How to evaluate a web design agency before you sign
A portfolio page and a sales call tell you what an agency wants you to see. Four checks — run in about five minutes, on the agency's own site, before you ever get on a call — tell you what they'll actually ship: view the page source, time the first response, search for structured data, and read the browser tab title. None of this requires technical knowledge beyond right-click → View Page Source.
Written by the Causal Labs engineering team · Published 18 August 2026
Check 1: View the page source
Right-click the agency's homepage → 'View Page Source' (or Ctrl/Cmd+U). Search the page for 'wp-content' or 'elementor' — if you see either repeated dozens of times, the site is built on WordPress with a visual page-builder plugin, not custom code. That's not automatically disqualifying — plenty of good sites run on WordPress — but it tells you what you're actually being sold when an agency's pitch emphasises 'custom design' or 'bespoke build'.
Also count the <script> tags (Ctrl/Cmd+F, search '<script'). Fifty or more on a marketing site is a real signal of unnecessary weight — every one is a network request and a piece of code the browser has to parse before the page is usable.
Check 2: Time the first response
Open the browser's DevTools (F12 or right-click → Inspect), go to the Network tab, and reload the page. Look for 'TTFB' (time to first byte) on the first document request — this measures server response time before any content even starts arriving. A fast, well-built site responds in well under 100ms; anything above 500ms usually means an unoptimised server stack, not just a distant data centre.
This matters commercially, not just technically: TTFB is part of what Google's Core Web Vitals measure, and a slow-responding site is a real, measurable ranking and conversion disadvantage — not an abstract engineering concern.
Check 3: Search for structured data
Back in View Page Source, search for 'application/ld+json'. This is structured data (JSON-LD) — machine-readable markup that helps Google understand what a page actually is, and increasingly, what AI tools cite when answering questions. A surprising number of professional-looking agency sites — including some agencies selling web design as their core service — ship zero structured data, on their own homepage. If an agency isn't doing this for themselves, ask directly whether they'll do it for you, and get it in the scope in writing.
Check 4: Read the browser tab title
Look at the actual browser tab, not the page content. A homepage titled just the company's own name, with no description of what they do or where, is a small but telling signal — that's the exact <title> tag Google shows in search results, and it's the single easiest SEO fix that exists. If an agency hasn't bothered to fix it on their own most important page, it's a reasonable question to ask how much SEO attention your site will actually get once the invoice is paid.
What good actually looks like
Put together: a fast, sub-100ms response on ordinary hosting: a full structured-data graph (organisation, services, breadcrumbs, FAQ markup where relevant); a specific, keyword-bearing page title, not just a brand name; and — if they claim custom design — page source that doesn't read as a stock page-builder plugin. None of these four checks require you to know how to code. They take about five minutes total, and they tell you more about what you'll actually receive than any portfolio screenshot.
Questions
Does a slow TTFB matter if the site is mostly static content?
Yes — TTFB measures server response before any content starts arriving at all, so it applies just as much to a static brochure site as a dynamic one. A slow response on simple content usually points to an unoptimised hosting stack, which tends to correlate with other corners cut elsewhere in the build.
Is WordPress itself the problem?
No — WordPress powers a huge share of the web and can be built well. The signal worth checking isn't the platform, it's whether the agency is honest about using a page-builder plugin (a legitimate, faster, lower-cost choice for the right project) versus marketing it as a fully custom build when it isn't.
How long should this whole evaluation actually take?
About five minutes for all four checks on one site. It's worth doing before the sales call, not after — it changes which questions are worth asking.
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