its time investigating areas such as:

• Crawling
• Rendering
• Indexation
• JavaScript
• Large-scale site architecture
• Log files
• Complex migrations
• Structured data
• International implementation

The right choice depends on the problem. If you need an entire organic search strategy, broader expertise may be valuable. If you have millions of URLs, complicated faceted navigation and unexplained indexation problems, deeper technical specialism becomes much more important.

Start by Understanding the Problem You’re Hiring Them to Solve

Before comparing agencies, define why you need one, perhaps organic performance has fallen, maybe you’re preparing for a migration, or your internal team has a backlog of technical recommendations that nobody has been able to prioritise.

Your brief could include:

• Current organic performance
• Known technical concerns
• Website platform
• Approximate site size
• International setup
• Important templates
• Recent migrations or development changes
• Existing SEO activity
• Development resources
• Commercial priorities
• Upcoming website changes

You don’t need to diagnose the problem yourself, that’s partly why you’re hiring specialists, but giving an agency context helps them determine the right scope.

1. Ask How They Approach a Technical SEO Audit

This is the obvious starting point.

Ask the agency to explain its audit process.

Be cautious if the answer is simply a list of tools.

Tools matter, but owning a Screaming Frog licence isn’t a methodology.

A good agency should be able to explain:

• What information it gathers first
• How it crawls the website
• Which first-party data it reviews
• How it investigates indexation
• How it identifies patterns
• How findings are validated
• How recommendations are prioritised
• How implementation is supported

The process should also change according to the website. Auditing a 50-page professional services website shouldn’t look identical to auditing an international ecommerce platform with hundreds of thousands of URLs.

2. Look for Diagnosis, Not Just Detection

This distinction is crucial.

Detection identifies something unusual.

Diagnosis establishes why it’s happening and whether it matters.

For example, a crawler might report:

8,000 non-indexable URLs found.

That sounds alarming.

A technical SEO specialist should ask:

• What are those URLs?
• Why are they non-indexable?
• Should they be indexed?
• How are crawlers discovering them?
• Are they receiving internal links?
• Are they in the sitemap?
• Is this behaviour intentional?

Perhaps those 8,000 URLs are filtered combinations that shouldn’t appear in search at all. In that case, “make them indexable” would be exactly the wrong recommendation. Good technical SEO requires context.

3. Ask Which Data Sources They Use

No single SEO tool provides a complete view of your website, a strong technical audit often combines several sources.

These might include:

• Website crawler data
• Google Search Console
• Google Analytics or other analytics platforms
• Page performance data
• Backlink data
• Ranking data
• Server logs
• CMS information
• Developer input

Different sources answer different questions. A crawler tells you how the website appears when systematically explored. Google Search Console provides first-party information about how Google is processing and surfacing the site. Analytics helps connect technical issues to real user and commercial behaviour. Server logs can show how search engine bots are actually crawling a website. The agency should know which source is appropriate for the question it’s trying to answer.

4. Ask How Deeply They Investigate Crawlability

Search engines need to discover and access pages before those pages can perform in organic search.

A technical SEO agency should therefore understand crawlability in depth.

That includes areas such as:

• Robots.txt
• Internal links
• XML sitemaps
• Crawl depth
• Orphan pages
• Redirects
• Broken links
• URL parameters
• Faceted navigation
• Crawl traps

For larger websites, the agency should also be able to distinguish between simply making pages crawlable and helping search engines spend their crawling activity sensibly.

Ask About Crawl Efficiency

Imagine your ecommerce website has 20,000 useful category and product pages but generates millions of filtered URL combinations.

The technical question isn’t simply:

Can Google crawl the website?

It’s also:

What is Google spending its time crawling?

That’s where deeper analysis becomes valuable.

5. Ask How They Analyse Indexation

Crawlability and indexation aren’t the same thing.

A page can be accessible to a search engine without being included in its index.

Your agency should be comfortable investigating:

• Which pages are indexed
• Which aren’t
• Whether important pages are missing
• Whether low-value pages are being indexed
• Noindex directives
• Canonicalisation
• Duplicate URLs
• Sitemap inclusion
• Google Search Console indexing reports

More indexation isn’t automatically better. The goal is for the right pages to be eligible for search. An agency recommending that every URL should be indexed probably isn’t asking enough questions.

6. Test Their Understanding of Canonicalisation

Canonicalisation is an area where simplistic recommendations can create problems. Ask how the agency investigates duplicate and near-duplicate URLs.

A thorough analysis may consider:

• Canonical tags
• Internal links
• Redirects
• Sitemaps
• URL parameters
• Product variants
• HTTP/HTTPS versions
• WWW/non-WWW versions
• Trailing slashes
• Pagination
• Filtered URLs

The canonical tag is only one signal. If your canonical says one thing while your internal links, redirects and sitemap say something else, you’re creating unnecessary ambiguity.

Good technical SEO looks at the complete set of signals.

7. Ask About JavaScript SEO

If your website relies heavily on JavaScript, this should form part of your agency evaluation.

Modern websites can use JavaScript to load:

• Content
• Navigation
• Products
• Internal links
• Metadata
• Interactive functionality

Search engines can process JavaScript, but complex implementations can introduce additional technical considerations.

A specialist agency should understand concepts including:

• Raw HTML
• Rendered HTML
• Client-side rendering
• Server-side rendering
• Hydration
• Crawlable links
• Rendering dependencies

Ask How They Test Rendered Content

A page looking correct in a browser doesn’t prove that search engines are receiving everything they need. The agency should be able to compare what exists in the initial HTML with what becomes available after rendering.

If your site is heavily JavaScript-dependent and an agency never discusses rendering, that’s worth questioning.

8. Assess Their Understanding of Website Performance

Website performance is both a technical SEO and user experience concern. A good agency should be able to investigate what’s making pages slow rather than simply telling you they’re slow.

Potential causes include:

• Images
• JavaScript
• Third-party scripts
• Fonts
• Server response
• Rendering
• Video
• Apps and plugins
• Tag management

Ask How They Approach Core Web Vitals

Technical SEO specialists should understand metrics including:

• Largest Contentful Paint (LCP)
• Interaction to Next Paint (INP)
• Cumulative Layout Shift (CLS)

But they should also understand the difference between laboratory testing and real-user data. A single PageSpeed Insights score doesn’t tell the entire story.

You want somebody capable of identifying why performance is poor and translating that diagnosis into something developers can act upon.

9. Ask About Structured Data Expertise

Structured data can help search engines understand entities and specific types of information on a page.

Depending on your website, that might involve markup relating to:

• Products
• Organisations
• Articles
• Breadcrumbs
• Events
• Jobs
• Local businesses

Your agency should be able to assess whether structured data:

• Is relevant
• Is valid
• Reflects visible content accurately
• Contains the necessary properties
• Is implemented consistently
• Creates template-level errors

Be cautious of anybody presenting schema as a guaranteed rankings shortcut.

Structured data helps search engines interpret content and can support eligibility for certain search features where applicable. It isn’t magic code for jumping to position one.

10. Ask About Their Ecommerce Technical SEO Experience

Ecommerce creates technical challenges that smaller websites may never encounter.

These can include:

• Faceted navigation
• Filters
• Product variants
• Pagination
• Out-of-stock products
• Discontinued products
• Category architecture
• Duplicate content
• Internal search
• Parameter URLs
• Large XML sitemaps

If you operate an ecommerce site, ask for relevant examples.

Don’t settle for: “Yes, we’ve worked with ecommerce.”

Ask what problems they solved:

• Did they work with faceted navigation?
• How did they handle discontinued products?
• How did they decide which filtered URLs should be indexable?

Specific answers reveal actual experience.

11. Ask About International SEO

International websites introduce another layer of technical complexity.

A specialist may need to consider:

• Country targeting
• Language targeting
• Hreflang
• International URL structures
• Canonicals
• Sitemaps
• Internal linking
• Localised content
• Redirects

Hreflang in particular can become complicated at scale. Ask prospective agencies how they audit and validate international implementations. If your international setup is commercially important, relevant experience should be more than a line in a capabilities deck.

12. Ask About Log File Analysis

Log file analysis isn’t necessary for every website, but it can be extremely useful for large or complex sites. Server logs can reveal how search engine bots are actually interacting with your website.

They can help answer questions such as:

• Which URLs is Googlebot requesting?
• Which sections are crawled frequently?
• Which are barely crawled?
• Are bots repeatedly encountering errors?
• Is significant crawling being spent on low-value URLs?

Ask whether the agency offers log analysis and, more importantly, when it thinks it’s useful. A good specialist won’t recommend complex analysis simply because it can.

13. Assess Their Migration Experience

Website migrations are one of the strongest reasons to involve technical SEO specialists.

A migration might involve changes to:

• Domain
• CMS
• Ecommerce platform
• URLs
• Site architecture
• Content
• Navigation
• Rendering
• Templates

Sometimes several change simultaneously, that creates risk.

Before Migration

A technical SEO agency may need to:

• Crawl the existing site
• Identify valuable URLs
• Record organic performance
• Review backlinks
• Plan new architecture
• Map redirects
• Review staging
• Validate templates
• Check indexation controls

During Launch

It may need to validate:

• Redirects
• Robots directives
• Canonicals
• Internal links
• XML sitemaps
• Analytics
• Search Console

After Launch

Monitoring should continue across:

• Crawl errors
• Indexation
• Rankings
• Organic traffic
• Redirect behaviour
• Server errors

Ask agencies to explain a migration they’ve managed and what safeguards they put in place.

14. Ask How They Prioritise Recommendations

This is one of the biggest differentiators between useful and frustrating technical SEO work.

An audit could uncover 500 issues and developers probably can’t fix all 500 tomorrow. Nor should they, a good agency needs a prioritisation framework.

That might consider:

• Impact – what could improve if this is fixed?
• Scale – how many important URLs are affected?
• Confidence – how certain are we that this is a genuine issue?
• Effort – what resources are required?
• Risk – could the fix have unintended consequences?

Ask to See an Example Deliverable

If possible, ask a prospective agency to show you an anonymised example with developer instructions.

Can you immediately tell:

• What’s wrong?
• Why it matters?
• Which URLs are affected?
• What should happen?
• How important it is?
• Who needs to fix it?

If not, imagine how your developers will feel.

15. Find Out Whether They Support Implementation

An audit is only valuable when useful recommendations turn into improvements, ask what happens after the report is delivered.

Does the agency:

• Brief developers?
• Join technical calls?
• Write tickets?
• Provide acceptance criteria?
• Review proposed solutions?
• Test implementation?
• Monitor the outcome?

Or do they email a spreadsheet and disappear? Implementation support is particularly valuable when recommendations are complex.

Technical SEO Should Be Collaborative

Developers understand your technology, SEO specialists understand the search implications. Neither should treat the other as an obstacle. Sometimes a developer will propose a better solution than the SEO originally suggested, that’s good. The objective is the outcome, not protecting somebody’s recommendation.

16. Ask Whether They Can Implement Changes Themselves

Some technical SEO agencies are advisory, others have development capabilities. Either model can work, what’s important is understanding responsibilities.

If the agency doesn’t implement fixes, establish:

• Who will?
• How will recommendations be communicated?
• Will the SEO agency work directly with developers?
• Who tests completed changes?
• Who resolves disagreements about implementation?

If you don’t have internal development capacity, an audit containing recommendations that nobody can implement has limited value.

17. Ask How They Communicate With Developers

This is worth assessing separately, a recommendation like: “Fix canonical tags”isn’t particularly useful.

Developers may need to know:

• Which templates are affected
• What the current behaviour is
• What the desired behaviour is
• Example URLs
• Edge cases
• Acceptance criteria
• How the fix will be tested

Strong technical SEO agencies can translate search requirements into actionable development work. That often matters as much as finding the issue itself.

18. Ask How They Validate Completed Fixes

Implementation shouldn’t be assumed successful because a development ticket has moved to “Done”. Changes need testing.

The agency should confirm:

• Was the recommendation implemented correctly?
• Did it affect all intended templates?
• Did it introduce new problems?
• Does the live site behave as expected?
• Are search engines responding as expected over time?

Technical SEO is often cyclical: Diagnose → recommend → implement → test → monitor.

Skipping the testing stage leaves the job unfinished.

19. Ask How They Measure Technical SEO Success

Technical SEO measurement can be nuanced, not every fix creates an immediate rankings increase. Some changes remove risk, some improve crawling, some consolidate signals. While others enable content to be indexed for the first time.

Useful measures might include:

• Indexation improvements
• Crawl behaviour
• Reduction in important errors
• Core Web Vitals
• Organic traffic
• Organic conversions
• Rankings
• Search visibility
• Pages receiving organic traffic

Metrics should connect back to the reason the work was undertaken.

Don’t Judge Success by Site Health Score Alone

Improving an auditing tool’s health score from 86% to 99% might look impressive, but what changed commercially? If the remaining 1% contains a serious problem affecting your most valuable pages while the other fixes were cosmetic, the score doesn’t tell you much. Tools provide indicators, they aren’t business outcomes.

20. Ask How They Deal with Competing Priorities

SEO doesn’t operate in isolation, your development team might simultaneously be working on:

• New products
• Customer features
• Security updates
• Conversion improvements
• Operational integrations
• Bug fixes

Your technical SEO agency needs to work within that reality, recommendations should therefore explain enough impact to help product and development teams prioritise them against other work. “SEO says it’s important” isn’t a business case.

21. Assess Their Reporting

Technical SEO reporting should help you understand progress without requiring you to become a crawler specialist.

Useful reporting might cover:

• Work completed
• Significant technical changes
• Outstanding priorities
• Implementation status
• Organic performance
• Emerging issues
• Next actions

The level of detail can vary according to audience, a developer may need specific technical evidence, a marketing director may need to understand impact and priorities.  A good agency should communicate effectively with both.

22. Ask Who Will Actually Work on Your Account

Technical SEO expertise often sits with particular people rather than an agency logo, find out who will perform the work.

Ask:

• Who conducts the audit?
• Who leads technical strategy?
• Who attends developer calls?
• Who reviews complex issues?
• How experienced are they?
• What happens if your main contact is unavailable?

This matters particularly when the sales process involves senior specialists. You should understand whether those people remain involved after the contract is signed.

23. Look for Relevant Experience

Technical SEO problems differ dramatically according to website type, relevant experience can therefore be extremely valuable.

If you operate a large ecommerce website, look for evidence around:

• Faceted navigation
• Product variants
• Crawl management
• Large-scale migrations

If you run an international site, look for:

• Hreflang
• Regional architecture
• International migrations

If you use a JavaScript-heavy framework, look for experience diagnosing rendering and indexing. You don’t necessarily need an agency that’s worked in your exact industry, you need one that’s solved technically comparable problems.

24. Ask About Their Tools — But Focus on How They Use Them

Technical SEO agencies may use tools including:

• Screaming Frog
• Sitebulb
• Google Search Console
• PageSpeed Insights
• Lighthouse
• Ahrefs
• Semrush

There may also be proprietary crawling, monitoring or reporting systems, that’s useful. But tools shouldn’t be the main reason you hire an agency, you could buy access to many of them yourself.

You’re paying for expertise in deciding:

• What to investigate
• How to configure the analysis
• What the data means
• What matters
• What doesn’t
• What to do next

A carpenter isn’t good because they own a saw. They’re good because they know how to get the best use out of the saw.

25. Look at How They Talk About Google

Be cautious around absolute claims. Technical SEO involves understanding search engine documentation, testing, evidence and experience. But agencies don’t have a secret switch inside Google.

Warning signs include claims such as:

• “We can guarantee rankings.”
• “This fix will definitely put you first.”
• “Google always does X.”
• “Our proprietary technique forces Google to index pages.”

Good specialists are comfortable with nuance, they’ll distinguish between documented behaviour, observed patterns, testing and informed hypotheses. A lot of SEO best practice has been learned through trial and error, so honest uncertainty can actually be a sign of expertise. It shows that an agency understands where the evidence ends and interpretation begins.

26. Ask About Monitoring

A technical audit gives you a snapshot, but websites do not exist in snapshots. Websites change, developers deploy updates, products disappear, plugins change, content teams publish new pages, redirects accumulate, new functionality is introduced. As such, “solved” technical problems can return.

Ongoing monitoring can help identify issues such as:

• Important pages becoming non-indexable
• New 404 errors
• Sitemap problems
• Canonical changes
• Performance regressions
• Server errors
• Unexpected indexation changes

Ask what your agency monitors between larger audits and how quickly significant issues are escalated.

27. Compare Pricing Based on Scope, Not Just Cost

Technical SEO proposals can vary considerably, one agency may offer an automated crawl with limited commentary.

Another may include:

• Discovery
• Multiple crawls
• Search Console analysis
• Analytics
• Log files
• JavaScript investigation
• Detailed recommendations
• Developer workshops
• Implementation support
• Validation

Those aren’t equivalent services, ask exactly what you’ll receive.

Questions About Price

Clarify:

• Is the audit fixed-fee?
• Is implementation support included?
• Are developer calls included?
• Is post-implementation testing included?
• Is ongoing monitoring separate?
• What happens if the investigation uncovers a larger problem?

The cheapest audit can become expensive if it doesn’t tell you what to do.

28. Red Flags When Choosing a Technical SEO Agency

• Every Audit Looks the Same
  Different websites have different technical risks.
  A rigid checklist with no adaptation should concern you.
• They Focus on the Number of Errors
  More detected errors don’t mean a better audit.
  Prioritisation matters.
• They Can’t Explain Why Something Matters
  “Because the tool says so” isn’t a technical SEO strategy.
• They Never Look at Search Console
  Crawler data alone doesn’t show how Google is actually processing your site.
• They Ignore Developers
  If implementation requires development, developers need to be part of the conversation.
• They Guarantee Rankings
  No responsible technical SEO agency can guarantee a particular ranking outcome.
• They Treat Every 404 as a Disaster
  Not every missing page needs redirecting, sometimes a 404 is the correct response. Context matters.
• They Want to Fix Everything
  Some audit warnings are harmless, some are extremely low priority. A specialist should know the difference.
• They Don’t Validate Their Recommendations
  Technical changes can have unintended consequences, testing matters.

29. Questions to Ask a Technical SEO Agency

When comparing agencies, ask questions that reveal how they think rather than simply what they sell:

• How do you approach technical SEO audits?
• How does your process change for different websites?
• Which data sources do you use?
• How do you analyse crawlability?
• How do you investigate indexation?
• How do you approach JavaScript websites?
• Do you offer log file analysis?
• How do you audit Core Web Vitals?
• What ecommerce technical SEO experience do you have?
• What international SEO experience do you have?
• How many migrations have you supported?
• How do you prioritise recommendations?
• Can we see an anonymised audit example?
• Do you write developer tickets?
• Will you speak directly with our developers?
• Can you implement fixes?
• How do you validate completed work?
• How do you measure success?
• What monitoring do you provide?
• Who will actually work on our account?
• How do you report progress?
• What’s included in the fee?

The answers should leave you with a clear understanding of what happens after you’ve appointed them.

How to Compare Your Technical SEO Agency Shortlist

If you’re comparing several providers, use consistent criteria.

Weight those factors according to your situation. For a major migration, migration experience and implementation support may deserve the greatest weight. For a large ecommerce website, crawl management and indexation expertise could be more important.

Choose for the problem you actually have.

Choose an Agency That Can Tell You What Matters

Technical SEO has no shortage of data, run enough tools and you can produce spreadsheets containing tens of thousands of URLs, hundreds of warnings and enough coloured charts to fill an entire board meeting.

That’s not the difficult bit, the difficult bit is answering:

1. What’s actually wrong?
2. Why is it happening?
3. Does it matter?
4. What should we do about it?
5. What should we fix first?

At ZEAL, our approach to technical SEO combines specialist crawling, first-party search data and human analysis to understand what’s genuinely limiting a website. We prioritise recommendations according to their likely impact, work alongside development teams to turn them into practical changes and validate the implementation afterwards.

If you need deeper technical SEO expertise, are preparing for a migration or have an audit full of recommendations that nobody quite knows what to do with, get in touch with ZEAL.