5 Technical SEO Mistakes Developers Still Make in 2025 (And How to Fix Them)

Let’s face it — in 2025, your website isn’t just a digital business card. It’s your best salesperson, your growth engine, and your 24/7 brand ambassador.

And while developers are the ones behind the scenes making the magic happen, even the most skilled devs still miss a few key things when it comes to SEO — especially the technical side.

That’s not a knock — it just means there's a gap between development and SEO that still needs bridging.

So, if you’re a developer (or working with one), this guide is your go-to checklist. Let’s dive into the 5 technical SEO mistakes developers still make in 2025 — and how to fix them before they cost you rankings, traffic, and conversions.

Mistake #1: Not Prioritizing Core Web Vitals

What’s the Issue?

In 2025, Core Web Vitals are no longer “nice to have” — they’re deal-breakers. These are Google’s key performance metrics, including:

1) LCP (Largest Contentful Paint) – loading speed

2) FID (First Input Delay) – interactivity

3) CLS (Cumulative Layout Shift) – visual stability

Many developers still focus on building beautiful features… but ignore how fast they load or how smoothly they behave.

How to Fix It:

1) Optimize images (WebP, lazy loading, compression)

2) Minimize JavaScript and CSS bloat

3) Use efficient caching strategies

4) Prioritize above-the-fold content

5) Use tools like PageSpeed Insights, Lighthouse, and Chrome DevTools regularly.

Mistake #2: Poor URL Structure & Dynamic Parameters

What’s the Issue?

Long, messy URLs with multiple parameters or no logical structure confuse both users and search engines.

Example of a bad URL:

www.example.com/product?id=54783&ref=xyz&utm_campaign=sale

It’s not descriptive. It's not clean. It’s a nightmare for crawling and indexing.

How to Fix It:

1) Stick to clean, readable URLs: www.example.com/product/organic-coffee

2) Use hyphens, not underscores

3) Avoid session IDs or unnecessary query strings

4) Implement canonical tags when necessary

5) Remember: Clean URLs = better SEO and a better user experience.

Mistake #3: Ignoring Mobile-First Development

What’s the Issue?

Since Google moved to mobile-first indexing, many developers still build for desktop first and “make it responsive” later.

That’s a backward approach in 2025.

With over 70% of traffic coming from mobile, if your site doesn’t work flawlessly on phones, you’re not just losing traffic — you’re losing business.

How to Fix It:

1) Design and test on mobile first

2) Use fluid layouts, flexible images, and scalable fonts

3) Avoid elements that aren’t touch-friendly (like tiny buttons or hover-only interactions)

4) Run your site through Google's Mobile-Friendly Test

5) Mobile isn’t optional. It’s the new standard.

Mistake #4: JavaScript Rendering Issues

What’s the Issue?

JavaScript frameworks like React and Angular are amazing for creating fast, dynamic websites — but they can wreck your SEO if not rendered correctly.

If search engine bots can’t see your content because it’s hidden behind JS, your page won’t rank — even if it’s brilliant.

How to Fix It:

1) Use server-side rendering (SSR) or static site generation (SSG) where possible

2) Implement dynamic rendering for bots, if SSR isn’t an option

3) Ensure crawlable HTML is available in the source code

4) Test using Google’s URL Inspection Tool in Search Console

5) Bonus: Use tools like Rendertron or Prerender.io to help bots read your JS content.

Mistake #5: Missing or Misusing Structured Data (Schema)

What’s the Issue?

Structured data (Schema.org markup) helps search engines understand the content on your page — like products, events, FAQs, and reviews. Without it, you're missing out on rich results like star ratings, featured snippets, and product info.

And sadly, many developers either:

1) Don’t use it at all

2) Use the wrong type

3) Or forget to update it

How to Fix It:

1) Use JSON-LD format (Google’s preferred)

2) Apply schema types based on your content:

 e.g., Product, Article, FAQ, LocalBusiness

3) Test it with Google's Rich Results Test

4) Keep it updated and error-free

5) Even a simple FAQ schema can drastically boost visibility in search results.

Bonus Tip: Keep SEO & Development Connected

One of the biggest missed opportunities?

SEO and development teams working in silos.

The best-performing websites are born when developers and Search engine optimization specialist collaborate early — not after launch, not as an afterthought.

So whether you’re building a new site or optimizing an old one, make SEO part of your code reviews, planning sprints, and QA process.

Conclusion: Don’t Let Small Mistakes Cost You Big Results

In 2025, technical SEO isn’t optional — it’s critical.

Even the sleekest, most beautiful site won’t rank if it’s:

1) Slow

2) Broken on mobile

3) Poorly structured

4) Invisible to search engines

These technical mistakes may seem small, but they stack up. And if your website isn’t visible, it's as good as invisible.

Here’s where A99 Solutions comes in.

At A99 Solutions, we don’t just build websites. We build digital foundations that grow with your business — fast, secure, optimized for search, and loved by users and Google bots.

From fixing core web vitals to optimizing JS-heavy frameworks and implementing rich Schema, our developers + SEO teams work in perfect sync.

Let us help you build a technically sound, search-friendly website that performs today and scales tomorrow.

Contact A99 Solutions for a free technical SEO audit